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March 20-23 Severe Threat


Jim Martin

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storm is about 20 miles southwest of where I saw my first tornado.

kind of surprised LBB office tor warned that given probably high bases thanks to the high T/Td spreads, never has had that good of rotation at low levels, all convergent.

BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE LUBBOCK TX

701 PM CDT SAT MAR 19 2011

THE NATIONAL WEATHER SERVICE IN LUBBOCK HAS ISSUED A

* TORNADO WARNING FOR...

SOUTHWESTERN FLOYD COUNTY IN NORTHWEST TEXAS.

SOUTHEASTERN HALE COUNTY IN NORTHWEST TEXAS.

NORTHWESTERN CROSBY COUNTY IN NORTHWEST TEXAS.

* UNTIL 730 PM CDT

* AT 657 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A FUNNEL CLOUD 10

MILES WEST OF PETERSBURG...OR ABOUT 6 MILES NORTHEAST OF

ABERNATHY...MOVING EAST AT 20 MPH.

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Tony I see you lurking..any thoughts?

I'm wary of that...I don't know if the cap will break along/S of the warm front w/o a substantial lift mechanism...there is subtle lift but will it be enough? If it is, I could even see a strong (~EF2) tornado result in srn IA...but I just personally don't really see it happening...

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DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1230 AM CDT SUN MAR 20 2011

VALID 201200Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM NRN MO/SRN IA INTO NWRN

IL...

..NERN KS INTO NRN MO...IA...NRN IL

WIDESPREAD SHOWERS AND ELEVATED THUNDERSTORMS ARE EXPECTED TO BE

ONGOING SUN MORNING ACROSS ERN IA..SRN MN...SRN WI AND NRN IL IN A

STRONG WARM ADVECTION REGIME ON THE NOSE OF A 50+ KT LOW LEVEL JET.

THESE STORMS ARE NOT EXPECTED TO BE SEVERE...BUT SMALL HAIL CANNOT

BE RULED OUT GIVEN MINIMAL MELTING/RELATIVELY COOL BOUNDARY LAYER

PROFILES.

THIS INITIAL ACTIVITY SHOULD END FROM W TO E...BUT MAY PERSIST OVER

NRN IL INTO SRN WI/MI N OF THE WARM FRONT. SOME HEATING AND

DESTABILIZATION IS EXPECTED TO OCCUR TOWARDS THE MO RIVER AHEAD OF

THE APPROACHING COLD FRONT...WITH BOTH THE COLD FRONT AND

CONVECTIVELY REINFORCED WARM FRONT TO THE E ACTING AS FOCI FOR

REDEVELOPMENT. AMPLE FLOW/DEEP SHEAR WILL EXIST FOR STRONG TO SEVERE

STORMS...INCLUDING SUPERCELLS PRODUCING LARGE HAIL AND BOWING LINE

SEGMENTS PRODUCING DAMAGING WIND GUSTS. LOW LEVEL SHEAR WILL BE

MAXIMIZED ALONG THE WARM FRONT...WHICH COULD RESULT IN A BRIEF

TORNADO BUT STORMS SHOULD BECOME ELEVATED AS THEY CROSS THE BOUNDARY

WITH A REMAINING HAIL THREAT.

THERE IS UNCERTAINTY WITH HOW FAR WEST DEVELOPMENT WILL OCCUR ALONG

THE COLD FRONT DUE TO THE UPPER WAVE PASSING BY...FROM NERN KS INTO

NWRN MO. THUS...WILL KEEP ONLY MINIMAL SEVERE PROBABILITIES IN THESE

AREAS FOR MARGINAL HAIL/WIND DURING THE EVENING.

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looking at the 12z RUC alone I would say any chance and something to spin and possibly produce a tornado would be extreme eastern IA into northwest IL from DBQ to to east of DVN where the sfc winds are better on the nose of the instability and theta-e axis.

It is pushing the front through IA quickly with westerly 850's all the way to IOW by 0z. No turning from H85 to H5 is a problem, there a bit more southwesterly the closer you get to IL. Also going to have to watch clearing obviously.

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DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1127 AM CDT SUN MAR 20 2011

VALID 201630Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF

KS/MO/IA/IL/WI...

SOUTHWESTERLY MID LEVEL FLOW IS PRESENT TODAY OVER MOST OF THE

PLAINS AND MS VALLEY...WITH WATER VAPOR IMAGERY SHOWING A

WELL-DEFINED SHORTWAVE TROUGH MOVING ACROSS SD/NEB. THIS FEATURE IS

EXPECTED TO MAINTAIN A RISK OF SHOWERS AND THUNDERSTORMS OVER

PORTIONS OF THE MIDWEST AND MID/UPPER MS VALLEY TODAY AND TONIGHT.

THIS IS ALSO THE AREA MOST LIKELY TO SEE ISOLATED SEVERE STORMS.

..IA/MO/IL/WI

A LARGE CLUSTER OF SHOWERS AND THUNDERSTORMS HAS BEEN ONGOING FOR

MANY HOURS...MOVING FROM THE CENTRAL PLAINS INTO THE UPPER MS

VALLEY. STRONG HEATING HAS COMMENCED ALONG THE SOUTHERN EDGE OF

THIS PRECIP SHIELD OVER PORTIONS OF IA/MO AND INTO CENTRAL IL.

STRONG SOUTHERLY LOW LEVEL WINDS ARE ALSO HELPING TO

MOISTEN/DESTABILIZE THIS REGION WITH DEWPOINTS CLIMBING INTO THE 50S

ACROSS PORTIONS OF MO. THIS TREND WILL PERSIST THROUGH THE

AFTERNOON WITH HEATING/MOISTENING AND SOME DESTABILIZATION OCCURRING

AS FAR NORTH AS THE WI/IL BORDER.

MOST MODEL SOLUTIONS AGREE ON THE RE-DEVELOPMENT OF THUNDERSTORMS

THIS AFTERNOON IN THE WAKE OF THE MORNING MCS AND AHEAD OF THE

APPROACHING UPPER TROUGH. ACTIVITY SHOULD INTENSIFY ALONG THE

SURFACE BOUNDARY OVER CENTRAL IA AND SPREAD EASTWARD ACROSS PORTIONS

OF NORTHERN/CENTRAL IL. ALTHOUGH INSTABILITY WILL BE

LIMITED...FAVORABLE VERTICAL SHEAR AND COLD TEMPERATURES ALOFT WILL

PROMOTE A RISK OF HAIL AND GUSTY/DAMAGING WINDS IN THE STRONGEST

STORMS. THE EASTERN EXTENT OF THE SEVERE THREAT IS UNCERTAIN...BUT

LATEST HRRR SOLUTIONS SUGGEST SUFFICIENT DESTABILIZATION FOR A RISK

OF SEVERE WEATHER AS FAR EAST AS THE CHI AREA.

..KS/OK

THE SURFACE DRYLINE WILL EXTEND SOUTH-SOUTHWESTWARD FROM IA INTO

CENTRAL KS AND NORTHWEST OK BY LATE THIS AFTERNOON. FULL SUNSHINE

AND STEEP MID LEVEL LAPSE RATES MAY BE SUFFICIENT TO LOCALLY

ELIMINATE THE CAP...ESPECIALLY OVER EASTERN KS WHERE WEAK UPWARD

FORCING IS ALSO EXPECTED. ANY STORMS THAT FORM ALONG THIS AXIS WILL

POSE A THREAT OF DAMAGING WINDS AND HAIL. THE MOST LIKELY TIME

WINDOW FOR THIS THREAT WOULD BE 23-02Z.

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Well I have to live these vicariously through you guys now. I'll heading into work in an hour and will definitely be following along this evening. :popcorn:

We always appreciate your input. :thumbsup:

The surface winds do look to veer south-southwesterly later this afternoon. The thing I like though is the steady progression of stronger winds as you go higher in the column. Very smooth looking hodo. Also, the H5 winds of 55+kts are screaming in from almost due westerly. The added bonus of 100+kts above H3 over northern Iowa later today will only help matters. I'm definitely still pretty intrigued by this setup. It's close enough that even though there are some doubts I may have to run out west of Iowa City here a bit later.

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We always appreciate your input. :thumbsup:

The surface winds do look to veer south-southwesterly later this afternoon. The thing I like though is the steady progression of stronger winds as you go higher in the column. Very smooth looking hodo. Also, the H5 winds of 55+kts are screaming in from almost due westerly. The added bonus of 100+kts above H3 over northern Iowa later today will only help matters. I'm definitely still pretty intrigued by this setup. It's close enough that even though there are some doubts I may have to run out west of Iowa City here a bit later.

Most of the globals were showing that really nice jet streak punching over the top of Iowa later today. The veering is definitely concerning, but a few of the globals were hinting at a sort of meso low along the IA/MO border that might back winds in a relative sense to the ambient flow. HRRR is showing what appears to be a broken line of supercells with the latest run.

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Some nice hailers possible later today from Quad Cities over to Chi town. Spring has arrived with the start of the svr season. Looks rather active this week. Offer your comments OceanStwx and check in as needed from Down East. I do wonder about moisture, though. Dews are presently pretty low quite the mileage south from the area.

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Some nice elevated looking towers floating overhead right now. Some clearing is visible off to the south. The main tornado threat will remain west of the QC, but if we can get something to pop near the warm front later on there is a small chance we could see something decent even here. SRH will be better near the Mississippi, but instability will be lacking compared to areas further west. Going to be an interesting afternoon/eve.

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Some nice elevated looking towers floating overhead right now. Some clearing is visible off to the south. The main tornado threat will remain west of the QC, but if we can get something to pop near the warm front later on there is a small chance we could see something decent even here. SRH will be better near the Mississippi, but instability will be lacking compared to areas further west. Going to be an interesting afternoon/eve.

Ya only shot at a tornado is going to be if/when a storm can cross the warm front and ingest better vorticity. After that it will cross it and go elevated.

sunshine should be here by 2pm.

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LOT HWO

BUT THERE IS A POSSIBILITY THAT A FEW STORMS COULD BECOME SEVERE TOWARD

LATE AFTERNOON OR EVENING. A LOW PRESSURE SYSTEM PASSING NORTH

OF THE AREA WILL DRAG A COLD FRONT THROUGH OVERNIGHT. INCREASING

INSTABILITY AND LIFT AHEAD OF THE FRONT THIS EVENING...TOGETHER

WITH THE STRONG WIND FIELD ALREADY IN PLACE...COULD SUPPORT

SUPERCELLS WITH LARGER HAIL AND STRONG WIND GUSTS.

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The warm front just passed through here. We've shot up from 49 to 53 over the past 10 minutes.

Latest RUC continues to break the cap and initiate convection along the cold front around 20-21z. Surface dews continue to steadily increase in the warm sector in southern Iowa. Most of that area has 52-55 dewpoints now. We should be able to get them in the 57-60 degree range by the time the convection really takes off.

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LOT HWO

BUT THERE IS A POSSIBILITY THAT A FEW STORMS COULD BECOME SEVERE TOWARD

LATE AFTERNOON OR EVENING. A LOW PRESSURE SYSTEM PASSING NORTH

OF THE AREA WILL DRAG A COLD FRONT THROUGH OVERNIGHT. INCREASING

INSTABILITY AND LIFT AHEAD OF THE FRONT THIS EVENING...TOGETHER

WITH THE STRONG WIND FIELD ALREADY IN PLACE...COULD SUPPORT

SUPERCELLS WITH LARGER HAIL AND STRONG WIND GUSTS.

Some really nice mid level lapse rates over central IA that should advect that way.

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