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November 16th-18th Storm General Discussion/Obs


Geos

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From CLE's HWO:
 

THE STORM PREDICTION CENTER HAS INDICATED THAT THERE IS A
MODERATE RISK FOR SEVERE THUNDERSTORMS ON SUNDAY AFTERNOON AND
EVENING. A SQUALL LINE IS EXPECTED TO DEVELOP AND MOVE ACROSS THE
LOCAL AREA LATE SUNDAY AND SUNDAY EVENING. VERY STRONG WINDS ARE
EXPECTED JUST OFF THE SURFACE. HEAVY RAIN FROM THE SQUALL LINE
COULD BRING THESE STRONG WINDS DOWN TO THE SURFACE CAUSING
WIDESPREAD DAMAGE. THIS IS VERY DANGEROUS SITUATION.
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Chicago nws discussion

THINGS REALLY BEGIN TO GET POTENTIALLY INTERESTING ON SUNDAY AS

STRONG SHORTWAVE BEGINS TO TAKE ON A MORE NEUTRAL AND EVENTUALLY

NEGATIVE TILT BY EVENING AS IT TRACKS INTO THE GREAT LAKES.

INGREDIENTS REALLY SEEM TO BE FALLING VERY NICELY INTO PLACE FOR A

SEVERE THUNDERSTORMS WITH A DAMAGING WIND AND TORNADO THREAT SUNDAY

ACROSS OUR CWA. POWERFUL 120KT+ UPPER JET IS PROGGED TO NOSE INTO

CENTRAL ILLINOIS BY 18Z SUNDAY WITH STRONG UPPER LEVEL DIVERGENCE IN

THE LEFT EXIT REGION OF THE JET LIKELY SUPPORTING STRONG LARGE SCALE

ASCENT OVER THE AREA WITH RAPIDLY DEEPENING SURFACE LOW AND STRONG

SURGING COLD FRONT LIKELY TO PROVIDE THE STRONGEST LOW LEVEL

FORCING/FOCUS FOR CONVECTIVE INITIATION SUNDAY ALONG THE FRONT.

COLD SEASON SEVERE WEATHER IN OUR AREA OFTEN FEATURE SBCAPE OF LESS

THAN 1000 J/KG...YET GUIDANCE CONTINUE TO ADVERTISE SBCAPES

APPROACHING 1500 J/KG SUNDAY AFTERNOON AS POCKET OF VERY COLD AIR

ALOFT MOVES IN WITH 700-500MB LAPSE RATES >8C/KM. THE INSTABILITY

COMBINED WITH THE TYPICALLY STRONG/EXTREME SHEAR WITH DEEP COLD

SEASON CYCLONE RAISES THE THREAT OF A POTENTIALLY DANGEROUS SEVERE

WEATHER EPISODE ACROSS THE REGION. MODEL FORECASTS SUGGEST THAT

THERE WILL BE A FAIRLY BROAD WARM SECTOR SUNDAY AFTERNOON WITH

MODERATE INSTABILITY AND MINIMAL CINH. CERTAINLY THE MOST LIKELY

SCENARIO WOULD BE FOR CONVECTION TO BE FOCUSED ALONG THE COLD FRONT

AND LIKELY GOING LINEAR FAIRLY QUICKLY AFTER INITIATION...BUT WITH

THE POTENTIAL FOR A DEVELOPING LARGE STRONGLY SHEARED AND WEAKLY

CAPPED WARM SECTOR CANNOT RULE OUT SUPERCELLS DEVELOPING AHEAD OF

CONVECTIVE LINE DUE TO LARGE SCALE ASCENT IN LEFT EXIT REGION OF JET

COUPLED WITH MODEST LOW LEVEL THETA-E ADVECTION. INITIAL DEVELOPMENT

OF CONVECTION ALONG THE COLD FRONT COULD ALSO BE SUPERCELLS

BEFORE MORPHING INTO A LINE...IN EITHER OF THESE SCENARIOS POTENTIAL

WOULD EXIST FOR TORNADIC SUPERCELLS. CLIMO SUGGESTS THAT NOVEMBER

TORNADOES IN OUR AREA ARE VERY RARE...BUT WHEN THEY OCCUR THEY ARE

FREQUENTLY STRONG. DAMAGING WIND THREAT WITH CONVECTIVE LINE LOOKS

TO BE QUITE HIGH GIVEN THE ALREADY STRONG FIELDS IN PLACE...WITH

ATTENDANT THREAT OF EMBEDDED MESOVORTEX DEVELOPMENT LEADING TO

ENHANCED WIND DAMAGE AND/OR QLCS TORNADO THREAT.

DEFINITELY WORTH NOTING THAT THERE ARE MANY MESOSCALE VARIABLE THAT

NEED TO FALL INTO PLACE JUST RIGHT TO RESULT IN SIGNIFICANT SEVERE

WEATHER OUTBREAKS. ITS CERTAINLY NOT HARD TO ENVISION MULTIPLE

SCENARIOS WHERE OUR CWA DODGES ANOTHER SEVERE WEATHER BULLET...BUT

CURRENT INDICATIONS ARE THAT A SIGNIFICANT TORNADO/DAMAGING WIND

THREAT COULD DEVELOP SUNDAY EITHER IN OR CLOSE TO OUR AREA. DESPITE

THE UNCERTAINTIES AND BUST POTENTIAL...ENOUGH INGREDIENTS APPEAR TO

BE FALLING INTO PLACE TO REALLY RATCHET UP THE "HYPE" FOR THE

POTENTIAL EVENT. A COUPLE OF THINGS TO CONSIDER ABOUT THIS EVENT IS

THAT IT WOULD BE AN "OUT OF SEASON" EVENT ON THE WEEKEND WHICH COULD

CATCH PEOPLE OFF GUARD. IN ADDITION...THE VERY STRONG WIND FIELDS

WILL RESULT IN AN EXTREMELY FAST WITH BUNKERS FORECAST RIGHT MOVING

STORM MOTION SUGGESTING THE POTENTIAL FOR STORMS TO BE MOVING AT

CLOSE TO 60KT.

IN ADDITION TO THE CONVECTIVE THREAT...VERY STRONG PRESSURE FALLS IN

ADVANCE OF THE LOW AND TIGHTENING PRESSURE GRADIENT LOOKS TO RESULT

IN SYNOPTIC WINDS REACHING ADVISORY CRITERIA FOR MUCH OF THE CWA

SUNDAY AND WILL BE HOISTING A WIND ADVISORY.

IZZI

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I'm in Davison, MI through Tue AM...this is my best severe setup in a long time. :lol:

 

Up there in the Flint area seems to be a hot spot for severe weather locally. One of Michigan's very rare F5s hit in that area (Flint-Beecher) one June back in the 1950s. 

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Guys...so we're on the same page as we head into tomorrow...the pinned severe thread in the main forum is meant to be the primary severe thread for this event.  Some severe chit chat in here is not an issue but there's a point where disco becomes too fragmented.  Models/watches/warnings/analysis/discussions etc should primarily be in the main thread.      

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Pretty much calmed down now, but that was quite a storm. Horizontal rain blowing in sheets. Best one since September no doubt.

Pushing 0.25" rain today.

 

Any ventured guesses when the severe weather threat is highest in IL tomorrow?

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Latest guidance indicating a small area of very strong winds immediately behind the low track over eastern Iowa tomorrow afternoon.  RAP sounding from near Muscatine shows surface winds sustained at 35kts!  Winds just off the deck at over 55kts.  Could be a brief window for high wind warning criteria tomorrow late morning into the afternoon for this feature.  Wouldn't be at all surprised to see 55mph+ gust associated with this feature.  Model soundings show deep mixing behind the front as well, along with strong subsidence. 

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Here's a graphic from the 01z RAP showing some of the wind potential following the bombing cyclone I had mentioned awhile ago.  Who knows how accurate this is, but it shows where some very strong winds could occur with the pressure rise/fall couplet.  Note there's a small 60kt lollipop in there lol.

 

gust_t210m_f18.png

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you get those icicle lights up yet Geos? ....

 

via LOT...

 

 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
937 PM CST SAT NOV 16 2013

.DISCUSSION...
937 PM CST

THERE ARE SEVERAL WEATHER CONCERNS OVER THE NEXT 20 HOURS ASSOCIATED
WITH THE MAJOR AUTUMN STORM SYSTEM EXPECTED TO TRACK NORTHEASTWARD
FROM THE MID-MISSOURI VALLEY ACROSS WISCONSIN AND THE UPPER GREAT
LAKES REGION BY EARLY SUNDAY EVENING.

NOT MUCH HAS CHANGED IN REGARDS TO THE SEVERE THREAT ON SUNDAY. THE
ONLY CHANGES TO THE GOING FORECAST WAS TO EXPAND THE WIND
ADVISORY FOR THE REMAINDER OF NORTHERN ILLINOIS FOR SUNDAY. I AM
CONCERNED THAT WE COULD SEE A BRIEF PERIOD OF WIND GUSTS UP AROUND
55 TO POSSIBLY 60 MPH WITH THE FRONTAL PASSAGE LATER IN THE
AFTERNOON.
WITH THE TRACK OF THIS RAPIDLY DEEPENING AND FAST
MOVING LOW JUST NORTH OF THE AREA ACROSS SOUTHERN WISCONSIN...THIS
WILL PLACE NORTHERN ILLINOIS/NORTHWESTERN INDIANA IN THE PRIME
AREA FOR STRONG WINDS OUTSIDE OF THUNDERSTORMS. STRONG ISALLOBARIC
PRESSURE RISES OF 12 TO 15 MB ARE FORECAST WITHIN ONLY A 6 HOUR
PERIOD ACROSS NORTHERN ILLINOIS IN THE WAKE OF THE FRONTAL ZONE.
THIS COMBINED WITH AROUND 50 KT OF FLOW EXPECTED WITHIN A COUPLE
THOUSAND FEET OF THE SURFACE...COULD RESULT IN THIS SHORT PERIOD
OF VERY STRONG WIND GUSTS.
 

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That's going to be interesting. Yeah I've got most of the outside lights up now. Hopefully I won't have to rearrange any tomorrow!

 

my neighbor to the north has yet to rake one leaf yet.....hopefully the south winds will blow them far away before the front rolls in to blow them onto my lawn lol....

 

hey, this system has a shot at the top 5 for LP's in the great lakes???  (in terms of lowest pressures) .... not too shabby

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