URGENT SEVERE WEATHER FORECAST SYNOPSIS…PUBLIC SEVERE WEATHER OUTLOOK ISSUED…FEB. 28, 2017…1:40 P.M. EST

Disclaimer:  This site is not affiliated with the National Hurricane Center, Hurricane Hunters, Storm Prediction Center, or National Weather Service.  ALL forecasts herein are the result of my analysis, and I am solely responsible for the content.
(T. F. “Storm” Walsh III)

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Good day everyone!

*QUICK NOTE:  I have updated the F5 DATA map outlines, from the 18Z run of the NAM-WRF model, as well as the new outlook text from SPC 2000Z update

PUBLIC SEVERE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1050 AM CST TUE FEB 28 2017

…Severe thunderstorms expected over parts of the Ozarks region to the Ohio Valley late this afternoon into tonight…

* LOCATIONS…
Indiana
Western and northern Kentucky
Southern and eastern Missouri
Illinois
Northern Arkansas
Northwest Tennessee
Far western Ohio
Far southeast Iowa

* HAZARDS…
Several tornadoes, a few intense

Widespread large hail, some baseball size
Scattered damaging winds

* SUMMARY…
A widespread area of severe thunderstorms is expected to develop from portions of the lower Mississippi Valley to the Ohio Valley through tonight. Strong tornadoes will be possible, especially across portions of the lower and middle Ohio Valley. Otherwise, large hail and damaging winds are expected.

Preparedness actions…
Review your severe weather safety procedures for the possibility of dangerous weather today. Stay tuned to NOAA Weather Radio, weather.gov, or other media for watches and warnings. A tornado watch means that conditions are favorable for tornadoes to form during the next several hours. If a tornado warning is issued for your area, move to a place of safety, ideally in a basement or interior room on the lowest floor of a sturdy building.

The Storm Prediction Center (SPC) has designated the following risk area regarding the Day 1 Convective Outlook:

STORM PREDICTION CENTER LINK
(http://www.spc.noaa.gov/)

…THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER EAST-CENTRAL/SOUTHEAST MISSOURI…CENTRAL/SOUTHERN ILLINOIS…CENTRAL/SOUTHERN INDIANA…AND WESTERN INTO NORTH-CENTRAL KENTUCKY…

…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SURROUNDING THE MODERATE RISK FROM THE OZARKS OF MISSOURI AND ARKANSAS INTO NORTHERN PARTS OF ILLINOIS AND INDIANA…FAR WESTERN OHIO…AND SMALL PARTS OF KENTUCKY AND NORTHWEST TENNESSEE…

…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK FROM EASTERN OKLAHOMA AND SOUTHERN ARKANSAS INTO EASTERN KENTUCKY…

…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE SLIGHT RISK INCLUDING ACROSS THE TENNESSEE VALLEY INTO THE SOUTHERN APPALACHIANS…

SPC DAY 1 CONVECTIVE OUTLOOK

TORNADO PROBABILITY
day1probotlk_2000_torn

Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 – EF5 tornadoes within 25 miles of a point. 

HAIL PROBABILITY
day1probotlk_2000_hail

Probability of one inch diameter hail or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of two inch diameter hail or larger within 25 miles of a point.

DAMAGING WIND PROBABILITY
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.

SPC THUNDERSTORM OUTLOOK 0000Z – 0400Z
enh_0000

0400Z – 1200Z

SPC SUMMARY
A widespread area of severe thunderstorms is expected to develop from portions of the lower Mississippi Valley to the Ohio Valley through tonight. Strong tornadoes will be possible, especially across portions of the lower and middle Ohio Valley. Otherwise, large hail and damaging winds are expected.

Little in the way of changes have been made to the ongoing outlook. Latest observational trends and model guidance including CAMs indicate initial warm sector storm development is beginning over southern Missouri, with additional storm initiation expected over parts of northwest Arkansas, extreme southeast Kansas, western/northern Missouri into southern Iowa. This activity will be located within a strongly sheared and unstable environment that will promote development of supercells capable of large hail, damaging winds and tornadoes. The initial Missouri activity is likely to intensify as storms develop and spread eastward/east-northeastward into an increasingly broad warm sector extending across the mid-South and into the lower/middle Ohio Valley, as a strengthening low-level jet expands across this region. CAM guidance suggests that some of the initial storms will maintain discrete cell characteristics into the overnight hours as the leading edge of storms moves into the Ohio Valley, with a continued threat for all severe hazards including possible strong tornadoes.

Other severe storms are likely to develop by 00-02Z near the cold front with a scattered to broken line forming in the wake of the initial warm sector activity. The QLCS is expected to progress eastward through the overnight hours with the strongest storms capable of damaging winds and large hail. In addition, the QLCS will need to be monitored for embedded supercells and/or mesovortices with an attendant threat for a few tornadoes to occur.

Based on my analysis of information contained in the SPC Outlook, and analysis of the RAP, GFS and NAM-WRF models against initial Mesoscale analysis, the NAM-WRF on the 18Z run represented the SPC outline somewhat better than the other 2 models based on advancing each out into the forecast period.  This is not to say the RAP may show some correction, however I am going with the NAM-WRF as the choice, as the current RAP model only goes out to 12 a.m. CST, and the GFS shows weakening parameters close to and after midnight, which does not correlate with the SPC outlook in mentioning the potential for nocturnal significant tornadoes.  A SIGNIFICANT tornado is considered to be in the range of EF2 to EF3.  Violent tornadoes are rated EF4 to EF5.

Based on the information analyzed from SPC, and analysis of F5 DATA NAM-WRF severe weather parameters and indices, The following outlined maps indicate where the model is determining the best probability for the most severe supercells and  highest probability of strong-long tracked tornadoes may occur.  Based on the SPC Thunderstorm Outlook maps however, It appears the models may be initializing development a little too soon.  It is suggested that initiation may occur closer to late afternoon to early evening.  Based on variations and discrepancies in comparing all 3 models, the outlines are an “approximation”.  These storms / tornadoes could very well occur within the SPC current outlines in the posted outlook maps.

NAM-WRF 6:00 P.M. CST
f5data-nam-6pm-cst

NAM-WRF 9:00 P.M. CST
f5data-nam-9pm-cst

NAM-WRF 12:00 A.M. CST
f5data-nam-12am-cst

NAM-WRF 3:00 A.M. CST
f5data-nam-3am-cst

The following was the GFS 6:00 P.M. CST map for comparisonf5data-gfs

The following were indices noted from the forecast soundings which will be ongoing the majority of this event:

SBCAPE: 1000 – 2500 J/KG
MLCAPE: 500 – 1500j/kg
3KM HELICITY: 350 – 450 m2s-2
STP: 6 – 15
CRAVEN BROOKS INDEX: 50,000 – 90,000
SHOWALTER INDEX: -2 to -6
LIFTED INDEX: -6 to -10
SWEAT INDEX: 400 – 550

Based on this and SPC information…this event has the potential to become a PDS (Particularly Dangerous Situation).  SPC outlook maps and forecast sounding indices support large damaging hail, strong damaging straight line winds, and strong-long tracked tornadoes.  For my storm chaser friends…PLEASE USE EXTREME CAUTION TODAY!

Residents within the ENHANCED and MODERATE risk areas should closely monitor the progress of this situation via NOAA Weather Radio, local news outlets, and local NWS office statements and warnings.

IF A TORNADO WARNING IS ISSUED FOR YOUR AREA…SEEK SAFE SHELTER IMMEDIATELY

The following graphics are linked for you to receive up to date information on SPC Watches and Mesoscale Discussions.  The NWS Hazard and Warning Display is linked.  Click on the map, and then click on your area for up to date NWS Statements and Warnings. PLEASE, visit back often and click on the graphics for current, up to date information…it may help save your life!

SPC CONVECTIVE WATCHES
validww

SPC MESOSCALE DISCUSSIONS
validmd

NWS HAZARD AND WARNING DISPLAY

NWS DOPPLER RADAR SITE
ridge_sitemap

I intend to have an update on the Wednesday outlook, however I will not be able to begin analysis until after 12:30 p.m., due to a doctor appointment and other commitments.

Have a blessed day!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS
CoCoRAHS OBSERVER

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About palmharborforecastcenter

I am a Tropical Forecast meteorologist, providing hurricane forecasts during the Atlantic Hurricane Season. I retired from the U.S. Coast Guard in July of 2001. Meteorology became my passion in high school, and I have continued my educational background in meteorology since 1996, when I undertook the study of Tropical Meteorology. While working toward my degree, I had to unexpectedly withdraw from college due to my oldest sons medical reasons. I do however, meet the educational criteria of the AMS to be recognized as a meteorologist. Studies include, but are not limited to the Navy Aerographers Mate course, Naval METOC meteorology course, Meteorology 2010 Sophomore level course while attending St. Petersburg College, Clearwater, FL., Basic Forecasting course for operational meteorologists from Rapid WX, meteorology institute, a four month meteorological internship, and extensive research on numerous meteorological topics such as the MJO, NAO, satellite imagery interpretation, etc. I have been forecasting Tropical Weather (Tropical Storms and Hurricanes) since 1996, with my main client being three different Coast Guard Commands.
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2 Responses to URGENT SEVERE WEATHER FORECAST SYNOPSIS…PUBLIC SEVERE WEATHER OUTLOOK ISSUED…FEB. 28, 2017…1:40 P.M. EST

  1. originallt says:

    Strong/severe storms further East today. Wed. Right now a strong line moving thru W. Va. at 10am.

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