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SLIGHT RISK SEVERE THUNDERSTORM OUTLOOK…ISSUED NOV. 21, 2023…9:15 A.M. EST

5 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.
https://www.spc.noaa.gov/new/images/SPC_outlook_final_updated.png

The Storm Prediction Center (SPC), has issued a SLIGHT risk of severe thunderstorms:
ACROSS SOUTHERN ALABAMA…SOUTHWESTERN GEORGIA AND PARTS OF THE FLORIDA PANHANDLE…

…SPC SUMMARY…
A few tornadoes and isolated damaging gusts are possible today across southern Alabama, southwestern Georgia and parts of the Florida Panhandle. Isolated damaging gusts are possible, along with a marginal tornado threat, from there northeastward to the coastal Carolinas.
SPC DAY 1 SEVERE THUNDERSTORM OUTLOOK MAPS (THIS MAP LINKED)
day1otlk_1300
TORNADO
day1probotlk_1300_torn
HAIL
day1probotlk_1300_hail
DAMAGING WINDS
day1probotlk_1300_wind
Rain and thunderstorms, some with detected rotation based on Doppler Radar SRV, were already ongoing at the time of this analysis.  Based on my analysis this morning of the SPC DAY 1 Convective Outlook, severe weather and tornado indices from the NAM and CIPS guidance, all severe threats will be possible this afternoon through tonight and into early morning.  A brief summary of the analysis indicates veering winds from the surface (southerly) to SWLY at the 850 mb level, to WSW from 500 mb to the upper level.  This will aid in some moderately favorable wind shear of 50 – 60 kts and effective shear of 30 – 40 kts, which helps to create helicity or rotation in the atmosphere and supercells.  Although analysis indicated a weaker mid level lapse rate than yesterday, shear and storm relative helicity values could produce tornadoes.  Based on analysis of the significant tornado parameter values, energy helicity index combined with the SRH, I cannot rule out an isolated strong tornado within the slight risk area.  Based on forecast animations, this activity should shift east into South Carolina by 12:00 noon – 3:00 p.m. CST…1:00 p.m. – 4:00 p.m. EST.  Depending on exactly how the situation develops, and degree of daytime heating, these values could change between now and this evening:
SBCAPE: 750 – 1000 j/kg-1
MLCAPE: 250 – 1000 j/kg-1
MUCAPE: 250 – 1000 j/kg-1
SRH: 250 – 700+ m2/s2
L. I.: -1 to -3
STP: 1 to 4
SCP: 1 to 8
EFF. SHEAR: 30 – 40 kts
0 -6 km SHEAR: 50 – 60 kts

MID LEVEL LAPSE RATE: 6.0C
DEWPOINT: 60F – 71F
EHI: 2.5 – 3.0
TOTAL TOTALS INDEX: 48

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
https://www.weather.gov/lmk/indices

THE WEATHER PREDICTION
http://www.theweatherprediction.com/severe/indices/

SPC HOMEPAGE LINK
https://www.spc.noaa.gov/classic.html

The following are animations of both the SCP and STP  The animation runs from 9:00 a.m. to 3:00 p.m. CST.  The greater the index value, the greater the risk to an area for supercell and tornado development, and greater risk for stronger of the both.
NAM MODEL SCP FORECAST
nam-nest-alms-supercell_comp-1700546400-1700578800-1700600400-80
NAM MODEL STP FORECAST
nam-nest-alms-sig_tor-1700546400-1700578800-1700600400-80
The following graphic from the SREF model indicate the time and probability of STP values greater than one. 
A majority of significant tornadoes (EF2 or greater damage) have been associated with STP values greater than 1
STORM PREDICTION CENTER PROBABILITY FOR STP VALUES >1
SREF_prob_supercomp_1__f015
The following maps, 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)
Valid MD Image
SPC CONVECTIVE WATCHES (CLICK IMAGE FOR UPDATES)
Valid WW Image
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)

NWS DOPPLER RADAR LOOP (LINKED, CLICK RADAR MAP)
canvas.RADR.US
RAP RADAR (CLICK IMAGE THEN GO TO LOOP DURATION AND PICK LENGTH OF LOOP, THEN CLICK RADAR SITE)
CARIBBEAN RADAR (CLICK IMAGE)
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You may direct any questions by contacting me personally, ANYTIME, at: twalsh22000@yahoo.com

Have a blessed evening!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST

palmharborforecastcenter

2023-11-21 14:11:54

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