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April 26th Severe Weather


Chicago Storm

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MESOSCALE DISCUSSION 0592

NWS STORM PREDICTION CENTER NORMAN OK

0301 PM CDT TUE APR 26 2011

AREAS AFFECTED...EAST-CENTRAL/SOUTH-CENTRAL TX AND TX HILL COUNTRY

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 262001Z - 262130Z

MONITORING DEVELOPMENTAL TRENDS FOR THE POSSIBILITY OF A TORNADO

WATCH ACROSS PORTIONS OF SOUTH-CENTRAL/EAST-CENTRAL TX AND THE TX

HILL COUNTRY.

VISIBLE SATELLITE IMAGERY REFLECTS AN INCREASING/DEEPENING CU FIELD

IN VICINITY OF A SOUTH-CENTRAL TX/HILL COUNTRY DRYLINE. THE EXACT

COVERAGE OF EVENTUAL DEEP CONVECTION IS A BIT UNCERTAIN WITH

SOUTHWARD EXTENT GIVEN THE PRESENCE OF A STRONG EML...BUT AT LEAST

MODEST HEIGHT FALLS/UPPER FORCING IS EXPECTED TO GRAZE THE REGION.

ALONG THESE LINES...AN ASSORTMENT OF NUMERICAL GUIDANCE...SUCH AS

THE 12Z ECMWF AND VARIOUS 15Z SREF MEMBERSHIP...IMPLY THE

POSSIBILITY OF AT LEAST ISOLATED DEEP CONVECTIVE DEVELOPMENT AS FAR

SOUTH AS THE AUSTIN-SAN ANTONIO AREAS AND ADJACENT HILL COUNTRY.

WHERE SURFACE BASED DEVELOPMENT DOES OCCUR...VERY STEEP LAPSE RATES

AND STRONG INSTABILITY /3000-4000 J PER KG MLCAPE/ COUPLED WITH

STRONG/VEERING WIND PROFILES WILL BE MORE THAN ADEQUATE FOR

SUPERCELLS CAPABLE OF LARGE HAIL AND SOME TORNADOES.

..GUYER.. 04/26/2011

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868

WWUS20 KWNS 262004

SEL7

SPC WW 262004

ARZ000-ILZ000-KYZ000-MOZ000-MSZ000-TNZ000-270300-

URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 217

NWS STORM PREDICTION CENTER NORMAN OK

305 PM CDT TUE APR 26 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF

EASTERN ARKANSAS

SOUTHEAST ILLINOIS

WESTERN KENTUCKY

SOUTHEAST MISSOURI INCLUDING THE BOOTHEEL

NORTHWEST MISSISSIPPI

WEST TENNESSEE

EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 305 PM UNTIL

1000 PM CDT.

..THIS IS A PARTICULARLY DANGEROUS SITUATION

DESTRUCTIVE TORNADOES...LARGE HAIL TO 2.5 INCHES IN DIAMETER...

THUNDERSTORM WIND GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE

POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE

MILES EAST AND WEST OF A LINE FROM 75 MILES NORTH OF FORT

CAMPBELL KENTUCKY TO 35 MILES EAST OF EL DORADO ARKANSAS. FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU7).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION...CONTINUE...WW 213...WW 214...WW

215...WW 216...

DISCUSSION...THUNDERSTORMS ARE INTENSIFYING ALONG A WEAK SURFACE

BOUNDARY EXTENDING FROM CENTRAL AR INTO WESTERN KY. A FEW OF THESE

INITIAL STORMS WILL LIKELY BECOME SUPERCELLS WITH A RISK OF LARGE

HAIL...DAMAGING WINDS...AND ISOLATED TORNADOES. THE RISK OF

SIGNIFICANT SEVERE WEATHER WILL INCREASE THROUGH THE EVENING AS

STORMS FORM TO THE SOUTHWEST AND MOVE INTO THE WATCH AREA. VERY

STRONG SHEAR PROFILES DURING THE LATTER HALF OF THE WATCH PERIOD

SUGGEST THAT PDS WORDING IS APPROPRIATE...WITH STRONG TORNADOES

POSSIBLE.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

500. MEAN STORM MOTION VECTOR 24035.

...HART

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Pretty incredible range of parameters out there and hard to find something against this tornado outbreak. I remember last year when something like this was expected over Arkansas but all the supercells had a tough time producing touchdowns. I remember Attica and me were speculating on why and I brought up the insane anvil level winds. He argued that because the supercells were out ahead of the surface boundary that the anvil level winds may not have been detrimental. The local WFOs were talking about the weaker than expected juxtaposition of the CAPE and shear parameters but that clearly wasn't lining up with the obs.

Anyway, the point is...the current anvil level winds are exceeding 50kts along the warm front and max out over 70kts.

I didn't participate in that discussion and don't recall the setup, but I know two big mistakes I see a lot of folks make (not saying here, but in general) is not realizing that you can have too much shear for the instability, and ignoring LCL / LFC heights that may be too high and make it tougher for a touchdown. Too often I have seen people look only at CAPE and helicity and make a forecast.

Anyhow, not sure either of those will limit this one (the LCL / LFC heights won't). The BRNs were on the low side of the scale on the northern edge of the instability though.

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BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE FORT WORTH TX

328 PM CDT TUE APR 26 2011

THE NATIONAL WEATHER SERVICE IN FORT WORTH HAS ISSUED A

* TORNADO WARNING FOR...

SOUTHERN ELLIS COUNTY IN NORTH CENTRAL TEXAS...

NORTHWESTERN NAVARRO COUNTY IN NORTH CENTRAL TEXAS...

* UNTIL 415 PM CDT

* AT 328 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A

DEVELOPING TORNADO 7 MILES NORTHWEST OF MILFORD...MOVING EAST AT 25

MPH.

* THE TORNADO WILL BE NEAR...

ITALY AROUND 340 PM CDT...

BARDWELL AROUND 410 PM CDT...

ENNIS...GARRETT AND ALMA AROUND 415 PM CDT...

THIS WILL IMPACT THE FOLLOWING INTERSTATES...

I-35E BETWEEN MILE MARKERS 9 AND 27...

I-45 BETWEEN MILE MARKERS 243 AND 256.

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SEVERE WEATHER STATEMENT

NATIONAL WEATHER SERVICE BINGHAMTON NY

429 PM EDT TUE APR 26 2011

NYC065-262045-

/O.CON.KBGM.TO.W.0001.000000T0000Z-110426T2045Z/

ONEIDA NY-

429 PM EDT TUE APR 26 2011

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 445 PM EDT FOR CENTRAL

ONEIDA COUNTY...

AT 425 PM EDT...TRAINED WEATHER SPOTTERS REPORTED A TORNADO. THIS

TORNADO WAS LOCATED NEAR ROME...MOVING NORTHEAST AT 40 MPH.

THE TORNADO WILL BE NEAR...

STEUBEN AND HOLLAND PATENT BY 440 PM EDT...

WESTERNVILLE AND FLOYD BY 435 PM EDT...

FRENCHVILLE...NORTH WESTERN AND STITTVILLE BY 440 PM EDT...

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