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(T. F. “Storm” Walsh)
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Please be aware, even though I do not post every night, rest assured I am continuously monitoring various areas for any significant weather. I will be taking Sundays off (family time), unless we have active systems that may be posing a threat (i.e. Tropical, Winter Weather, Coastal Storms, etc.).
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 Storm Prediction Center (SPC), has issued an ENHANCED RISK OF SEVERE THUNDERSTORMS in the current DAY 2 outlook: FROM PORTIONS OF FAR SOUTHEAST NEBRASKA INTO CENTRAL/EASTERN KANSAS AND NORTH-CENTRAL OKLAHOMA…
Severe thunderstorms capable of all hazards are possible Friday afternoon into Friday night across portions of the southern and central Plains into the lower Missouri Valley.
Very little change in the overall thinking of the forecast compared to the earlier Day 2 outlook issuance. A strong mid- to upper-level speed max will quickly move southeast from the eastern Great Basin into the central/southern Plains during the period. In the low levels, a surface low initially over the central High Plains will develop east into central KS by mid afternoon before moving to southeast SD by daybreak Saturday. A triple point over KS during the day will feature a north-south dryline into the southern Great Plains near/immediately west of the OK I-35 corridor. A cold front will push east/southeast across KS and into OK Friday night.
SPC DAY 2 CONVECTIVE OUTLOOK LINK:
SPC DAY 2 CONVECTIVE OUTLOOK
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 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 THUNDERSTORM WIND PROBABILITY
Based on my analysis of the SPC DAY 2 Outlook, SPC indicates significant height falls at 500 mb by early evening. During mid afternoon, into the evening hours, increasing low level flow from the south, will transport ample moisture into the area, with dewpoints forecast to be in the mid to upper 6o’sF. This, combined with a low to mid level flow (700 mb) of 40-50 kts,and ample lift within a very unstable boundary layer, will support an environment capable of producing very large to giant hail (2-3 inches in diameter), and tornadoes, with some isolated that could be intense over the ENHANCED risk area. Be advised however, strong tornadoes have been known to develop outside of an ENHANCED risk area.
Based on my analysis of both the NAM-WRF model from F5 DATA, and the NAM 3 km model, the following forecast severe and tornado indices were analyzed and values represent a blend of both models:
SBCAPE: 2000 – 3500 j/kg
MLCAPE: 1000 – 2500 j/kg
SRH: 200 – 300 m2/s2
L. I.: -4 to -8
SWEAT: 375 – 500
EHI: 1 – 4
VGP: 0.2 – 0.5
STP: 1 – 4
A majority of significant tornadoes (F2 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.
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.
VGP: The VGP (Vorticity Generation Parameter) is meant to estimate the rate of tilting and stretching of horizontal vorticity by a thunderstorm updraft. Values greater than 0.2 m s-2 suggest an increasing possibility of tornadic storms.
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
The following outlined areas indicate where the modeling suggests the best / highest probabilities for the strongest severe weather and tornadoes could occur. The strongest of the indices will be located where the SPC has the 10% / hatched area probability for significant tornadoes. Based on analysis of the indices, the values begin to increase at around 1:00 p. m. CDT, continuing to increase and reaching their peak between 4:00 p. m. – 10:00 p. m. CDT, then slowly diminishing:
F5 DATA NAM – WRF 1:00 P. M. CDT
4:00 P. M. CDT
7:00 P. M. CDT
10:00 P. M. CDT
The following NAM 3km animations indicate the locations and strength of the forecast STP (Significant Tornado Parameter) index, and SCP (Supercell Composite Parameter) index.
NAM 3km STP ANIMATION (1:00 P. M. CDT APR 29 – 10:00 P. M. CDT APR 29)
NAM 3km SCP ANIMATION
Please use the following maps for all days, which should update automatically, for Mesoscale Discussions and Convective Watches. You may have to refresh your browser, or click on the graphics. I am also providing the SPC homepage link, 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)
SPC HOMEPAGE LINK
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 RADAR SITE)
You may direct any questions by contacting me personally, ANYTIME, at: email@example.com
Have a blessed evening!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
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