25th Anniversary of the March 13, 1990 Tornado Outbreak

March 13, 2015 marks the 25th anniversary of the tornado outbreak that spawned 59 tornadoes across Iowa, Kansas, Missouri, Nebraska, Oklahoma and Texas. The largest and most destructive tornado was the F5 tornado that demolished Hesston, Kansas. A more detailed write-up is available from our colleagues at the National Weather Service Office in Wichita, Kansas: http://www.crh.noaa.gov/ict/?n=hesston
In Iowa, multiple severe thunderstorms swept across the state and produced 14 tornadoes, large hail to the size of golf balls, and wind gusts as high as 75 mph. The most destructive tornado in Iowa was an F4 that struck Prairieburg in northeast Linn County and was on the ground for 19 miles into Jones and Delaware Counties. An F2 hit Ankeny, injuring 15 people and producing 6 million dollars in damage. The largest hail reports were near Elvira and 75 mph wind gusts caused damage near Little Sioux and Logan. This was part of a wild stretch of weather in early to middle March of 1990 that saw a significant ice storm followed by several severe weather and tornado outbreaks then a big snow storm, all in a nine day stretch.

Here’s another great write-up on the March 13, 1990 tornado outbreak from the NWS Office in Hastings, Nebraska: http://www.crh.noaa.gov/gid/?n=march13,1990tornadoes

Fire Weather Updates

Post by Frank Boksa – Journey Forecaster

Fire Weather Season is upon us and a new product will be introduced this year.  I would like to take a moment to remind everyone of the products we have to keep you informed and safe. Our daily fire weather forecast product is the Fire Weather Planning Forecast. This product is issued daily by 6 AM from March 1 through November 15. During peak spring (March 1 through June 1) and fall (September 1 through November 15) seasons this product is issued twice daily by 6 AM and 4 PM. This product is intended for decision support to those responsible for planning prescribed burns and to the general public who plans a legal burn on their property.

The Fire Weather Watch is a public product that the National Weather Service issues. It is not a routine product but whenever our forecasters have a high level of confidence that weather and fuel conditions combine to create a risk of fire danger and rapid fire growth, we will issue this product from 24 to 48 hours in advance of the threat. This product is typically followed by a Red Flag Warning. The criteria we look at is sustained wind speeds at or above 25 mph along with a relative humidity of 25 percent or less and if fuels (grasses and tinder) are sufficiently dry that they will quickly catch fire and/or allow for a fire to spread quickly. In general if a watch is in place, people planning a burn should consider alternative dates.

The Red Flag Warning is a public fire weather warning product that the National Weather Service issues whenever our forecasters expect wind speeds at or above 25 mph in combination with a relative humidity of 25 percent or less and dry fuels within the next 24 hours. This product is a warning to people that it is dangerous to burn and burning is not recommended. During a Red Flag Warning event, decision makers in the fire weather community as well as state and county officials may want to consider burn bans or to begin contingency planning for additional staff to handle fires that could quickly get out of control.

For marginal fire weather conditions the National Weather Service may issue a Special Weather Statement. The intent of this product is to convey to the general public that there is a concern for fire danger and that they should remain alert for possible upgrades to a red flag warning.

New for this year will be a map of Iowa on our website that will display the Grassland Fire Danger Index for all 99 counties in Iowa. The Grassland Fire Danger Index or GFDI map will serve as a quick glance advisory for all to be aware of what the fire danger is for all counties in the state of Iowa. Our goal with this product is to reduce the number of uncontrollable outdoor fires by alerting the public when conditions favor an extreme fire potential. This should not be used as the only tool to become informed of fire danger but it is very useful as a first step. The map of Grassland Fire Danger Index is an indication of rural fire potential throughout the state and will contain five ratings: low, medium, high, very high and extreme. National Weather Service offices serving Iowa will issue a Red Flag Warning for an area exceeding several counties wide where extreme conditions exist as fires are more likely to occur on those days and more likely to grow in size. While the Fire Danger Index does not predict how a fire will behave, it will give an indication of overall fire activity. Please take a look at this map and tell us what you think of it.


We will also run our safety videos on the fire weather page of our website so please check those out as well. For information on the 2013 Annual Operating Plan and to view forecasts and fire weather planning tools, please visit the National Weather Service website at: http://www.crh.noaa.gov/dmx/firewx.php

Training…So Much Training!

Post by Allan Curtis – Meteorologist Intern

DLOCEver wonder what sort of training meteorologists in the National Weather Service (NWS) go through during their first couple of years? Well, the short answer is a plethora. The amount and type of training can vary a bit depending on the office and area of the country. One piece of training I attended recently, and every meteorologist must go through, is called the Distance Learning Operations Course (DLOC). DLOC is typically attended within the first 12-18 months after being hired by the National Weather Service and is probably the bellwether piece of training provided by the NWS.

The name itself does not give much of an explanation for what it is. So what is DLOC then? It is a crash course in Dual Polarization Radar including its history and predecessors, its nuts and bolts, conceptual models, the algorithms used to create radar products and how to interpret and utilize them during severe weather warning scenarios. And that is just the short explanation. The course covers applications that can be used year-round, including winter weather, but really concentrates heavily on convective weather. One of the primary goals of the course is to prepare meteorologists to issue severe weather warnings, such as severe thunderstorm, tornado, flash flood warnings, and more. In all, the 2014-2015 course included 80 online modules, three instructor led webinars (equaling the “distance” part in the course name), and lastly, a full week at the National Weather Center in Norman, OK for additional classroom sessions and real-time case studies.

All of the online modules and webinars built up a knowledge-base, some of which was new and some was a refresher from college, to be applied, not just during the week in Norman, but throughout one’s career as a meteorologist in the NWS. The week of on-site training was really where headway was made in terms of determining whether or not you knew the material, were able to apply it, and helped highlight areas to be worked on and polished in the future. Certainly no one exited DLOC a bona-fide expert, but it provided a rock solid base and highlighted areas for growth. A typical day during the on-site training included a morning classroom session that highlighted a special topic, such as tornado forecasting or flash flooding, and a related afternoon lab session that allowed direct application of knowledge and simulated weather events from real cases across the country. The lab sessions then consisted of teams of three working together to analyze and issue any and all necessary warnings for a given event. The events were run in real-time in order to simulated the actual severe weather event itself. The simulations were supervised by instructors and they answered questions, provided insight, and pointed out nuances throughout the event. The lab sessions were able to drive home the importance of application of knowledge, time management, team work, and communication, of which would be impossible if strictly done at a distance like the online modules and webinars.

Generally, any degree bearing meteorologist can identify a severe thunderstorm or tornado worthy of a warning for a picturesque thunderstorm on the plains of Texas through Nebraska, but what about lines of storms or clusters of storms? Such as in the Washington D.C. area? Or the Columbia River Valley in Washington state? Or even in the desert areas of Nevada and Arizona? The instructors were cognizant of the text book situations often found on the plains, and were instead eager to provide cases that were not as clear cut and required a more thorough analysis and solid knowledge base. At the end of the week, the result was a worn out group of attendees that gained a better appreciation for what goes into making a warning decision and an understanding that most situations are not clear cut. Another result of the on-site training that is often overlooked and under-appreciated was the networking that began at the course that will ultimately result in colleagues and friends to fall back on for knowledge and support throughout a career.



Scout Day at NWS Des Moines

Post by Frank Boksa – Journey Forecaster

We had a record 111 scouts, leaders and parents attend this past Boy Scout Weather Merit Badge Day, which was held at the NWS Des Moines office on February 28. This program was started five years ago and for the last two years, we have had to add two more sessions, bringing the total from four sessions per day to six sessions per day. The course is designed to run through the weather merit badge requirements, talk about careers within the National Weather Service and in the field of meteorology, and provide guidance in the scout’s research assignments. The course does have a quiz at the end which the boys must pass in order to be signed off on the requirements covered in the session.

IMG_0180Forecaster Kenny Podrazik explains severe weather operations to the Boy Scouts.

IMG_0170Meteorologist Intern Kevin Skow (not pictured), discusses thunderstorm development.

IMG_0173Forecaster Frank Boksa covers the different types of careers in meteorology.

IMG_0183Senior Forecaster Brad Small answers some very challenging questions from the Scouts.

Spring-Summer Outlook 2015

Post by Miles Schumacher – Senior Forecaster

The winter of 2014-15 temperatures averaged very close to normal. With December and January both averaging warmer than normal, February was much colder than normal. Temperatures in the Pacific Ocean were in large part responsible for the late season cold.

The state of temperatures of the equatorial Pacific Ocean exhibited a weak El Niño temperature distribution. During the early winter, the warmest water, relative to normal, was located more over the east Pacific. The warmest water, relative to normal, has shifted into the central Pacific during the past few months. The typical expectation for an El Niño winter is for warmer than normal winters over the Rockies and Plains, cooler than normal over the southeast U.S. When the warmest water shifts west into the central Pacific, as it has this winter, the pattern shifts west with the cooler than normal weather extending over the eastern U.S. into the Plains. That occurred as the transition into the central Pacific took place during the last half of January and February. Another factor affecting the winter pattern was the pool of warm water from the Gulf of Alaska, extending south along the west coast. The warm waters favored the development of an upper level ridge of high pressure. That ridge also aided in the delivery of cold air into the U.S.

The circled area in figure 1 shows the overall warmer than normal temperatures along the equatorial Pacific, especially in the central Pacific. Little additional warming is expected, though above normal water temperatures are likely to remain this summer. The warm pool of water from the Gulf of Alaska south along the west coast is expected to cool slowly over the next several months.


Figure 1: Global sea surface temperature departure from normal.

The atmosphere typically follows a three to seven year cycle between El Niño and La Niña. Depending on the phase of the Pacific Decadal Oscillation (PDO), El Niño/La Niña is favored during warm/cold phase of the PDO. The Pacific is currently in the cold phase of PDO. La Niña conditions are favored by a two to one margin during the cold phase. The reason for that change is that during the warm phase of PDO, El Niño typically lasts 10 to 12 months. In contrast, during the warm phase of PDO, it will persist for 20 to 22 months. The development of El Niño was favored by many of the world models for this winter going into the summer. During the past six months, the PDO has exhibited a warm PDO signal. Indications are that the weak El Niño pattern may persist into next winter. Below is a set of forecasts of equatorial Pacific temperature departures from the Japan Agency for Marine-Earth Science and Equatorial Technology (JAMSTEC), see figure 2. Note that most model runs indicate above normal sea surface temperature (SST) is expected to remain through the next two years with significant cooling not taking place until later next winter. For SST departures to be considered either an El Niño or La Niño, the average temperature departure must be at least 0.5°C above or below normal, respectively, or more for three consecutive 90 day seasons.

Figure 2: Sea Surface temperature departure for the past year plotted in blue.  The forecasts for the next two years follow.  The red line indicates the mean of the nine forecasts made through January 2017.  The gray lines are the individual model runs.  Departure in degrees C is shown on the ordinate, with time on the abscissa.

Figure 2: Sea surface temperature departure for the past year plotted in blue. The forecasts for the next two years follow. The red line indicates the mean of the nine forecasts made through January 2017. The gray lines are the individual model runs. Departure in degrees C is shown on the ordinate, with time on the abscissa.

Although in meteorology no two years are the same strictly speaking, one can look at weather patterns of the recent past to give some indications of near term weather trends in the future. This forecast is based in large part on the best fit from several of the years that were the most similar to late last fall and the winter season just past. Considerations were also made for the state of the Pacific and the expected change to an El Niño state as well as the warm pool off the west coast and other factors that influence the weather pattern.

The Pacific SSTs are yielding a signal for the upcoming spring and summer months. The cooling effect brought on by the warm pool off the west coast, as well as the position of the El Niño warm pool, has become quite evident during the last winter. This is likely to persist into the spring. March is likely to be the coldest month relative to normal with temperature returning to normal or a little above for April and May. Other factors to consider are the development of drought areas. The southern U.S. drought and developing dry conditions over the north central states can affect temperatures, especially during the late spring and summer months. The near record extend of ice on the Great Lakes can be a factor, contributing to shunting Gulf moisture to the south as dry high pressure will be favored over the cold water.

For this spring, it is likely that the effects that have been seen this winter will persist for at least the first month to month and a half. Overall, temperatures will likely be a little cooler than normal. The trend for less than normal precipitation is expected to continue, though extremely dry conditions are not expected. See figure 3.

Figure 3: Mean Temperature (left) and Precipitation (right) departure for March of 2015 through May of 2015.

Figure 3a: Mean temperature departure for March of 2015 through May of 2015.


Figure 3b: Mean precipitation departure for March of 2015 through May 2015.

Looking ahead toward the summer for what is most typical of the El Niño patterns observed is that temperatures are not extreme. The summer temperatures over Iowa are likely to be warmer than normal. Though warmer than normal, it appears very unlikely that Iowa will see a return to the heat experienced in 2012 and 2013. Rainfall is expected to be a little below normal, but once again not by a great deal. It is unlikely that there will be a return to the extremely dry conditions of the summers of 2012 and 2013. Development of dry soil conditions, such as are currently present north and south of Iowa, need to be monitored for potential expansion. That change could result in less rainfall than is currently expected. See figure 4 for details.

It will be important to monitor the oceanic and atmospheric patterns over the next several months. Although the signs point more toward a warmer and drier summer than normal, at this time extreme conditions are quite unlikely.

These outlooks are based more heavily on statistics than many of the methods used by the Climate Prediction Center. The complete set of official forecasts from the Climate Prediction Center can be found on our website.

Figure 4a: Mean temperature departure forecast for June of 2015 through August of 2015.Figure 4a: Mean temperature departure forecast for June of 2015 through August of 2015.

Figure 4a: Mean precipitation departure forecast for June of 2015 through August of 2015.Figure 4a: Mean precipitation departure forecast for June of 2015 through August of 2015.

NWS Des Moines Hosts Decision Support Services Partner Seminar

Post by Mindy Beerends – Journey Forecaster

NWS Des Moines hosted several Decision Support Services Partner Seminars this past November to January. The seminars were for core partners located in central Iowa including local officials from area schools, healthcare, public works, the Iowa Department of Transportation and the Iowa State Patrol. The workshop focused on strengthening our partnerships and further discussing how to better work together during hazardous weather situations.

Decision Support Services (DSS) consist of the NWS Des Moines becoming part of a team of decision makers and providing concise interpretation of weather data in a fast, reliable and accurate manner to the core partners such as these local officials. The primary goal of DSS is to provide focused support to decision makers for significant hazardous weather events.

Communication is an integral part of being prepared and mitigating effects of significant hazardous weather. Therefore the seminars focused on communication and services discussing current DSS activities here at the office and highlighted the ways for our core partners to access information. Included in the seminars were discussions with, and feedback from the local officials on how our office can best serve their informational needs regarding significant hazardous weather situations. These exchanges were beneficial for both sides as the officials found new ways to access important weather information needed for their operations and the NWS learned of what types of weather scenarios most impacted each entity.

As the National Weather Service and the NWS Des Moines office continue to grow the DSS program, learning about the hazards that impact our core partners and being able to help them plan and prepare for these scenarios is one of the keys to successful disaster mitigation and helps build a Weather-Ready Nation!

DSS Seminar

DSS Seminar2