Friday, July 31, 2015

Storm Surge, A Hurricane's Greatest Threat

By: Dr. Marshall Shepherd , 3:46PM,GMT on July 30,2015

Even though you see reporters blowing in the wind and debris flying down the street during hurricane coverage, the greatest threat is storm surge. If you think back to Hurricane Sandy or Camille, the legacy of storm surge is quite apparent.

We've invited 2 of the top hurricane and storm surge experts in the world to join us on Weather Geeks this Sunday. I like the way Executive Producer and Meteorologist Mike Chesterfield characterizes the guests. He writes:

"Jamie Rhome: Storm Surge Specialist At the NHC /Team Lead Of the Storm Surge Unit At the National Hurricane Center (NHC)

When it comes to surge Jamie is THE guy.....Jamie Rhome worked on the development of the prototype Storm Surge Watch/Warning graphic (being introduced this year) and the storm surge inundation mapping (continues experimentally for a second year this season). Although storm surge has always been a concern along our coastline and to NOAA/NWS, the attention brought by Sandy's flooding gave us the boost to accomplish more and in less time, as evident by these new products.

Michael Lowry: Hurricane Specialist and Storm Surge Expert at The Weather Channel
Michael Lowry - Prior to his time at The Weather Channel, Michael spent time working at the NHC and worked directly with Jamie and his team helping in the development of some of the new surge product."

This show promises to live up to WxGeeks' standards: solid guests, amazing graphics, and something you may not have known before the show.

Please join us Sunday at Noon ET (11 CT, 10 MT, 9 PT)..

Also future episodes in August feature the amazing weather photography of storm chaser Roger Hill (August 9th) and a look inside FEMA's Hurricane Program with Rebecca Jennings as we continue towards the peak of the Atlantic basin hurricane season.

Follow @WxGeeksTWC or @DrShepherd2013 on Twitter.

Find us on Facebook at WxGeeks (Link) or Dr. Marshall Shepherd (Link)

El Nino and its Impacts on Atlantic Hurricanes

By: Dr. Phil Klotzbach , 5:49PM,GMT on July 30,2015

At this point, just about everyone has heard that a strong El Niño is underway. El Niño is simply warmer-than-normal sea surface temperatures (SSTs) in the central and eastern tropical Pacific Ocean that occurs about every three to seven years, on average. This El Niño can be clearly seen by looking at a recently-updated map showing SST anomalies (departures from normal):

Figure 1. Current SST anomalies across the Pacific Ocean. (NOAA)

El Niño impacts more than just water temperatures at the surface. A series of buoys monitors temperature anomalies at various depths in the ocean as well, and their current analysis shows anomalously warm sub-surface water in the eastern tropical Pacific, with cooler-than-normal in the western tropical Pacific. This type of water temperature pattern is typical for robust El Niños.

Figure 2. Observed mean (top panel) and anomalous (bottom panel) temperatures in the top 500 meters of the ocean across the tropical Pacific. (NOAA)

What does an El Niño do to the large-scale atmosphere/ocean circulation? Basically, it shifts where deep thunderstorms typically form in the tropical Pacific (near Indonesia) closer to the International Date Line. This alters lower- and upper-level wind patterns as shown in the schematic below. These altered lower- and upper-level wind patterns are the primary reason why El Niño typically results in reduced Atlantic hurricane activity (more on this later).

Figure 3. Schematic showing the typical atmospheric and oceanic response to El Niño events. (NOAA)

How does this El Niño compare with prior events?

As we go back in time, there is more uncertainty in the data, but we can be relatively confident that observations are reliable since 1950. One region that is typically referenced to measure the intensity of El Niño events is the "Nino 3.4" region. This region is defined to be 5°S-5°N, 170°-120°W and its location, along with several other adjacent regions which are also monitored, are shown in the figure below:

Figure 4. Location of several regions used to monitor the strength of El Niño

At the end of June, the SST anomaly was +1.0°C in the Nino 3.4 region, which was the 2nd warmest June value since 1950, trailing only 1997. The 1997/1998 El Niño event is generally considered to be the strongest El Niño of the 20th century. While final July SST values will not be available for several more days, the Climate Prediction Center provides weekly values. Using these values as estimates for the monthly value for 2015, it appears that 2015 will remain slightly behind 1997 for the strongest El Niño since 1950 for July. While not quite up to the magnitude of 1997, this still qualifies 2015 as the 2nd strongest El Niño since 1950 for the month of July.

Figure 5. July Nino 3.4 values from 1950-2015 as calculated from ERSSTv4 data. 2015's value is estimated from weekly SST data provided by the Climate Prediction Center.

What is the Forecast?

The latest forecast from the European Centre for Medium Range Weather Forecasts (ECMWF) indicates that this year's El Niño event is likely to eclipse the 1997 event by the end of the summer. The ECMWF, though very skillful, tends to be aggressive at developing El Niños, but any way you look at it, this year's event is going to be one of the strongest of the past 65 years.

Figure 6. Ensemble forecast from the ECMWF model for the Nino 3.4 region through January 2016. Each red dot represents one of fifty ensemble members. 1972, 1982 and 1997 are the third, second and strongest El Niños, respectively, since 1950.

How Does El Niño Affect the Atlantic Hurricane Season?

The remaining portion of this blog will briefly discuss the impact of El Niño on Atlantic basin hurricane activity. This relationship was first discovered by Dr. Bill Gray, founder of CSU's seasonal hurricane forecasts, and was first published in 1984. Increased upper-level westerly winds associated with El Niño increase vertical wind shear (the change in wind direction with height in the atmosphere) and tear apart hurricanes trying to form in the Atlantic. The figure below shows typical levels of vertical shear in the Atlantic Main Development Region (MDR) experienced in both El Niño and La Niña conditions (cooler than normal water in the eastern and tropical Pacific).

Figure 7. Typical vertical wind shear patterns experienced in El Niño and La Niña conditions, respectively.

These impacts of vertical wind shear are typically strongest in the Caribbean basin, which is the closest part of the Atlantic to the center of action of El Niño. 30-day-averaged vertical wind shear anomalies in the Caribbean are currently much stronger than any year since 1979.

Figure 8. Vertical wind shear anomalies in the Caribbean by year since 1979. Anomalies were calculated from the Climate Forecast System Reanalysis (CFSR) (through 2010) and the Climate Forecast System (CFS) version 2 analysis (2011-2015).

The impacts of El Niño are not uniform over the course of the Atlantic hurricane season. One way that we typically define hurricane seasons is through the Accumulated Cyclone Energy (ACE) index. This index convolves the frequency, intensity and longevity of storms into one number. It gives you a better idea of how active a hurricane season is than just looking at the frequency of storm formations. Typically, the end of Atlantic hurricane seasons is dictated by when vertical wind shear values become too strong, and consequently, we would expect El Niño to have more dramatic impacts on late-season ACE values. This turns out to be the case, when examining average ACE levels by month. While there are reductions in August and September ACE levels as well, the biggest differences are seen in October and November ACE. Eight times more ACE occurs in La Niña Octobers compared with El Niño Octobers based on historical data back to 1950.

Figure 9. Impact of El Niño, neutral (near-average tropical Pacific SSTs) and La Niña on Atlantic hurricane activity as measured by ACE by month.

Given the magnitude of this year's El Niño event, we would expect to see a quick end to this year's hurricane season in the Atlantic. Of course, just because a below-average Atlantic basin hurricane season is predicted, it does not guarantee no significant US impacts. Examples of below-average seasons with significant US impacts include 1965 (Hurricane Betsy), 1972 (Hurricane Agnes), 1983 (Hurricane Alicia) and 1992 (Hurricane Andrew). It just takes one hurricane hitting your home to make it an active season for you!

Cool Down Slowly Begins – Are You Interested in Weather?

By: Steve Gregory , 8:11PM,GMT on July 31,2015

(Next Regular WX Update MONDAY – AUG 3)

NOTE: You can follow me on TWITTER @WX_INTEL
 (One reason to follow: I Tweet right after posting a New WU Blog)


The Tropics are ‘stirring’ but not by much!

Currently, the only disturbance of note is INVEST 94L now several hundred miles to the WSW of the Cape Verdes, with estimated MAX winds of 20Kts. This system is really entangled up within the ITCZ which has become stronger / better defined over the far eastern ATL on into west Africa. At the same time, and as is typical by this time of year, the SAL has both weakened and remains north of 15˚N latitude. In addition, SST’s are now warm enough to support moderate convection, and according to CIMSS, wind shear near the system has fallen to near 10Kts.

While this more conducive environment for cyclone formation would seem to support some development of 94L, the entanglement with the ITCZ is undoubtedly inhibiting development, as is a generally stable environment just north of the rotational centroid. So while the Specialized Hurricane models still point towards slow development over the next 5 days – the system is likely to encounter more hostile conditions for development as it heads WNW. For this reason, my forecast continues to project ~10% chance for development into a Tropical Storm during the next 5 days.

Upstream from 94L is a more vigorous TW about 2 days away from reaching the African coast. This next system has a somewhat greater chance for development by the end of next week as it moves westward over the eastern ATL as the latest global models call for a major weakening to the SAL, along with a far more benign wind shear environment.


While I normally don’t cover Hurricanes outside of the ATL basin – Hurricane Guillermo about 1,800NM SE of the Big Island is worth monitoring – but remains at least 5 days away from becoming any threat to the state.


Both the GFS and ECMWF operational and ensemble models are in very good to excellent agreement on the evolving upper air pattern during the next 10-15 days, with the development of a long wave TROF over the eastern US and a building sub-tropical ridge over the inter-mountain west.

This will bring a slow but steady cool down to the Midwest and much of the east during the week ahead, while well above normal Temps expand and intensify some over the west – a very similar upper air pattern to what existed during much of June.

The cold front marking the leading edge of the cooler and drier air will manage to reach into the SE US westward into TX. However, the main impact for the Gulf coast states will not be cooler Temps – but hotter ones! The drier and far more stable air that will infiltrate into the southern states will bring clear skies during daylight hours, with the stronger solar insolation sending Temps higher than they normally would go during the summer when the air is moist and generally unstable - which normally leads to more afternoon cloudiness - capping the afternoon Temp rise.

Once this pattern becomes established later next week, no major changes are expected to it during Week 2, and possibly into the third week of August as well.


With the aforementioned pattern change, we are already seeing rising upper level heights over Alaska, with the main storm track shifting further south, allowing a general warm-up across much of the state during the week ahead. But late next week, a secondary storm track should begin developing over the Arctic Ocean, with surface storms passing just north of the state. And by late Week 2, a more general storm track from near Kamchatka and the Bering Sea eastward into the state will likely lead to a wetter and bit cooler period by mid-month. (All of which is seasonally typical.)


A number of people have asked me about any options for ‘online learning’. One of the BEST I know of is the COMET Educational Program offered by UCAR . There are scores of learning modules, with the most recent course addition Introduction to Meteorological Charting

Best of all – it’s free.

CLICK IMAGE to open full size image in a new window

Fig 1: Color Enhanced IR (infrared) image of the Tropical Atlantic. The main area of interest is in vicinity of INVEST 94L, several hundred miles WSW of the Cape Verdes. The leading TW near 46˚W longitude is moving thru a very stable environment, with the SAL following immediately behind the wave axis. The TW that gave rise to 94L itself has been unable to out run the sudden resurgence in the ITCZ, where a very broad rotation can be seen on the TPW imagery loop (see below). For a variety of reasons, wind flow analysis near/within the ITCZ can be very deceiving, and in reality, tropical cyclones cannot actually form within it. On rare occasions, however, disturbances have been able to migrate far enough away from the ITCZ to develop – but this is both a rare event and virtually impossible to forecast accurately. Just now entering our image view is the strongest T-storm cluster of the season associated with a developing TW. This system is also closely tied with the ITCZ, but model projections do call for the system to eventually move to near the Cape Verdes and then slowly westward by late next week. Something to watch…

Fig 2: The TPW (Total Precipitable Water) Loop (Top) and latest image frame (bottom) highlights areas with deep layered moisture. ‘Bluish’ colors represent dryer air while the darker, ‘orange’ tones highlight areas of deep moisture in the column of air above the surface. The 72 hour looped imagery shows a decidedly strong increase in deep layered moisture within the ITCZ itself over the EATL, with a ‘rotational’ flow observed in vicinity of INVEST 94L.

>Fig 3: Color Enhanced IR (infrared) image focused on INVEST 94L, along with the satellite derived wind shear analysis. The ITCZ is clearly seen extending west-to-east with areas of moderate convection (Cloud top Temps are near -65˚C within some of the heaviest convection – indicating cloud tops of over 50,000ft). Wind shear is a relatively low 10Kts near INVEST 94L, but as mentioned above, automated wind analysis near the ITCZ is often problematic.

>Fig 4: CIMSS SAL analysis (that tends to highlight dry air vs ‘dust’ per se) – with satellite derived low-mid level wind vectors. There is virtually no indication of a low level circulation associated with 94L, though the system remains about 200NM south of the SAL. Model track projections currently track the system closer to the SAL, and any attempts at intensification will be more than offset by dry air entrainment IMO.

Fig 5: Track and Intensity Forecasts from several specialized Hurricane Models that were run early today for INVEST 94L. These models are all used for fairly shallow systems (typical for systems that are weak cyclones or open waves as is the case now). Once again, the built-in biases of these models (especially CLP5 which is a ‘climatologically’ based model) continue to show very slow development over the next 5-days. As noted above, however, it is very unlikely INVEST 94L will ever become a cyclone.

Fig 6: 96 Hour Forecast for Dust Transport Stepping back out to the ‘big picture’, we find dust density within the SAL flow decidedly lower, with a forecast calling for virtually no dust transport at all by early next week! If this forecast pans out – the negative impact of the SAL on the next TW will be insignificant. It remains to be seen, however, if this development is correct and whether it really means the end of ‘SAL Season’ is upon us.

Fig 7: Visible image of Hurricane Guillermo Guillermo, still a week away from being any threat to Hawaii – is estimated to have sustained winds of 80Kts – and will likely attain CAT 2 Intensity within the next 12-36 hrs. Worth keeping an eye on…

Fig 8: GFS Jetstream Forecast for next 2 Weeks. At the beginning of the forecast period, we find the sub-tropical high still centered across the far south central US, with a large TROF across southern AK and GOA, and the developing long wave TROF with its axis now extending from near Hudson Bay Southeastward towards the eastern Great Lakes. By the middle of next week, weak ridging can be seen in vicinity of Alaska, while the eastern TROF will likely de-amplify somewhat as the next short wave TROF out of NW Canada starts digging southeastward towards the Great Lakes – ultimately leading to re-amplification of the eastern TROF during Week2 (around Day 10-12). In addition, by the end of the loop – we see a marked increase in jet stream winds near Alaska along with a developing large upper air Low approaching the NW portion of the state as the sub-tropical high over the US becomes the dominant upper air feature over the lower 48. .

Fig 9: Temperature ANOMALY forecast for Week 1 is based STRICTLY on the MOS data forecasts from the todays 12Z operational GFS model run with minor adjustments towards the raw model data points. Above normal readings across much of the nation as cooler Temps are felt from the northern Plains to upper Midwest and interior Northeast. While still above normal in TX – much drier air will ease the discomfort level there and across the SE. Confidence in the forecast anomaly Pattern and magnitude is solidly above average now, with readings of ‘5’ and ‘4’ on a Scale from 1 to 5 for the anomaly pattern and magnitude respectively.

Fig 10: Running Precipitation totals for US during Week 1 (and only for totals > 0.75”) based STRICTLY on the GFS Heaviest Precip will a likely shift a bit further south across the SE states, while a series of cold fronts will trigger T-storm activity from the Midwest/Great Lakes and Ohio Valley – eastward to the Mid-Atlantic states. A decidedly drier period lies ahead for Alaska.

Fig 11: The Week 2 Temperature ANOMALY forecast is based on the 12Z run of the GFS (70%) integrated with the 12Z GFS Ensemble (30%) using the projected pattern along with explicit surface and 850mb (~5,000 FT) Temp forecasts. Some Temps are adjusted for known / expected anomalous thermal patterns & projected storm system passages.A much cooler pattern over the eastern half of the nation – while well above normal Temps develop across most of the interior West. Confidence in the forecast anomaly Pattern and magnitude is now closer to average by summer standards – with reading of ‘3’ for the overall anomaly pattern, but still only a ‘2’ for the magnitude on a Scale from 1 to 5.

Fig 13: Today’s Temperature anomaly forecasts are based on the 12Z run of the Operational GFS using the GFS MOS data A much warmer period ahead with drier conditions in most areas. Anomalies are likely to remain on the positive side of normal during Week 2 – but not much as cloudiness and more Precip returns to the state.

✭ The Next REGULAR Weather Update will be MONDAY, AUGUST 3 (SOONER if INVEST 94L Develops)

‘Normal’ Summer Update Schedule is MON, WED & FRI - but can vary by a day or so
However, whenever Tropical Cyclones Potentially threaten the US, I’ll be providing Updates 1 or more times per day



1. A GENERAL Glossary of Weather Terms can be found HERE

2. Another Glossary of weather terms is available HERE

Guillermo Gathers Steam in NE Pacific; Invest 94L Clings to Life

By: Bob Henson , 5:54PM,GMT on July 31,2015

Hurricane Guillermo is stepping up its game in the Northeast Pacific, as it moves along a steady west-northwest course that could bring it near the Hawaiian Islands next week. Guillermo was upgraded to hurricane status by the National Hurricane Center at 5:00 am EDT Friday, and in the NHC’s 11:00 am EDT advisory, Guillermo was located at 12.4°N, 132.7°W, with top sustained winds at 90 mph. Visible and infrared satellite imagery shows a healthy tropical cyclone, with extensive upper-level outflow, a distinct convective core, and a small eye beginning to take shape. Guillermo is successfully fending off an expanse of dry air to its north and maintaining an envelope of rich moisture.

Figure 1. A GOES West infrared satellite image of Hurricane Guillermo from 1630 GMT (12:30 pm EDT) on Friday, July 31. Image credit: NOAA/NESDIS.

Guillermo is in a quite favorable environment to intensify further, with warm sea-surface temperatures and low wind shear. SSTs are around 28-29°C (82-84°F) along Guillermo’s path for the next day or so, which is 1-2°C above the climatological norm (see Figure 2). The oceanic heat content--the amount of energy in the uppermost part of the ocean--is rather low ahead of Guillermo, which could spell trouble for a slow-moving system churning up cooler water from below (see Figure 3). However, Guillermo is moving briskly (about 17 mph), and that pace is expected to continue for the next couple of days.

Figure 2. Departures from average sea-surface temperature over the Northeast Pacific for the week ending July 27, 2015. Image credit: NOAA National Hurricane Center.

It is still too soon to know how much of a threat Guillermo will pose to the Hawaiian Islands. The steering flow around Guillermo will be fairly stable over the next several days, keeping it on a track headed almost directly toward the islands. The NHC’s latest outlook places Guillermo located about a day away from the Big Island by early Wednesday morning. The most recent track models are in some disagreement over whether Guillermo will be picked up by a strong band of upper-level westerlies around this point, taking it well northeast of Hawaii; continue on its west-northwest track; or arc further westward, a path that could take it south of the islands. The disagreement is evident within the 1200 GMT Friday runs of the 20-member GFS ensemble (see Figure 3). As for intensity, Guillermo is likely to peak over the weekend, with NHC bringing the hurricane to low-end Category 3 strength (peak sustained winds of 115 mph) by Saturday. The unusually warm waters fostered by El Niño would keep Guillermo traveling over SSTs of at least 27°C (the rough threshold for sustaining a tropical cyclone) all the way to Hawaii. However, wind shear is expected to steadily increase as Giuillermo gains latitude and approaches the belt of upper-level westerlies noted above. Given its current track and intensity, and the increased climatological risk of hurricanes affecting Hawaii during El Niño, we will need to keep a close eye on Guillermo over the next few days. Twice-daily hurricane-hunter flights to monitor Guillermo have been slated beginning on Saturday, with the NOAA Gulfstream IV aircraft tentatively scheduled to sample the large-scale environment around Guillermo on Monday.

Figure 3. Projections for the track of Hurricane Guillermo produced on Friday morning by the 20-member GFS ensemble. The operational run is shown in white. Ensemble runs are produced by running the models at lower resolution than the operational run and varying the initial atmospheric conditions slightly to generate an "ensemble" of twenty potential weather situations, illustrating a range of possible outcomes.

Invest 94L shows little sign of strengthening
Invest 94L is still identifiable, but not very impressive, in the central North Atlantic. The loosely organized system was located around 12.5°N, 32.2°W at 8:00 am EDT Friday, moving west at about 15 mph. The circulation around 94L is highly elongated, with upper-level outflow evident but dry air invading the storm, leaving it with only weak shower and thunderstorm activity. The SHIPS statistical model brings 94L to moderate tropical-storm strength in the next several days, but none of the most reliable dynamical models for tropical cyclone formation indicate any substantial development of 94L, and NHC has lowered its five-day odds of development from 30% to 10%. Even if 94L managed to get a new lease on life in the central Atlantic, it would face largely hostile conditions as it continued west into the very high wind shear present across the Caribbean.

Figure 4. Infrared satellite image of Invest 94L (located at center left). Image credit: NOAA/NESDIS.

Soudelor a potential threat to Japan next week
Tropical Storm Soudelor should begin flexing its muscle over the next couple of days in the Northwest Pacific. Hindered over the last day by a tropical upper tropospheric trough (TUTT) to its north, Soudelor will soon escape the TUTT’s influence and likely launch into several days of significant strengthening. Soudelor’s peak winds were about 40 mph at 8:00 am EDT Friday, but the outlook issued by the Joint Typhoon Warning Center brings Soudelor’s winds to typhoon strength by Saturday and Category 4 strength (140 mph) by Monday. Track and intensity forecasts are increasingly uncertain beyond that point, as wind shear will be on the increase and water temperatures along Soudelor’s path will be cooler. It appears there is a good chance Soudelor will move far enough west to pose a potential threat to Japan later in the week.

Another off-season system pops up in the South Pacific
While our attention is focused on the peak season for tropical development in the Northern Hemisphere, Invest 91SH is defying seasonal expectations. The system was located at 7.8°S and 167.9°E at 8:00 am EDT Friday, moving slowly south-southeast with peak winds of around 23 mph. The 0600 GMT Friday run of the U.S. Navy’s version of the GFDN model brings Invest 91SH to tropical storm strength over the weekend before a weakening trend is projected to set in, well before the system approaches the islands of Vanuatu. A tropical storm in this basin in early August would be very unusual, as the official South Pacific season runs from November to April, but El Niño does tend to increase activity in the South Pacific. If 91SH does develop, it will be named Tuni and classified as the first South Pacific cyclone in the 2015-16 season. Another off-season system, Tropical Cyclone Raquel, formed at the end of June and intensified to Category 1 strength in early July, bringing at least one fatality and extensive damage to agriculture in the Solomon Islands. Raquel is the only tropical cyclone recorded to date in the South Pacific during July.

I’ll have another update by Monday at the latest. Wunderblogger Steve Gregory added a new post on Friday afternoon. We’re also pleased to welcome Dr. Phil Klotzbach (@philklotzbach) as a WU blogger. Phil worked with Dr. Bill Gray for many years on the Colorado State University seasonal hurricane forecasting project, and he is now lead author on those forecasts. In his first Weather Underground post, Phil weighs in on the multiple ways in which El Niño tends to inhibit Atlantic hurricanes.

Have a great weekend!


Pacific Northwest on Track for Warmest Summer on Record

By: Christopher C. Burt , 3:30AM,GMT on August 1,2015

Pacific Northwest on Track for Warmest Summer on Record

Another heat wave has engulfed much of the U.S. Pacific Northwest the past few days with Seattle, Washington now having observed eleven 90°+ temperatures so far this summer, an all-time record (9 such days in 1958 was the previous) and also July has been their warmest month ever observed. For some of the cities in the Northwest this has been the warmest June-July period ever measured and, barring a very cool August, will end up being the warmest climatological summer on record (June-August). Here are some details.

After enduring its warmest June on record Seattle has now endured its warmest July on record as well (see tables below for the figures). It also has been exceptionally dry with only .09” precipitation measured in July (normal is .66”) and .23” in June (normal is 1.43”). However, this is still no match for the June-July period of 1922 when only .03” accumulated! The July 2015 average temperature of 71.2° is also the city’s all-time (any month) heat record (previous 71.1° in August 1967).

Portland, Oregon is also on track for enduring its warmest summer on record following a record warm June and near-record warm July. In fact, July 30th was one of the hottest days on record for much of Oregon’s Willamette Valley. Corvallis Airport reached 108°, tying the town’s all-time (any month) record last set on August 10, 1981 at Corvallis State University (POR since 1889). Roseburg, further south, also reached 108°, just 1° shy of its all-time (any month) record of 109° set on July 20, 1946. Salem and Eugene both observed daily record highs of 105° (all-time records for both cities are 108° set on August 9, 1981) and Portland reached 103°, short of its record of 107° measured on three previous occasions. On July 31st The Dalles and Pendleton (in Oregon) hit 109°, the warmest temperatures measured so far during the current heat wave for first order stations. Neither are all-time records (111° on several occasions for The Dalles and 115° for Pendleton). Salem, Oregon has just experienced its warmest month on record (see table below). The coastal sites in northern Oregon and Washington have also been exceptionally mild. Quillayute, Washington has tied its warmest month on record with a 63.1° average temperature for July. (equal to such in August 2013).

In the tables below are sites in the Northwest that observed their all-time warmest June on record, how they fared in July, and what their combined June-July averages have been relative to their warmest climatological (June-August) summers on record. It would appear that Medford, Portland, and Salem in Oregon, as well as Seattle, Yakima, and Spokane in Washington are likely to end up with their warmest summers on record barring a very cool August. One aspect of this is that (should the heat trend continue) Yakima, Washington and Portland, Oregon will see back-to-back record warm summers. They just observed their hottest summer on record LAST summer in 2014!

New June monthly heat records (average temperature) for selected cities in the Pacific Northwest (top table), average monthly temperatures for July compared to record values for the same cities (middle table), and June-July average temperatures compared to warmest climatological summer (June-August) on record (bottom table).

Aside from the heat, drought conditions have significantly worsened across the region with 37% of the Pacific Northwest watershed now experiencing extreme drought conditions (a huge weekly jump from just 20% a week earlier).

Pacific Northwest Watershed drought monitor map for July 28th. Note how rapidly conditions have deteriorated in the past several months. Map from NOAA et al.

The hot weather and dry conditions have critically impacted the sockeye salmon runs along the Columbia River and its tributaries. Federal and state fishery biologists estimate that up to 80% of the salmon may perish since the fish become stressed at water temperatures above 68° and stop migrating when the water reaches 74° or higher. Many of the Columbian River tributaries are already measuring temperatures above 76°. The Columbian River itself is running at its lowest level for this time of the year in 60 years according to U.S. Fish and Wildlife Service officials.

The Columbia River is running at its lowest level in almost 60 years for this time of the year, threatening the annual sockeye salmon run. Photo from Freestock. com

Christopher C. Burt
Weather Historian

Tropical Cyclone Komen Soaking Waterlogged Bangladesh, Myanmar; At Least 39 Reported Dead

Nick Wiltgen
Published: July 30,2015

A slow-moving monsoon depression unleashed lethal amounts of rain in South Asia earlier this week prior to forming into a tropical cyclone over the northern Bay of Bengal Wednesday. The cyclonic storm named Komen reached tropical storm strength and moved inland Thursday. Since then, it has been downgraded to a depression over Bangladesh, however it still has the potential to further drench regions that are already reeling from flooding and mudslides. Gusty winds and rough seas are adding to the dangers, which in all have claimed at least 39 lives in two countries.
For about a week, heavy rainfall has been pounding southern parts of Bangladesh and parts of neighboring Myanmar thanks to a weak area of low pressure – designated a "depression" by meteorologists in that region – that formed over Bangladesh in association with the seasonal monsoon.

Extreme Rainfall
Even for a region where average July rainfall exceeds 600 millimeters (2 feet), the rains have been exceptional. The coastal city of Chittagong reported more than 800 millimeters (32 inches) of rain in just a three-day period July 24 through 26.
Much of southeastern Bangladesh has seen repeated heavy rainfall on a daily basis over the past week. The results have been deadly. Five people died in a landslide in Cox's Bazar Monday according to the Bangladesh-based Daily Star. Four others were pulled from the mud alive. Two other people drowned in flooding elsewhere in the town of 52,000 residents, the report said. Cox's Bazar has reported more than three feet of rain since July 24, exceeding its already high monthly average rainfall of 924.6 millimeters (36.40 inches) according to Bangladesh Meteorological Department climate data.
After the depression became Cyclone Komen, additional casualties were reported along the coast of Bangladesh Wednesday.
The Daily Star said a boat capsized in rough seas off Cox's Bazar Wednesday, killing two and leaving six missing. Falling trees were blamed for two deaths, and a boy died when a wall collapsed onto him. The cyclone was also blamed for the death of a newborn who succumbed to respiratory disease while being carried to a cyclone shelter by her parents.
While official rainfall totals are harder to come by in Myanmar, the effects have been as devastating or worse. At least 27 people are reported dead due to flooding in western and central parts of that country, according to a report from the BBC. Some 17,000 homes had been destroyed as of Monday from the days-long deluge, according to China's state-run Xinhua news agency.
According to The Irrawaddy, a news portal covering Myanmar, power is out in several impoverished townships in the western part of the country, and a local leader voiced concern the damage may be heavier than local resources can handle.

Current Enhanced Satellite
The monsoonal depression that spawned Komen moved offshore from Bangladesh before strengthening over the Bay of Bengal, but it soon reversed course and moved back toward shore. The Bangladesh Meteorological Department said the center of Komen made landfall along the coast of southeastern Bangladesh between Hatiya and Sandwip late Thursday afternoon local time. (Bangladesh is 10 hours ahead of U.S. Eastern Daylight Time.)
The lingering circulation could continue to bring torrential rainfall to the already-stricken region, which consists of low flood-prone coastal plains in southeast Bangladesh and a series of landslide-prone ridges from the interior of that area into western Myanmar. Bangladesh-based weather radars showed spiral bands of rain affecting southeastern Bangladesh during the day Friday.
The potential for flooding rainfall will also include parts of northeastern India. The India Meteorological Department has issued heavy rainfall warnings.

Rainfall Forecast
With several rivers already out of their banks, the additional rain will merely aggravate ongoing flooding.
Stay with The Weather Channel and as we continue to follow this dangerous situation in South and Southeast Asia.
MORE: Cyclone Viyaru (formerly Mahasen), Bangladesh, May 2013

California Is Missing a Year's Worth of Rain, Study Finds

Andrea Thompson,
Published: July 31,2015

California ?Rain Debt? Equal to Average Full Year of Precipitation
The amount of rain that California has missed out on since the beginning of its record-setting drought in 2012 is about the same amount it would see, on average, in a single year, a new study has concluded.
The study’s researchers pin the reason for the lack of rains, as others have, on the absence of the intense rainstorms ushered in by so-called atmospheric rivers, the ribbons of very moist air that can funnel water vapor from the tropics to California during its winter rainy season.
Overall, the study, accepted for publication in the Journal of Geophysical Research – Atmospheres, found that California experiences multi-year dry periods, like the current one, and then periods where rains can vary by 30 percent from year to year. Those wet and dry years typically cancel each other out.
(MORE: Study Finds Our Nation's Capital Is Sinking Into the Sea)
California’s accumulated precipitation debt from 2012 to 2014 shown as a percent change from the 17-year average using the TRMM mission’s multi-satellite observations.
(Goddard’s Scientific Visualization Studio)

The El Niño-Southern Oscillation, one phase of which has ushered in some of the state’s wettest years, only accounts for about 6 percent of overall precipitation variability, the researchers found.
Drought began creeping across the California landscape in 2012 and has continued to mushroom year after year as winter rains and snows were much diminished. The atmospheric rivers that normally funnel in moisture-laden air were thwarted by a persistent area of high pressure that blocked them from reaching California. This winter, precipitation that did manage to fall mostly did so as rains thanks to record-high temperatures linked to extremely warm waters off the coast, leaving the snowpack at record low levels.
The new study looked at satellite measurements of rainfall from NASA’s Tropical Rainfall Measuring Mission (TRMM) satellite, as well as a recreated climate record that used both observations and model data to gauge how much California’s annual precipitation varied and how much it was in the hole after four years of drought.
The researchers found that in an average year, the state sees about 20 inches of rain; it turns out that’s also about the amount of missing rain since 2012.
To dig out of the drought in just one winter, the state would have to see 200 percent of its normal yearly rain, to cover both that year’s rain and make up the missing amount.
That wet a winter isn’t very likely happen, Daniel Swain, a PhD student at Stanford University, said in an email. And if it did occur, it would mean major flooding, he added. Swain wasn’t involved with the new research.
The study also looked at another recent dry period, from 1986 to 1994, and found a 27.5-inch precipitation deficit over that period. While that was overall greater than the current drought, the per year rain deficit is much higher this time around, Swain pointed out.
(MORE: Heat Wave Threatens All-Time Records)
Added to that, “temperatures in CA during the current drought have been warmer than during any previous drought on record, which has greatly amplified the effect of the precipitation deficits,” and helped fuel the wildfires currently flaring up around the state, Swain said.
Many are hoping the current El Niño will make a serious dent in the drought, as it looks to become a strong event, and those are associated with higher odds of increased winter rains over at least parts of the state.
The study found that the whole El Niño-Southern Oscillation cycle only accounts for about 6 percent of the variation in yearly California precipitation. That cycle encompasses not just strong El Niños, but weak ones, as well as neutral and La Niña conditions, and when separated out “very strong events (like the El Niño currently underway) exert a far greater influence upon California climate than weak ones,” Swain said. So this year’s El Niño could play a major role in what precipitation California sees.
What’s important this year, Swain said, is where the precipitation falls and how much of it falls as snow to build back up the snowpack that keeps water flowing into reservoirs come the warm, dry days of summer.
You May Also Like:
  • Drought May Stunt Forests’ Ability to Capture Carbon
  • What Warming Means for 4 of Summer’s Worst Pests
  • Warming May Boost Wind Energy in Plains States
  • Fossil Fuels May Bring Major Changes to Carbon Dating
MORE: Shocking Images of California's Drought

Feels-Like Temp Reaches 163 Degrees in Iran; Days Off Ordered as Mideast Broils in Extreme Heat Wave

Nick Wiltgen
Published: July 31, 2015

Even in the Middle East, where scorching heat is part of everyday life during the summer, coping with extreme temperatures has its limits. A heat wave that has been building for days is testing those limits – and will test the region's national temperature records too.
The searing heat has led to an impromptu, mandatory four-day holiday in Iraq beginning this past Thursday.
The government has urged residents to stay out of the sun and drink plenty of water, but for many of the more than 3 million Iraqis displaced by violent conflict, that poses a dilemma.

Current Conditions: Iraq, Iran, Kuwait
Chronic electricity and water cuts in Iraq and other conflict-ridden countries make heat waves like the present one even more unbearable – particularly for the more than 14 million people displaced by violence across the region. In the southern Iraqi city of Basrah earlier this month, protesters clashed with police as they demonstrated for better power services, leaving one person dead.
Unlike other countries in the region, Iraq lacks beaches and travel restrictions make it difficult for people to escape the sweltering heat, leaving many - even those fortunate enough to live in their homes - with limited options for cooling off. Some swim in rivers and irrigation canals, while others spend these days in air-conditioned shopping malls.

Current Heat Index (Feels-Like Temperature)
To the south, in the similarly sweltering Persian Gulf region, residents cranked up their air conditioners, and elsewhere in the Middle East, those who could headed to the beach to escape Thursday's soaring temperatures, high even by the standards of the region.
Water temperatures in the Persian Gulf routinely warm into the 90s each summer, releasing massive amounts of water vapor into the air above. For those unlucky enough to catch a breeze from the Gulf, the humidity can be stifling.
On Thursday, those breezes blew toward the Iranian side of the Gulf. At 3:30 p.m. local time (1100 GMT) Thursday, the manned observation site at the Mahshahr Airport in southwest Iran reported a temperature of 109 degrees (43 degrees Celsius) and a dewpoint of 90 degrees (32 degrees Celsius). Using the American heat index formula, those figures yielded a mind-boggling feels-like temperature of 159 degrees (70 degrees Celsius).
It was even hotter on Friday at the Mahshahr Airport when temperatures reached 114.8 degrees at 4:30 pm local time with a dew point of 89.6 degrees, leading to a heat index value of an incredible 163 degrees (72.7 degrees Celsius).
It is not uncommon for well-off Gulf citizens to decamp with their luxury cars and servants to cooler spots such as Britain or Switzerland as temperatures rise. Saudi Arabia's King Salman, joined by a delegation numbering in the hundreds, is currently cooling off in the south of France, where high temperatures Thursday were in a comparatively mild range between 73 and 93 degrees (23 and 33 degrees Celsius).
Several Gulf states, including the United Arab Emirates, Qatar and Saudi Arabia, mandate midday breaks when temperatures are at their highest for low-paid migrant laborers during the summer months. But that only provides some relief as many still spend long hours working in the heat and travel to job sites on buses without air conditioning.

Three-Day Forecast
A Filipino migrant rights activist collapsed and later died of apparent heat stroke during a visit to his country's consulate in Dubai this week. Highs over the past week have hovered near 113 degrees (45 degrees Celsius) in Dubai, and the Dubai area has not reported a temperature below 90 degrees (32 degrees Celsius) even at night since July 24.
Another of the hottest spots in the Gulf was Kuwait City, where the official high Wednesday was 121.3 degrees (49.6 degrees Celsius). The civil aviation authority's meteorological department forecast daytime conditions as "very hot" and overnight temperatures as "relatively hot," with moderate winds providing little relief.
Kuwaitis nonetheless took it in stride.
Nazem al-Ghabra, 31, who works in corporate communications, told the Associated Press: "We're used to this weather, and Kuwait is well-equipped for this harsh weather as almost everything is indoors, even car parking."
While Kuwait may be well-equipped for heat, this episode promises to be among the more extreme in modern recordkeeping.
Climatologist Maximiliano Herrera says Kuwait's national all-time record high is 53.6 degrees Celsius (128.5 degrees Fahrenheit) set at Sulaibya on July 31, 2012. Preliminary data show a high of at least 52.8 degrees Celsius (127.0 degrees Fahrenheit) at Mitribah, Kuwait, on Thursday.
According to Herrera, the national heat records for both Iraq and Iran are both 53.0 degrees Celsius (127.4 degrees Fahrenheit) set in a heat wave at this time of year in 2011. (In Iran the record was tied in August 2014.)
The hottest temperature in Iraq on Thursday was in Kanaqin where it hit 52 degrees Celcius (125.6 degrees Fahrenheit). Baghdad wasn't far behind at 51 degrees Celcius (123.8 degrees Fahrenheit).
The World Meteorological Organization says the official record-high temperature for Asia, of which the Middle East is a part, is 129 degrees (54 degrees Celsius) set at Tivat Tsvi, Israel, on June 21, 1942. Herrera says this record is unreliable and lists the 2012 Kuwait record as Asia's record.
Information from the Associated Press was used in this report.
MORE: Iraqi Heat Wave, July 2015

Hurricane Guillermo Is Strengthening in Eastern Pacific

July 31,2015


  • Hurricane Guillermo was located about 1,570 miles east-southeast of Hilo, Hawaii, as of Friday morning.
  • Guillermo strengthened into a hurricane early Friday and additional strengthening is expected. Guillermo may become a major hurricane (Category 3 or higher) and there is a chance that Guillermo could undergo a period of rapid intensification.
  • For the next five days Guillermo is forecast to stay over open waters as it moves to the west-northwest in the general direction of Hawaii.
  • Early next week, Guillermo should encounter increasing upper-level winds and cooler waters which will lead to gradual weakening.
  • It's too early to speculate on whether this system will eventually have any impact on the Hawaiian Islands. IF there are any impacts, it would not be until the middle or late portion of next week.
  • Air Force Hurricane Hunters are tentatively scheduled to investigate this system on Sunday.
(MORE: Expert Analysis | Hurricane Central)

The Latest Status, Forecast Path and Infrared Satellite Maps

Storm Information

Projected Path
MORE: Amazing Hurricane Images (PHOTOS)

West Coast Heat Wave Clinches a Record Hot July in Seattle; Northeast Hot, But Not Historic

Chris Dolce
Published: July 31,2015

Summer heat is gripping opposite sides of the country into this weekend, including parts of the West and the Northeast.
The heat has helped to clinch one of the hottest Julys on record for some Northwest cities. It's also helped set a record for the most 90-degree days in a year in Seattle and has given Portland its hottest temperatures since 2009. After a hot weekend, some relief will finally arrive next week.
A substantial warm up is also occurring for places that saw snow earlier this week in Montana, Idaho and Wyoming.
The Northeast heat will not be as extreme, but it will stick around into next week for some cities.
Let's break down the forecast details on this summery weather pattern for both regions.

Northwest: Clinching a Record Hot July

Current Northwest Temperatures

Heat Alerts

A strong ridge of high pressure has built over the Northwest as the jet stream bulges northward to the Canadian border. This is allowing temperatures 5 to 20 degrees above average to take hold across parts of Oregon, Washington, Idaho and Montana this weekend
(MORE: Strange July Weather Pattern Brings Snow, Tornadoes)
It's a fitting end to one of the hottest Julys on record in parts of the Pacific Northwest. The following cities have clinched their hottest July on record (all data is preliminary and will be finalized August 1):
  • Seattle: July 2015 average monthly temperature is 71.2 degrees. This beats the old July record of 69.5 degrees set in 2009.  Depending on the final data, this may have also beat out August 1967 (71.1 degrees) for the hottest of any month on record. Records date back to 1894.
  • Eugene, Oregon: July 2015 average monthly temperature is 71.5 degrees. This beats the old July record of 71 degrees set in 1958. Records date back to 1912.
  • Salem, Oregon: July 2015 average monthly temperature is 73.1 degrees. This beats the old July record of 72.5 degrees set in 2014. Records date back to 1893.
Portland, Oregon, has seen consecutive days with 100-degree heat, topping out at 103 degrees on Thursday and 101 degrees on Friday. Thursday's 103 was the hottest temperature there since July 29, 2009. Those hot temperatures have likely vaulted Portland to its second hottest July on record with an average temperature of 73.9 degrees, falling just behind 1985 which had an average of 74.1 degrees. Temperatures in Portland will be in the middle to upper 90s this weekend.
Seattle saw its eleventh 90-degree day of 2015 on Friday, which is a new record for the most 90-degree days in a calendar year. The old record was nine days set in 1958. Seattle averages just two days with 90-degree heat annually. The Emerald City could add to this record with temperatures forecast to be near 90 this weekend. A heat advisory has been issued by the National Weather Service for the Pudget Sound area through Saturday.
Eugene and Salem, Oregon, both set daily record highs on Thursday by topping out at 105 degrees. This was one degree shy of an all-time July record high in Eugene. Another daily record high of 103 degrees was set in Eugene on Friday. Highs are expected to be in the low 100s on Saturday followed by middle 90s Sunday.

Forecast Highs

Forecast Highs

Farther south, Roseburg, Oregon, was one degree short of an all-time record high on Thursday when it topped out at 108 degrees. Friday's high was 107 degrees.
For parts of central and eastern Washington, this round of hot temperatures probably won't be quite as intense as the late-June record-breaking heat wave. Spokane hit 105 degrees in late-June, but should hold near 100 degrees through the weekend.
In Northern California, Redding topped out at 114 degrees on Thursday, which set a new record for the date. Sacramento (downtown) set a daily record high of 107 degrees on Wednesday.
Boise, Idaho, will just squeak past 100 degrees for the next few days. Idaho's capital should fall well short of its June 28 high of 110 degrees, which set an all-time record for June.
For parts of Montana, this is quite a change from the way the week started.  For example, Missoula, Montana, saw rain with temperatures in the upper 40s and 50s on Monday afternoon. The high was in the low 90 degrees there on Thursday and Friday. Even hotter readings in the middle to upper 90s are possible this weekend.
High elevation areas that saw snow on Monday in the northern Rockies will also see significant temperature rises. Big Sky, Montana, could be near 80 degrees this weekend and Grand Targhee, Wyoming which saw 1.5 inches of snow early this week will see highs in the mid 80s this weekend.

Northwest Heat Relief Ahead

Some heat relief will finally arrive early next week in the Northwest. The entire region will see temperatures trend back to early-August averages Monday-Wednesday as the upper-level ridge responsible for the hot weather shifts east.
Highs of 80-84 degrees are anticipated in Seattle during the first half of the new week. Portland will see temperatures in the middle 80s Monday and Tuesday, followed by low 80s Wednesday.
Upper 90s and low 100s will also be eliminated from parts of eastern Washington, eastern Oregon, Idaho and western Montana as the new week begins.

Northeast: Heat Wave Possible in Some Cities

Forecast Highs

Wednesday was the hottest day so far in 2015 in New York City (96 degrees) and Albany, New York (95 degrees). Concord, New Hampshire, set a daily record high of 96 degrees, beating the old record for July 29 of 95 degrees set in 1949.
Highs will stay a handful of degrees above average for mainly eastern sections of the region into early next week.
For the most part, this heat in the Northeast will not be record breaking. However, the longevity of it will likely be greater than we've seen so far this summer in some cities. By early next week, some locations could meet the definition for a heat wave in the Northeast, which is generally defined in that region as three or more days in a row with temperatures at or above 90 degrees.
(MORE: Daily Forecast Maps)
That said, there is a big difference between the way it felt Thursday and the way it will feel into the weekend across the Northeast. This is because much drier air has filtered in behind a cold front that brought strong thunderstorms to the region on Thursday.
As a result, the humidity that has added to the discomfort dropped significantly, making the heat more bearable. For example, Washington, D.C. had an actual high of 92 degrees with a peak heat index of 103 degrees on Thursday. Friday's high was just as warm, but with lower humidity the heat index was not a factor.
New York City is likely to see highs mainly in the low 90s or upper 80s into early next week. So far this year, the Big Apple has experienced six days with 90-degree heat. Highs in the 90s were recorded on back-to-back days for just the second time this year on Tuesday and Wednesday.
Farther south, the Mid-Atlantic will sizzle through highs in the low to middle 90s into next week, including Washington, D.C.Baltimore and Philadelphia.
Washington, D.C. has already seen its fair share of 90s in 2015, with 33 days total through Friday. They will likely meet or exceed their annual average number of 90-degree days in the next few days which is 36.

MORE: Northern Rockies See July Snow

Hurricane Guillermo Spinning West in the Eastern Pacific; Hawaii Impacts Possible

July 31,2015


  • Hurricane Guillermo was located about 1,335 miles east-southeast of Hilo, Hawaii, as of Friday evening.
  • Guillermo underwent rapid intensification (defined as at least a 35 mph increase in maximum winds in 24 hours) Thursday into Friday and currently has top sustained winds of 105 mph, making it a Category 2 hurricane.
  • For the next few days Guillermo is forecast to stay over open waters as it moves to the west-northwest in the general direction of Hawaii.
  • Early next week, Guillermo should encounter increasing upper-level winds and cooler waters which will lead to gradual weakening back to a tropical storm by the time it reaches the general area of Hawaii.
  • It's too early to speculate on whether this system will eventually have any significant impact on the Hawaiian Islands. IF there are any impacts, it would not be until the middle or late portion of next week.
  • Air Force Hurricane Hunters are tentatively scheduled to investigate this system on Sunday.
(MORE: Expert Analysis | Hurricane Central)

The Latest Status, Forecast Path and Infrared Satellite Maps

Storm Information

Projected Path
MORE: Amazing Hurricane Images (PHOTOS)

Warmup in UK Follows Cool Week

July 31,2015; 11:02PM,EDT
Warming will spread over much of the United Kingdom Sunday and Monday, following a string of rather cool days.
England, especially, will be feeling warm with many highs of 23-25 C on Sunday, then 25-27 C on Monday. The warmest areas will include the Midlands as well as the East and South of England.

In the meantime, the high temperature in the United Kingdom will be no higher than normal on Saturday. London, for instance, will reach a high of 21 C on Saturday, just shy of the normal 22 C for this time of the year.
While London will experience near-normal temperatures, a trough moving through Scotland will supply showers and chilly air to much of the rest of the United Kingdom.
This trough will depart to the northeast by Sunday setting the stage for warmer air to return.
United Kingdom Weather Center
Detailed London Forecast
Check AccuWeather MinuteCast® for London

The primary trigger for the warming trend will be an unusually strong storm system that will spin at sea west of Ireland on Sunday and Monday. Southerly winds ahead this storm and its cold front will draw warmth into England. However, truly hot air will stay on the continent, flowing across Spain and France into Germany by Monday afternoon.
The Atlantic storm will usher cooler, showery weather eastward in the United Kingdom later Monday and Tuesday.
Meteorologist Eric Leister contributed to this story.