Tornado Warnings: The Map
One of the most frequently asked maps is for all plot of all the tornado warnings. Here are the tornado warnings issued by year. Each warning was color-filled red with an alpha value of 0.1. Thus, it would take 10 overlaps for the color to display as true red. Thus, the colors are shaded from light pink (no overlaps) to red (at least 10 overlaps). 1 October 2007 the tornado warnings transitioned from county-based warnings to storm-based warnings.
As you can see, the number of warnings increased up through the start of storm-based warnings. After that time period, the number of warnings increased, but the overlap has decreased. One thing that is very apparent is that the number of warnings across the southeast United States has certainly been on the increase…
Also, one visual aspect that should be more disturbing that it is, notice the number of county borders that stand-out in the storm-based warning maps of 2008-2010.
Weather Ready Nation: Tornado Warnings by CWAs
Tonight’s blog post depicts the number of tornado warnings issued by year by CWA. I should add a disclaimer: I am using the current CWA boundaries for all prior years. Thus, it one runs the risk of making incorrect assessments if one directly compares the specific increase in CWA tornado warnings counts. Instead, the idea is to look at the general trend in the number of warnings issued by forecast offices.
Data for 2007 and later years need to be understood in the context that WFOs have switched from county-based warnings to storm-based warnings. Thus, it is possible to have situations where multiple storm-based warnings are in effect when in the past a single county-based warning would have been issued. The flip side to that is, a single storm-based polygon can now capture 2 or more counties, which would have required multiple county-based warnings in the old system.
As I mentioned last night, the number of warnings issued can be thought of as a cumulative measure of the number of times the NOAA Weather Radios would have sounded in a specific CWA. Thus, the increasing number of warnings issued can be thought of in terms of the National Weather Service requesting more responses from the residents in their CWAs.
Tornado Emergencies Sans 2011
Probably the most often asked question of the last 24 hours has been, “Can you redo the WFO counts without including 2011?” So, here are the WFO counts sans 2011. The top three have changed slightly
- BMX (Birmingham, AL)
- MEG (Memphis, TN)
- JAN (Jackson, MS)
There were 83 tornado emergencies between 1999 and the end of 2010…
More graphics to come…
Data Mining Tornado Emergencies
Last night I posted a call for help from fellow meteorologists and weather nerds to help me acquire the tornado emergencies that I was missing. Wow! Thanks to the help of Jason Kaiser, Daryl Herzmann from Iowa State, and Rick Smith from National Weather Service (NWS) forecast office Norman, I now believe I have all tornado emergencies in my possession! Now the fun part of analyzing them begins! Since many people are already aware of my project, I decided to go ahead and post two quick graphics that I think will be of interest.
First, a bit about my method. For this analysis I treat the tornado warning and all subsequent severe weather statements associated with the tornado warning as a single episode. Since a tornado emergency can be issued in the text of either a tornado warning or a severe weather statement, all tornado emergencies issued within a single episode is consider a single tornado emergency. Consider the following scenarios:
Scenario 1: A tornado warning is issued for 2 counties and does not contain the tornado emergency text. Subsequently 4 severe weather statements are issued. The second severe weather statement contains the tornado emergency language for county A but not county B. The fourth severe weather statement contains the tornado emergency for county B but not county A. How many tornado emergencies will this count as?
Using my definition, even though 2 tornado emergencies were technically issued, they are both contained within a single tornado warning and thus this is treated as a single tornado emergency.
Scenario 2: A tornado warning is issued for county A and does not contain the tornado emergency text. Subsequently 2 severe weather statements are issued. The second severe weather statement contains the tornado emergency language for county A. As the tornado moves into county B, the NWS issues a new tornado warning, without the tornado emergency language, for county B. Subsequently, the NWS issues three severe weather statements for county B, all three containing the tornado emergency language. How many tornado emergencies will this count as?
Using my definition, even though 4 tornado emergencies were technically issued, they are all contained within the framework of only two tornado warnings. Thus this is treated as two tornado emergencies — even though this is for the same tornado.
Scenario 3: A tornado warning is issued for county A and does contain the tornado emergency text. Subsequently 2 severe weather statements are issued, both of which contain the tornado emergency language. How many tornado emergencies will this count as?
Using my definition, even though 3 tornado emergencies were technically issued, they are all contained within the framework of a single tornado warning. Thus this is treated as one tornado emergency.
Does that make sense?
With that said, there have been 143 distinct tornado emergencies issued since the first one on 3 May 1999 for south Oklahoma City, OK. The chart below breaks them down into yearly counts:
Examining tornado emergencies by NWS forecast office, the top three are
- BMX (Birmingham, AL)
- HUN (Huntsville, AL)
- JAN (Jackson, MS)
This might be a bit surprising to many who typically think of “tornado alley” as being in the central United States. Unfortunately, or fortunately, you decide, many things go into the decision to issue tornado emergencies. Some of these things include population potentially impacted and local office policies. Remember, the tornado emergency is not a formal product. It wasn’t until the last year or two that local forecast offices has official guidance in place. Bottom line, not every office uses tornado emergencies. (Also, keep in mind the magnitude of the 27 April 2011 tornado outbreak and where that was located! However, to be fair, I will say that all of the top three offices had issued tornado emergencies prior to 27 April 2011.)
The rest can be found in the chart below:
In the coming days and weeks I will be doing more analysis on tornado emergencies and will post findings as they are completed. If there is something you would like to see, leave me a comment and let me know. If I don’t already have plans to examine your request, I’ll add it to my list!
The Elusive Tornado Emergency Product
In light of this year’s extremely violent tornadoes and the reaction to them amongst the meteorological, emergency management, and social science communities, I’ve spent a lot of time thinking about the National Weather Service’s (NWS) practice of issuing tornado emergencies. For those who don’t know, this product is, in theory, designed to serve as a “more severe” tornado warning. Essentially a tornado emergency is nothing more than a regular tornado warning with a variant of the phrase, “This is a tornado emergency,” contained somewhere in the text. This phrase could be contained somewhere in the initial tornado warning or in a follow-up statement known as a severe weather statement.
Over the last few days I have been working on putting together a collection of all tornado emergencies ever issued. The first one was issued on 3 May 1999, as a severe weather statement, as the Bridge Creek F5 tornado threatened downtown Oklahoma City. Since then this product has been issued over 100 times with varying success. Much like the success of the tornado emergency product, I have had varying levels of success in tracking down all the products ever issued. So far I am fairly confident that I have collected all of the tornado emergency statements since 2005. Unfortunately I have run into a problem with tornado emergencies prior to 2005. The problem stems from the fact that the, “This is a tornado emergency,” tagline can be placed in one of several NWS text products. All initial tornado warning statements that contained this tagline are archived and I am fairly confident I’ve retrieved them all. However, obtaining severe weather statements prior to 2005 have proven elusive. (The exception to this is the severe weather statements from the Fort Worth, TX office on 28 March 2000 when a tornado emergency was issued for downtown Fort Worth, which I have found.) This is where you, the amazing people of the Internet, can help. If you are in possession of, or know of, a tornado emergency prior to 2005 that is not listed on my Tornado Emergency page, please contact me as soon as possible.
In the coming days and weeks I will be updating the Tornado Emergency page with a listing of all known tornado emergencies and eventually will provide links to all of the text products and the verification.
The NWS’ Sounding Paradox
The NOAA National Weather Service (NWS) Headquarters has issued a directive that all sounding sites in the southern, central, and eastern regions (along with Montana) are to launch soundings every 6-hours until further notice. The idea here is that the additional upper-air data will help improve numerical forecasts of hurricane Irene — and I fully agree. Ultimately, better observations being ingested into the model guidance should help model forecasts, as well as the NOAA National Hurricane Center with their forecast of the all-important question: Does Irene make landfall somewhere along the densely populated east coast of the United States? (I’ve listed the message below for your reading pleasure.)
So what’s the paradox? For years now the satellite community, as well as some inside the NWS, have argued that NWS Radiosonde (sounding) Program should be scrapped in favor of using satellite derived soundings — especially for numerical forecasts!. In fact, due to recent budget issues inside the federal government, every year there is talk of cutting, or drastically scaling back, the NWS Radiosonde Program in favor of satellite derived soundings. So here is my question:
If the satellite derived soundings are so good, why does the NWS feel the need to have 6-hourly launches for the foreseeable future to improve the numerical guidance of Irene?
I happen to work very closely with another national center that I’m sure would love to have daily 6-hourly soundings to help with their forecast responsibilities…
EDIT (0240 UTC, 25 August 2011): Don’t get me wrong, satellites have their place in aiding forecasters. However, nothing can take the place of observations, and the actions by the NWS speak louder than anything I could say.
000 NOUS42 KWNO 242215 ADMNFD SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE NWS NCEP CENTRAL OPERATIONS CAMP SPRINGS MD 2214Z WED AUG 24 2011 NWSHQ DIRECTIVE TO LAUNCH SIX-HOURLY RAOBS /SOUNDINGS/... SDM IS HEREBY RELAYING A DIRECTIVE FROM NWSHQ FOR WFO/S IN ALL OF EASTERN..SOUTHERN AND CENTRAL REGIONS PLUS MONTANA IN WESTERN REGION TO LAUNCH SIX-HOURLY RAOBS /SOUNDINGS/ BEGINNING AT THU 25 AUG 06Z AND UNTIL FURTHER NOTICE. THIS DIRECTIVE IS TO PROVIDE ADDITIONAL DATA INPUT WHICH SHOULD HELP WITH MODEL GUIDANCE IN FORECASTING THE FUTURE TRACK AND IMPACTS OF HURRICANE IRENE. $$ STOUDT/SDM/NCO/NCEP
About Patrick
Patrick Marsh is a Ph.D. student at the University of Oklahoma's School of Meteorology. He earned a Bachelors of Science in Mathematics and Physics (cum laude) from the University of Arkansas in 2005 and a Masters of Science in Meteorology in 2007. In addition to working on his doctorate, Patrick serves as the National Severe Storms Laboratory Liaison to the Hazardous Weather Testbed where his research interests lie in working with operational forecasters, data mining, data visualization, and all things high-impact weather. For more about Patrick's work, check out his complete CV!
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