SEVERE WEATHER OUTLOOK FORECAST SYNOPSIS…ISSUED FEB. 05, 2017…5:15 P.M. EST

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(T. F. “Storm” Walsh III)

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Good evening everyone!

outlook-category-descriptions

The Storm Prediction Center (SPC), Norman OK., has designated a SLIGHT risk of Severe Thunderstorms FROM THE OK/AR BORDER TO SOUTHERN IL…

There is a MARGINAL risk FROM EXTREME NORTHEAST TX TO WESTERN IN…

SPC DAY 2 CONVECTIVE OUTLOOK (LINKED)
day2otlk_1730

…SUMMARY…
Scattered severe thunderstorms are expected during the second half of the period from the Arkansas/Missouri vicinity into portions of the lower Ohio Valley area.

Analysis of the SPC outlook text indicates a fast moving shortwave trough is expected to eject across the southern Rockies, and into the KS/OK area by Monday evening (00Z or 7:00 p.m EST).  This will setup a veering LLJ (Low Level Jet).  SPC indicates strong capping to be in place through late afternoon, and by early evening, large scale forcing for ascent is forecast to enhance lapse rates, allowing for supercell development by mid evening.  Should these thunderstorms become surface based, and surface based updrafts develop, this could allow for development of a few tornadoes.

Based on forecast sounding solutions from F5 DATA software, there is quite a discrepancy in the GFS and NAM-WRF solutions.  I believe the forecast indices may be a little on the aggressive side with the NAM at the moment, and will re-evaluate soundings tomorrow, against the RAP model output, and SPC SREF solution.  However, given the premise of a capping environment for most of the day, with the probability of it eroding, or “busting”, there IS always that probability the current forecast soundings may be close.  For right now, with that in mind, the NAM-WRF suggests the strongest, and most probable severe weather threat, and isolated tornado threat, may occur over Arkansas.  This may occur after late evening, and well into early morning hours.  The following are the current forecast SWEAT values and STP values

NAM-WRF FORECAST SWEAT VALUES
f5data-nam-1am-sweat

NAM-WRF STP VALUESf5data-nam-1am-stp

SWEAT EXPLAINED
http://forecast.weather.gov/glossary.php?word=sweat

SWEAT INDEX (SEVERE WEATHER THREAT):

<272 Thunderstorms unlikely

273-299 Non-severe thunderstorms are possible

300-400 Thunderstorms will approach severe limits

401-600 Increased risk of severe storms or isolated tornadoes

601-800 Tornadoes almost always occur

STP EXPLAINED
The significant tornado parameter (effective layer) is another composite index. Like the supercell composite, it contains several ingredients. The soup that makes up the significant tornado parameter includes effective bulk wind difference, effective storm-relative helicity, 100mb mean parcel CAPE (MLCAPE), and 100mb mean parcel height (MILCL). Values greater than 1 have been associated with a majority of tornadoes that have been rated significant/strong (which is a rating of EF2 or greater). Non-tornadic supercells, on the other hand, are often associated with significant tornado parameters of less than 1.

The SPC has indicate a SLIGHT risk of Severe Thunderstorms ACROSS THE MID MISSISSIPPI/OHIO/TENNESSEE VALLEYS AND VICINITY…

There is a MARGINAL risk SURROUNDING THE SLIGHT RISK AREA…

SPC DAY 3 SEVERE THUNDERSTORM OUTLOOK (LINKED)
day3otlk_0830

…SUMMARY…
Showers and scattered thunderstorms are forecast to affect the mid Mississippi, Ohio, and Tennessee Valley areas, and later spreading eastward across the Appalachians. Isolated strong/locally severe storms will be possible mainly west of the mountains.

I am holding off on analysis of forecast soundings for day 3, until Tues. morning, given the discrepancies in current model solutions.  I will try to have an update on this on Tues. as the day 1 outlook.  From the day 3 text:

Mid MS/OH/TN Valleys and vicinity… A complex scenario remains evident for Day 3/Tuesday, with model differences still evident and corresponding low confidence with respect to forecast details of convective mode/intensity/evolution ahead of the advancing cold front.

Barring any unforeseen circumstances, I should have updates on both days.

Have a blessed evening!

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 SEVERE WEATHER OUTLOOK FORECAST SYNOPSIS…ISSUED FEB. 05, 2017…5:15 P.M. EST

  1. dellamom says:

    Thank you, Storm. Our area’s nutria (our answer to Punxsutawny Phil) predicted an early end to winter last week, instead of Phil’s longer winter prediction for his area. I hope our nutria was right.

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