MODERATE SEVERE THUNDERSTORM RISK…STRONG TORNADOES POSSIBLE SYNOPSIS…ISSUED MAR. 23, 2023…8:40 P.M. EDT6 min read
Disclaimer: This 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, (to which you will see me at times, insert excerpts from various agencies due to the nature of the importance of the information) and I am solely responsible for the content. As ALWAYS, follow the National Hurricane Center, National Weather Service, and your local Emergency Management officials for emergency decisions. In addition, this is strictly a FORECAST OFFICE. I CANNOT make decisions regarding travel plans, etc. My purpose, is to provide you the information, based solely on information I analyze, and the accuracy of the information at hand of the time of analysis, so you may make informed decisions.
(T. F. “Storm” Walsh)
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I will reiterate, my forecasts are based on the available information at the time of analysis, and are only as accurate as the information analyzed and the solutions provided.
The outlined maps you were used to seeing from my F5 DATA software, are no longer around and operational. This means I have lost quite a bit of data to analyze but I will try to make the severe weather forecasts as accurate and understandable as possible.
The Storm Prediction Center (SPC), has issued a MODERATE risk of severe thunderstorms OVER PARTS OF THE LOWER MISSISSIPPI VALLEY…
Severe thunderstorms are likely from the Lower Mississippi Valley toward the lower Ohio Valley Friday afternoon and evening. Tornadoes, some strong, as well as damaging winds and hail are expected.
SPC DAY 2 SEVERE THUNDERSTORM OUTLOOK MAPS (THIS MAP LINKED)
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.
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% or greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Based on my analysis this evening of the SPC DAY 2 Convective Outlook, and severe weather and tornado indices, all severe threats will be probable for tomorrow. A brief summary of the analysis indicates veering winds from the surface (southerly) up through the 850 – 500 mb level. Winds are forecast to increase to 50 – 70 kts at 850 mb, and 75 – 95 kts at 500 mb. This will aid in some favorable wind shear which lends itself to helicity or rotation in the atmosphere. Forecast hodograph soundings indicated long hodographs, which are favorable for tornadoes. While not strong, moderate CAPE values and lifted index indicate the atmosphere will be buoyant enough for severe thunderstorms and supercells to develop. I am not expecting large, severe hail at this time, however conditions can change. Strong, long tracked tornadoes are possible, and should be most probable within the moderate and enhanced risk areas. Based on analysis of the NAM model 18Z run, storms should begin to initiate at around 3:00 p.m. CDT. As the afternoon progresses, the low level jet will strengthen quickly, and storms are forecast to become stronger, with the threat of tornadoes increasing between 7:00 p.m. (FRI.) through 1:00 a.m. (SAT.) CDT. You will note this in the NAM SCP and STP animations. Residents within the risk areas should monitor NOAA Weather Radio closely, along with their local news and NWS office
NAM 500 MB WIND FORECAST
NAM 700 MB WIND FORECAST
NAM 850 MB WIND FORECAST
The following forecast indices and parameters were observed in analysis this evening for the risk area. Depending on how exactly the situation develops, and degree of daytime heating, these values CAN change between now and the 12Z model run:
SBCAPE: 1000 – 1500 j/kg-1
MLCAPE: 1000 – 1500 j/kg-1
MUCAPE: 1500 j/kg-1
SRH: 300 m2/s2
L. I.: -3 to -5
MOST UNSTABLE L. I.: -3 to -6
STP: 1 to 4
SCP: 1 to 8
EFF. SHEAR: 40 – 50KTS
MID LEVEL LAPSE RATE: 7.0 – 7.5C
DEWPOINT: 60F – 70F
STP ( Significant Tornado Parameter) EXPLAINED:
A majority of significant tornadoes (EF2 or greater damage) have been associated with STP values greater than 1, while most non-tornadic supercells have been associated with values less than 1 in a large sample of RAP analysis proximity soundings.
SCP (Supercell Composite Parameter) EXPLAINED:
A multiple ingredient, composite index that includes effective storm-relative helicity (ESRH, based on Bunkers right supercell motion), most unstable parcel CAPE (muCAPE) and convective inhibition (muCIN), and effective bulk wind difference (EBWD). Each ingredient is normalized to supercell “threshold” values, and larger values of SCP denote greater “overlap” in the three supercell ingredients. Only positive values of SCP are displayed, which correspond to environments favoring right-moving (cyclonic) supercells.
The following sites will explain most of these values, and will give you an idea of what to expect:
ENVIRONMENTAL INDICES AND PARAMETERS NWS
THE WEATHER PREDICTION
Please visit the SPC main site at the following link for tomorrow’s activity:
SPC HOMEPAGE LINK
The following are animations of both the SCP and STP currently for tonight, however slight changes are possible between now and tonight’s model run. The animation runs from 3:00 p.m. to midnight CST. The greater the value, the greater the risk to an area.
NAM MODEL SCP FORECAST
NAM MODEL STP FORECAST
Please visit my site again for the severe event to use the following maps, which should update automatically, for Mesoscale Discussions and Convective Watches. You may have to refresh your browser, or click on the graphics. I have provided the SPC homepage link above, so you may get the updated information regarding any changes to the outlook:
SPC MESOSCALE DISCUSSIONS (CLICK IMAGE FOR UPDATES)
SPC CONVECTIVE WATCHES (CLICK IMAGE FOR UPDATES)
IF A TORNADO WARNING IS ISSUED FOR YOUR AREA, IMMEDIATELY TAKE STURDY AND SAFE SHELTER
The following NWS Watch / Warning map will provide local NWS information for your area. Click the image, then once it refreshes, click on your area of interest to view any special weather statements, hazards or advisories for your area.
NWS WATCH / WARNING DISPLAY (LINKED…CLICK MAP, THEN YOUR AREA)
WSI DOPPLER RADAR LOOP (LINKED)
RAP RADAR (CLICK IMAGE THEN GO TO LOOP DURATION AND PICK LENGTH OF LOOP, THEN CLICK RADAR SITE)
You may direct any questions by contacting me personally, ANYTIME, at: firstname.lastname@example.org
Have a blessed evening!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
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