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Severe Storm Threat 9/17 - 9/18


Brick Tamland

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mcd1955.gif

DISCUSSION...PRE-FRONTAL ARC OF N/S-ORIENTED CONVECTION HAS

STRUGGLED TO PRODUCE LIGHTNING IN NERN GA INTO THE WRN

CAROLINAS...WITH SOME LIGHTNING OBSERVED IN A CLUSTER ACROSS CNTRL

GA. LOW-LEVEL SHEAR CONTINUES TO INCREASE WITH 0-1 KM VALUES

APPROACHING 35 KT PER AREA VWP DATA. STILL...AMIDST A MEAGERLY

UNSTABLE AIR MASS CHARACTERIZED BY MLCAPE LARGELY AOB 500 J/KG PER

MODIFIED 00Z GSO RAOB AND ONLY MODEST SURFACE PRESSURE FALLS...THIS

ACTIVITY MAY STRUGGLE TO INTENSIFY. BUT A CONDITIONAL TORNADO RISK

DOES EXIST GIVEN THE STRENGTH OF THE LOW-LEVEL SHEAR...AND A

DOWNSTREAM WW ISSUANCE COULD BECOME NECESSARY IF LIGHTNING/ROTATION

TRENDS INCREASE.

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The threat looks minimal for much of the southeast today, with my main concern being damaging winds in the squall line that tries to develop. The low lvl jet will be screaming and some of those winds should mix down to the surface... There's going to be a few rotating storms, but I'd like to see a bit more instability to get a tornado.

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MESOSCALE DISCUSSION 1957

NWS STORM PREDICTION CENTER NORMAN OK

0749 AM CDT TUE SEP 18 2012

AREAS AFFECTED...PORTIONS OF VA/NC TO MD/EASTERN WV/SOUTHERN PA

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 181249Z - 181445Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...SEVERE TSTM POTENTIAL...INCLUDING DAMAGING WINDS AND A FEW

TORNADOES...IS EXPECTED TO STEADILY INCREASE BY LATE MORNING/EARLY

AFTERNOON...INCLUDING PIEDMONT PORTIONS OF NC INTO WESTERN/CENTRAL

VA AND ADJACENT PARTS OF MD/EASTERN WV/SOUTHERN PA. CURRENT THINKING

IS THAT ONE OR MORE WATCHES ARE LIKELY FOR AT LEAST THE MAJORITY OF

THE REGION BY LATE MORNING.

DISCUSSION...AS A POTENT UPPER TROUGH CONTINUES TO SHIFT EASTWARD

OVER THE GREAT LAKES REGION...MID-MORNING SURFACE ANALYSIS FEATURES

A STEADILY DEEPENING SURFACE LOW MOVING INTO WESTERN PA...WITH AMPLE

EARLY DAY PRESSURE FALLS OF 1+ IN/HR NOTED FROM WESTERN PORTIONS OF

VA/MD INTO WESTERN PA/NY. EAST-NORTHEAST OF THIS SURFACE LOW...A

NORTHWARD-ADVANCING WARM FRONT EXTENDS ACROSS PA INTO SOUTHERN NEW

ENGLAND...WHILE A COLD FRONT STRETCHES SOUTH-SOUTHWESTWARD FROM THE

SURFACE LOW NEAR/JUST WEST OF THE APPALACHIANS SPINE INTO GA/AL.

EAST OF THE SURFACE LOW/COLD FRONT...A VERY MOIST AIRMASS IS IN

PLACE ACROSS THE REGION...WITH NEAR 70F SURFACE DEWPOINTS AS FAR

NORTH AS THE DELMARVA VICINITY.

WHILE CONSIDERABLE CLOUD COVER EXISTS ACROSS THE REGION...ALONG WITH

WARM CONVEYOR-DRIVEN SCATTERED PRECIPITATION IN SOME AREAS...GRADUAL

/ALBEIT RELATIVELY MODEST/ DESTABILIZATION IS EXPECTED INTO LATE

MORNING/AFTERNOON AFTERNOON...INITIALLY ACROSS PIEDMONT PORTIONS OF

THE CAROLINAS INTO CENTRAL VA. 12Z OBSERVED SOUNDINGS FROM

WASHINGTON-DULLES AND GREENVILLE-SPARTANBURG SC ARE ALREADY

INDICATIVE OF 500-800 J/KG MLCAPE WITH VIRTUALLY NIL CONVECTIVE

INHIBITION...ALONG WITH A HIGHLY SHEARED/RICH LOW-LEVEL SRH

ENVIRONMENT INCLUDING 0-1 KM SRH OF 250-300 M2/S2. POCKETS OF

STRONGER INSOLATION/HEATING...ALONG WITH A MOIST AIRMASS AND A

STRONG WIND/HIGHLY SHEARED ENVIRONMENT...WILL LIKELY SUPPORT THE

INCREASE/MATURATION OF STRONG/SUSTAINED TSTMS BY LATE

MORNING/MIDDAY...WITH DAMAGING WINDS AND POTENTIAL FOR A FEW

TORNADOES BECOMING A CONCERN.

..GUYER/HART.. 09/18/2012

ATTN...WFO...PHI...AKQ...MHX...CTP...LWX...RAH...ILM...RNK...

CAE...GSP...

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Just read Allan Huffman's latest blog post. He said "that our atmosphere is probably most primed for severe weather over the next few hours with the highest cape, greatest shear and helicity, but we will be lacking a bit in instability. This afternoon, we will be a little more unstable but the dynamics wont be quite as great."

http://www.examiner.com/article/severe-weather-possible-today-5

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And there it is

BULLETIN - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH OUTLINE UPDATE FOR WT 641

NWS STORM PREDICTION CENTER NORMAN OK

945 AM EDT TUE SEP 18 2012

TORNADO WATCH 641 IS IN EFFECT UNTIL 500 PM EDT FOR THE

FOLLOWING LOCATIONS

NCC001-037-051-063-065-069-077-083-085-093-101-105-125-127-135-

145-153-163-165-181-183-185-191-195-182100-

/O.NEW.KWNS.TO.A.0641.120918T1345Z-120918T2100Z/

NC

. NORTH CAROLINA COUNTIES INCLUDED ARE

ALAMANCE CHATHAM CUMBERLAND

DURHAM EDGECOMBE FRANKLIN

GRANVILLE HALIFAX HARNETT

HOKE JOHNSTON LEE

MOORE NASH ORANGE

PERSON RICHMOND SAMPSON

SCOTLAND VANCE WAKE

WARREN WAYNE WILSON

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Let's not have any snowstorm2011 posts in here.

True....didn't mean to sound whiny , but being in Vancouver, it's tough for you to imagine what it's like down here with hardly any precip going on a year and a half now, especially coupled with all the SPC risk areas we've had. :arrowhead: Please send some precip down here this fall!

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mcd1960.gif

MESOSCALE DISCUSSION 1960

NWS STORM PREDICTION CENTER NORMAN OK

1019 AM CDT TUE SEP 18 2012

AREAS AFFECTED...FAR NRN SC...CNTRL/ERN NC...CNTRL/ERN VA...DISTRICT

OF COLUMBIA...CNTRL/ERN MD...MUCH OF DE...ERN PA...WRN/NRN

NJ...PARTS OF ERN NY

CONCERNING...OUTLOOK UPGRADE

VALID 181519Z - 181645Z

SUMMARY...A CATEGORICAL UPGRADE TO MODERATE RISK IS PLANNED FOR THE

UPCOMING 1630 UTC DAY-1 CONVECTIVE OUTLOOK FROM PARTS OF THE

CAROLINAS NWD INTO PARTS OF ERN NY.

DISCUSSION...STRONG LOW-LEVEL AND DEEP SHEAR IN ASSOCIATION WITH A

CONUS-FULL-LATITUDE TROUGH WILL SUPPORT MULTIPLE QLCS SEGMENTS

ACROSS A BROAD WARM SECTOR OVER THE ERN CONUS. WIDESPREAD SVR WIND

GUSTS WILL BE THE MAIN CONCERN ACROSS THE UPCOMING MODERATE RISK

AREA...AND SVR WIND PROBABILITIES WILL BE INCREASED TO 45 PERCENT

ACROSS THIS REGION. HOWEVER...TORNADOES WILL ALSO BE

POSSIBLE...PARTICULARLY WITH EMBEDDED LEWP STRUCTURES...LINE

BREAKS...AND DISCRETE CONVECTION EVOLVING AHEAD AN APPROACHING

EXTENSIVE COLD FRONT. PLEASE SEE THE FORTHCOMING OUTLOOK FOR

ADDITIONAL METEOROLOGICAL INFORMATION.

..COHEN/CARBIN/MEAD.. 09/18/2012

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I was just going to say all that I have had here at work in RTP is some rain. There have been some severe storm warnings around, but nothing extreme. However, the sun is starting to come out now. I thought maybe it meant things were not going to be as bad as previously thought, but then I just saw the discussion up there. Maybe the sun will heat things up and create more instability. I thought the threat was bigger this morning around here for severe weather and tornadoes, but I guess it continues.

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SPECIAL WEATHER STATEMENT

NATIONAL WEATHER SERVICE RALEIGH NC

1203 PM EDT TUE SEP 18 2012

NCZ007-008-024-025-181700-

DURHAM-GRANVILLE-ORANGE-PERSON-

1203 PM EDT TUE SEP 18 2012

...A STRONG THUNDERSTORM WILL MOVE ACROSS PERSON...ORANGE...GRANVILLE

AND DURHAM COUNTIES THROUGH 100 PM EDT...

AT 1203 PM EDT...DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER

SCHLEY...OR ABOUT OVER HILLSBOROUGH...MOVING NORTHEAST AT 40 MPH.

SOME LOCATIONS AFFECTED BY THIS STORM INCLUDE...ROUGEMONT...AND...

BAHAMA...SURL...AND...MORIAH...BEREA...OAK HILL...STOVALL...KERR

LAKE.

HAZARDS INCLUDE...

GUSTY WINDS OF 40 TO 50 MPH.

SEEK SHELTER IN A NEARBY BUILDING OR VEHICLE. STRONG WINDS ARE

CAPABLE OF KNOCKING DOWN SMALL TREES AND BLOWING AROUND TRASH CANS...

POTTED PLANTS...LAWN FURNITURE AND OTHER LIGHT OUTDOOR OBJECTS.

A TORNADO WATCH REMAINS IN EFFECT UNTIL 500 PM EDT TUESDAY AFTERNOON

FOR CENTRAL NORTH CAROLINA.

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Man, the southeast forum seems dead. They are on page 6 in the NYC Metro forum talking about this severe weather possibility, and nothing has even happened up there yet.

NY Metro is in the 10% tornado probability...we're in the 5% majority of the SE is in the 2%, they hardly ever see severe weather as far as tornadoes, so this is more exciting to them. We've seen threats with 2-5% probability of tornadoes in the middle of tornado season and it never comes to fruition so I'm thinking most posters and mets think this is not a big deal, which it shouldn't be when it finally plays out. We're in the middle of September....NYC has more daylight hours to get the heating too, as the system will come later...several reasons why they're hyped and we're dead.

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URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 644

NWS STORM PREDICTION CENTER NORMAN OK

1230 PM EDT TUE SEP 18 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF

EASTERN NORTH CAROLINA

COASTAL WATERS

EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 1230 PM UNTIL

800 PM EDT.

SEVERAL TORNADOES

SCATTERED DAMAGING WINDS

ISOLATED WIND GUSTS TO 70 MPH POSSIBLE

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE

MILES EAST AND WEST OF A LINE FROM 20 MILES NORTH NORTHWEST OF

ELIZABETH CITY NORTH CAROLINA TO 25 MILES EAST SOUTHEAST OF

JACKSONVILLE NORTH CAROLINA. FOR A COMPLETE DEPICTION OF THE

WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).

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 641...WW 642...WW 643...

DISCUSSION...DAYTIME HEATING COUPLED WITH A VERY MOIST ENVIRONMENT

HAS RESULTED IN A MODERATELY UNSTABLE AIR MASS WITH MLCAPE OF

1000-1500 J/KG. CURRENT MHX VAD SHOWS A VERTICALLY VEERING WIND

PROFILE WITH SUFFICIENT LOW AND DEEP-LAYER SHEAR FOR ORGANIZED STORM

MODES INCLUDING SUPERCELLS AND BOWING LINE SEGMENTS. WHILE DAMAGING

WINDS WILL BE THE PRIMARY HAZARD...A FEW TORNADOES ARE ALSO

POSSIBLE.

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

SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE

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

450. MEAN STORM MOTION VECTOR 23035.

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Yeah I mean it's looking like the Raleigh metro area for some real action and rain for everyone else. We've had a few squalls move through in the Triad with some decent wind but nothing very exciting. I did notice it broke one of my bird feeders...maybe I should call it in?

Also, my other excuse is I've been in PR way too much lately. I could use some interesting weather.

edit: As soon as I post this the bottom drops out. Most intense storm of the day so far.

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