WTVY-TV Viewing Area Facing Severe Weather Potential This Afternoon

By: National Weather Service and Oscar Fann WTVY-TV meteorologist
By: National Weather Service and Oscar Fann WTVY-TV meteorologist

National Weather Service Tallahassee Fl
450 Am Est Thu Jan 26 2012
Severe Weather [This Afternoon And Tonight]...

Tallahassee NWS...

Area Radars Already Show A Predominately SSE Flow In The Lowest Atmosphere Across Much Of Alabama, Georgia, And Florida.

This Should Allow For Excellent Northward Low-Level Moisture Transport Today With Dewpoints On The Rise To The Mid-60s In The Florida Panhandle To Around 70 Degrees Offshore.

Sea Surface Temps (SSTs) Over Much Of The Gulf Are Above Normal And There Haven`t Been Any Major Intrusions Of Cooler Air Masses Lately.

Therefore, There Should Not Be Much Negative Modification Of The
Air Mass As It Surges North Through The Eastern Gulf Today.

The Midnight Storm Predictions Center (SPC) Severe Weather Outlook (and recent mesoscale / regional discussion) Both Reference A Band Of
Cooling Cloud Tops Indicative Of Increasing Ascent Ahead Of The
Mid-Upper Level Closed Low That Is Just Beginning To Eject.

This Increasing Ascent Stretched From East Texas To Just Offshore Of
South Texas.

Linear Extrapolation (that is, local time arrival of the active weather) Would Have This Arriving Over Western Alabama By Noon CST, And The Western Part Of Our Forecast Area By 3-4 pm CST.

As The Stronger Deep Ascent And Surging Cold Front Catch Up To The Squall Line Later This Morning, There Is Expected To Be An Increase In Storm Intensity.

Timing Of The Eastward Motion Of This Squall Line Has Sped Up Relative To Computer / Model Solutions This Time Last Night.

However, Six Individual High-Resolution Model Solutions Are Tightly Clustered Around The Following Timeline:

Storms Arrive At Our Western Border Around 3-4 pm CST...
Reach The Apalachicola River Around 5-6 pm CST...
Advance Into The Eastern Portions (While Weakening) By 10-11 pm EST.

This Faster Approach Would Put The Storms In The Western Half Of Our Area At A Much More Climatologically Favorable Time Of Day For Severe Weather.

The Convective Mode, Fast Storm Motions, And 40-50kt Southwesterly
Low level Jet All Favor Damaging (Straight-Line) Winds As The Primary Severe Weather Threat.

The Latest Run Of Our Local Computer Model (Wrf-Arw) Shows About A 45mph West-East Movement Of The Squall Line Across Our Area.

There Is A Notable Decrease In Storm Intensity (As Approximated By Model Simulated Updraft Velocities) After 6 pm CST As The Storms Move Into The Eastern Half Of Our Area.

While A Severe Weather Threat Exists Over Our Entire Area Today, The Odds Are Higher For The Western Half As Compared To The Eastern Half.

The Wind Shear Is Also Expected To Be Strong Enough To Support
Supercellular Storms, And The Strength Of The Shear Profile In The
Low Levels Suggests A Threat For Line Mesovorticies And Tornadoes.

(OSCAR NOTE - Mesovorticies are small but powerful swirls of wind that are spun off of strong / severe thunderstorms.

It is thought not many severe thunderstorms create such violent swirls.

Nevertheless, these swirls generally last only a few seconds but can cause significant localized damage.

Often these swirls dissipate prior to reaching ground level, and the swirls reaching the ground quickly lose their energy, but not before that energy threatens anyone or anything it impacts).

Tallahassee NWS...

We Will Be In A Favorable Parameter Space For Tornadoes.

The Bulk Of The Cape (energy for storm intensity) Profile Will Be Concentrated In The Lowest 3-4km Agl (above ground level), Which Should Make Up For The Marginal Values (500 J/Kg Or So).

Four Out Of The Eight Available High Resolution Models Indicated
There May Also Be Some Discrete Cells That Form Over The Gulf And
Then Approach Our Coastal Zones Earlier In The Afternoon.

This Is Around The Time That Low-Level Shear And Cape Profiles Markedly Improve, So Any Discrete Cells Prior To A Primary Squall Line
Would Likely Be Supercellular And Have A Greater Risk To Produce
Tornadoes.

(OSCAR NOTE - First, be aware the most favorable area for the tornadic t-storms is over the Gulf waters and near the coast...

Discrete cells are always the big concern with severe weather potential.

These are individual t-storms that form well out in front of a trailing squall line of t-storms.

These separate (discrete) storms can harness all of the surrounding atmospheric energy and can become quite intense.

If there is a tornadic threat overall, then usually the tornadoes are spawned by such storms.

In a moderate to high risk outlook of severe weather, more often than not, such discrete t-storms will form.

However, in a slight risk (as is our area later today) it remains to be seen if such discrete t-storms will develop - but again, the threat for such is nearer the coastline.

A squall line of t-storms will have very gusty winds, often near the speed at which the squall line itself is moving.

Since the predicted speed of the squall line moving east at 40 to 45 mph, the it is reasonable to calculate ground winds of 30 to 40 mph will be likely - with some locations experiencing winds approaching severe limits of near 60 mph.

T-storms within a squall line can produce a tornado, but usually it is short lived.

Nevertheless, you can see there are numerous scenarios for strong t-storms in our area this afternon and early evening, so be prepared and form your severe weather PLAN NOW, so you can implement it when a WARNING is issued. When a WARNING is issued and a storm does hit you, you likely will HAVE ONLY MINUTES TO REACT, not enough time to plan.

Keep it to WTVY-TV for the latest....Oscar).


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