Hazardous Weather Blog

Where is El Niño?

There has been a lot of talk recently about the potential for an upcoming El Niño this fall/winter. Why has the atmospheric response been seemingly delayed relative to the gradual warming of the eastern Pacific waters? For more: NOAA ENSO Blog

TS Arthur Threatens U.S. East Coast

The first tropical storm and soon-to-be hurricane is threatening to affect the U.S. East Coast on this 4th of July Weekend. The circulation TS Arthur is gradually intensifying, and its structure of convection is becoming more symmetric. The time at which it crosses the hurricane intensity threshold has accelerated. For more, please read the summary of expected impacts as outlined by the The Washington Post’s Capital Weather Gang.


First Atlantic Hurricane of 2013

After a late start, the first hurricane of the 2013 Atlantic Hurricane Season has formed. Thankfully, Hurricane Humberto is far away from land and is not expected to affect the United States at this time. For more about the current tropical cyclone activity in the Atlantic, please read Dr. Brian McNoldy’s recent blog article.

All Quiet in the Atlantic... (For Now)

As we continue to approach the climatological peak of the Atlantic hurricane season, all appears to be quiet for now. This synopsis by Dr. Brian McNoldy a little less than a week ago still holds, and the global numerical weather prediction models (e.g., GFS, ECMWF, UKMET, NAVGEM) still show little sign of any tropical cyclogenesis in the coming days and into early next week. The tropical Atlantic has recently felt the effects of dry, dusty Saharan air blowing in from Africa, which has helped to suppress tropical cyclone activity. This is expected to continue in the coming days.

nasa_2013080800_dustex_atlSource: WeatherBELL

However, now is not the time to let your guard down! There is still much more to the Atlantic hurricane season, and now would be a great time to review your hurricane preparedness plans, particularly for our friends on the East and Gulf Goasts! Also, please take a moment to read Dr. McNoldy’s “cone refresher” to review the meaning of the National Hurricane Center’s forecast track product. This UntamedSkies.com “Hazardous Weather Blog” is intended for a wide audience interested in all weather hazards, so for Atlantic-specific tropical cyclone updates, please stay tuned to Dr. McNoldy’s “Tropical Atlantic Update,” which is a source of reliable blog posts about current activity in the Atlantic.

Yarnell Hill Wildfire Tragedy


For the past week, the western United States has been faced with a searing heat wave, with temperatures soaring well over 100°F and even over 120°F in spots. This is thanks to a stubborn ridge of high pressure, seen in the figure below as a crest in the 500 hPa (mid-troposphere) wave pattern that is “stuck” over the western portion of the continent. This is in contrast to the eastern half of the U.S. that has been experiencing below-average temperatures.


Along with the oppressive heat, lightning associated with dry thunderstorms have ignited numerous wildfires throughout the region. Extremely dry, windy, and hot conditions have fueled the wildfires and posed a significant challenge to the wildland firefighters who are on the front lines.

This past Sunday, June 30, the Granite Mountain Hotshots, an elite team of 20 wildland firefighters, lost 19 of their members in a severe tragedy in the Yarnell Hill Wildfire. This now ranks as the worst wildland firefighting tragedy since 1933 and is the deadliest firefighting event since 9/11. At the time of this writing, the fire has burned 8,400 acres and is still only 8% contained.

The investigation into what happened is only now beginning, so the details of the firefighters’ last moments are not yet clear. However, what we do know is that the fire shifted direction rapidly and caused the firefighters to deploy their fire shelters, which proved to be no match for the blaze. According to this report from AZCentral:

…winds from the southwest were gusting at 15 to 25 mph at 4:01 p.m. at the monitoring station near the blaze. An hour later, winds were gusting at 30 to 47 mph from the northeast.

According to the Weather Underground archives of MQSTA3 RAWS station records from near the fire, we see that a dramatic wind shift occurred near 5 pm on Sunday, June 30, roughly corresponding to when the firefighters were believed to have deployed their fire shelters.


This dramatic near-180° wind shift from the south-southwest to the north-northeast was accompanied by a wind gust over 40 mph, leaving the firefighters with little time to respond, particularly with their position in a valley between two ridges.

So what was the source of this sudden wind shift?

Despite what may have been initially reported, this was not a serendipitous or random occurrence. A look through archived data from the KFSX radar showed that in the 1.5 hours leading up to the tragedy, numerous thunderstorms were present to the northeast of the fire. Furthermore, many of the storms that dissipated left behind numerous outflow boundaries (fine, light blue lines in the radar image), suggesting the presence of stronger gust fronts that day. An outflow boundary was not detected by the radar near the Yarnell Hill fire most likely because the radar beam that is oriented at 0.5° above the horizon was sampling higher up in the atmosphere by the time it reached that location. However, given the presence of outflow boundaries near most of the showers and thunderstorms around Flagstaff, it would be reasonable to assume that similar features were present ahead of the storms in Yavapai County. The weak radar reflectivities that remained semi-stationary to the southwest of Prescott may have been associated with the fire.


The rapidly decreasing radar reflectivities suggested that the Yavapai County storms were quickly dissipating as they passed Prescott, during the stage of a thunderstorm’s life cycle when downdrafts are likely to be particularly strong. These storms were also clearly evident in GOES-15 visible satellite imagery, as seen here in an animation generated by Dr. Dan Lindsey at NOAA. The red X marks the approximate location of the fire. A more technical discussion of satellite observations is available from the CIMSS Satellite Blog.

This dramatic, time-lapse video was filmed from Congress, AZ, looking toward the northeast at the fire. Toward the end of the video, note the rapid shift of the fire as the gust front passed, which resulted in jumping flames and smoke being blown toward the camera.

So what caused the greater prevalence of these intense downdrafts and associated gust fronts? The 0000 UTC (6 pm MDT) weather balloon sounding from Flagstaff depicted a dry layer of low-level air above the ground, sitting underneath a moist, mid-level layer. The red line shows the vertical temperature profile, and the green line shows the vertical dewpoint temperature profile. Where the lines are closer together indicates more saturated or relatively “humid” air, whereas the lines farther apart indicates drier air.


A similar pattern was evident in the sounding from Tuscon at the same time, with the low-level air being even drier (even greater separation between the red and green lines). This suggested that conditions were favorable for mid-level precipitation falling through the sky to evaporatively cool and accelerate toward the ground and spread out, resulting in particularly strong gust fronts ahead of the thunderstorms that day in Arizona.


Remarkably, the mesoscale evolution and associated wind gusts of these storms were well predicted by numerical models. For example, the NOAA High-Resolution Rapid Refresh model run at 1900 UTC 30 June accurately predicted the wind gusts that would be associated with the thunderstorms approaching the Yarnell Hill Wildfire… four hours in advance! Still images of numerical model output are discussed further in Dr. Cliff Mass’s blog, but the bottom line is that mesoscale numerical models were indeed able to capture gust front dynamics near the wildfire that day.

Although hindsight is always 20/20, it would be wise to consider what could have been done to prevent this tragedy, given that the meteorology was no surprise. Perhaps the results of the investigation should lead to a discussion of how and to what capacity meteorologists can facilitate the decision-making process among fire response teams. When requested by incident commanders, the National Weather Service deploys Incident Meteorologists (IMETs) into the field to help with fire weather forecasting, but one was not present during the fire on June 30 because it was still relatively small and not yet classified as a “Type 1 Incident.” Spot forecasts were provided by the National Weather Service on June 30, but they were not enough to prevent the tragedy. An IMET was not deployed until the following day, yet it would be unrealistic to expect any greater coverage of IMETs for small incidents. So as the formal investigation continues, and given all this advance meteorological evidence of a tragedy in the making, we should ask:

What else can be done to bridge the gap between the science and the decisions?

On a more personal note, although I have never met any of the 19 fallen firefighters, I have friends who were recent wildland firefighters and who have shared with me their passion for being on the fireline. Two months ago, when I taught a FEMA course at the National Emergency Training Center, collocated with the National Fire Academy, I shared the hallways, courtyards, and dining hall with wildland firefighters, whose energy and passion for service were tangible. These individuals are young, energetic teammates who must endure long hours of service in the toughest conditions, but who most likely could not imagine doing anything else. That passion is not unlike the fascination that myself and my fellow meteorologists have when we pursue the most severe storms to improve our understanding of them for the sake of public safety. To the fallen members of the Granite Mountain Hotshots, to their lone survivor, and to all of their family and friends, I offer my most heartfelt condolences. Their sense of service is an inspiration to us all and will live on in our hearts and minds.

For the latest updates on the ongoing investigation of this tragedy, please refer to this website: www.YarnellFallenFireFighters.com.

Update 7/18/13: Initial report about the Yarnell Hill Fire resources deployment, released by the Arizona State Forestry Division on 15 July 2013. Download PDF


Welcome to the re-launch of UntamedSkies.com! This new and improved website now includes multimedia and interactive features, such as the Incident Map Room and this Hazardous Weather Blog. This re-launch comes within one month of the devastating EF-5 tornado that tore through Moore, Oklahoma on May 20, 2013, which killed 24 people and injured hundreds more. This event was followed by another EF-5 tornado near El Reno, Oklahoma among a cluster of severe storms on May 31, 2013 that caused several other tornadoes and flash flooding, all of which killed 22 people, including the well-respected scientists and storm chasers, Tim Samaras, his son Paul, and Carl Young.

Just today, the NOAA National Climatic Data Center announced that in the year 2012, extreme weather and climate events caused over $110 billion in damage, consisting of 11 disasters that cost over $1 billion each, including Hurricane Sandy and the central U.S. drought and associated wildfires. Since records began in 1980, the year 2012 ranks as the second-costliest year to 2005 and as the year with the second-most number of billion-dollar events, behind 2011.

It is clear that hazardous weather has become an increasing issue of concern for the safety and security of the citizens of the United States, where approximately 640 fatalities per year (based on a 10-yr average) and an economic cost of $485 billion per year are blamed on the weather. Hazardous weather events also occupy a significant portion of the national and local media attention, and a day does not go by without weather being discussed among the general population via social media. While all this attention to weather issues may raise awareness and inspire people to seek further education about weather preparedness and safety, the flurry of online information can make it difficult for those outside of the meteorology community to distinguish between reliable and unreliable sources.

This “Hazardous Weather Blog” will collect and interpret the latest news articles, weather data, research papers, and other noteworthy blogs in concise entries so that decision makers, emergency managers, first responders, and concerned citizens can get the facts about hazardous weather events while also learning about the most important developments in the field of meteorology. The content of this blog is not meant to cover all hazardous weather events in real-time. Rather, the periodic entries will be limited to high-impact and important events that would be of interest to a wide audience, with the purpose of bringing together the meteorology and decision-making communities. Important issues concerning the intersections of the four Mission Areas of UntamedSkies.com (scientific research, weather forecasting, management & training, and public policy) will be featured as well. Entries will be categorized by hazard type and/or the four Mission Areas.

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