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Severe storms 2015 general chatter

Ian

By Ian,
in Mid Atlantic

Corn fuel  

64 members have voted

  1. 1. When will DCA report its first spring thunder?

  2. 2. How many days with severe weather watches in the subforum in 2015?


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Kmlwx

Kmlwx

Posted
Posted

I don't think we have seen numbers like that around here... pretty interesting.  Yes, I know the threat is tempered by low instability and poor LR... but still looks pretty decent

Latest run toned things back a good bit. Also puts emphasis on south threat. Timing looks to have shifted up a decent amount too on potential storms. Might get some scattered stuff 22-00z and then a weak line later maybe. 

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yoda

yoda

Posted
Posted

09z SREF run on the SPC site is a bit less impressive and also just like the HRRR shifts the threat to around 00z perhaps with the best parameters. 

 

I think it was high risk who mentioned it in his post yesterday, but it would appear the best chance for any "severe" would be between 23z and 05z IMO... believe high risk posted 00z to 04z

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high risk

high risk

Posted
Posted

   yes, I had been thinking 00-04z with a severe threat in a band just ahead of the front, but as the models have now started to converge on the timing, I think I have to modify things a bit.  Based on several consecutive runs of the HRRR, there may be two distinct threats here:

 

    1)   The HRRR has a wide band of heavy rain moving through the area between roughly 6 and 8PM.   It's probably mostly just lots of rain, but it's in an environment with good shear and some instability.   The 13z HRRR reflectivity prog looks somewhat cellular, and I saw a nice updraft helicity track in the 12z cycle along with a modest lightning signal.   

 

    2)   Then after a break, the front approaches around midnight or so, and the HRRR at the end of its run has a band approaching with a surge of cape ahead of it.   I thought this would be the player, and it still might, but the best forcing may be just north of our area.

 

I think it was high risk who mentioned it in his post yesterday, but it would appear the best chance for any "severe" would be between 23z and 05z IMO... believe high risk posted 00z to 04z

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yoda

yoda

Posted
Posted

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1017 AM EDT WED OCT 28 2015

.SYNOPSIS...
LOW PRESSURE WILL TRACK NORTH ACROSS THE UPPER MIDWEST TODAY. THE
LOW WILL LIFT A WARM FRONT THROUGH THE MID-ATLANTIC TODAY FOLLOWED
BY A COLD FRONT TONIGHT. ANOTHER COLD FRONT WILL CROSS THE REGION
THURSDAY. HIGH PRESSURE RETURNS FRIDAY AND SATURDAY. A WARM FRONT
WILL FORM OVER NORTH CAROLINA SUNDAY AND SLOWLY TRACK NORTH.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...PRECIP TURNING MORE SHOWERY
THIS MORNING ALTHOUGH WARM FRONT IS STILL OVER COASTAL VA AND NC.
GUIDANCE SUGGESTS STRONG PRESSURE FALLS WILL OCCUR THROUGH THE DAY
AND VERY STRONG SRLY WINDS JUST OFF THE SURFACE MAKES IT LIKELY
THAT THE WARM FRONT WILL LIFT NORTH THROUGH THE AREA AT SOME POINT
IN THE AFTERNOON. VERY LITTLE IF ANY BREAKS IN CLOUD COVER
EXPECTED BUT STRONG WARM AIR ADVECTION WILL BOOST TEMPS CLOSE TO
70F IF NOT HIGHER. NCAR 3-KM 10-MEMBER WRF ARW ENSEMBLE AND LATEST
GFS SUGGEST A LINE OF LOW-TOPPED CONVECTION WILL MOVE THROUGH THE
AREA EITHER LATE AFTERNOON OR EARLY EVENING. STRONG WINDS JUST OFF
THE SFC AND 0-6KM MEAN FLOW OF 50-KT INDICATE POTENTIAL FOR FAST
MOVING LINE OF CONVECTION WITH SEVERE WIND GUSTS EVEN IF NO
T-STORMS DEVELOP. PRECIP SHOULD END AROUND 06Z WITH FROPA.

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high risk

high risk

Posted
Posted

     I think we're starting to see consensus on this.    Between a lot of HRRRs, the newest NAM nest, last night's hi-res windows, the LWX hi-res run, and the NCAR ensemble, they point to the 22-01z timeframe for a batch of heavy rain approaching from the south-southwest, possibly with some embedded thunderstorms.  This is probably our best chance for an embedded rotational cell, but the chances may not be too great.    The 04-05z threat along the front is still there, but some the guidance really downplays this now.

 

 


LWX WRF-ARW likes the two batch idea - one around 23z and then a bit of a weaker looking thing after 03z. 

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Kmlwx

Kmlwx

Posted
Posted

     I think we're starting to see consensus on this.    Between a lot of HRRRs, the newest NAM nest, last night's hi-res windows, the LWX hi-res run, and the NCAR ensemble, they point to the 22-01z timeframe for a batch of heavy rain approaching from the south-southwest, possibly with some embedded thunderstorms.  This is probably our best chance for an embedded rotational cell, but the chances may not be too great.    The 04-05z threat along the front is still there, but some the guidance really downplays this now.

This all seems pretty standard for our area - stuff likes to get in a lot earlier than progged a few days out. We'll see if anything interesting other than heavy rain forms. 

Gusty showers is still my call ;) 

FYI - your posts are always super complete and informative - thank you!

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high risk

high risk

Posted
Posted

   you forgot  "and spectacularly wrong".    but you are too kind - thanks!

 

   With this event, the problem is two-fold:   there is some sort of lead shortwave (not totally sure - haven't looked closely enough) that is going to fire widespread showers (and maybe TRW) in the very early evening, and then the front is actually slower than it had looked.   The mid-level cooling will help the cape a lot, but that only slowly arrives during the evening.  Without that lead wave and a slightly faster front, we could have had a nice window in the late evening for a strong line.  Instead, the 22-00z stuff is the main show, with lesser threat of a line along the front at 1AM.    Overall, that 22-00z threat will have crummy lapse rates and overall limited instability, so the severe threat is low.   That said, there is strong shear and *some* cape, and the HRRR has a nice lightning signal, so it has to be watched.   Hell, I got the weak EFO go through my backyard a few weeks ago in an event with strong shear, very little cape, and no lightning.

 

This all seems pretty standard for our area - stuff likes to get in a lot earlier than progged a few days out. We'll see if anything interesting other than heavy rain forms. 

Gusty showers is still my call ;) 

FYI - your posts are always super complete and informative - thank you!

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yoda

yoda

Posted
Posted

1630 OTLK from SPC

 


..ERN/SERN/MID-ATLANTIC STATES TODAY THROUGH EARLY TNGT    AMPLE MOISTURE AND LOW-LVL SHEAR WILL BE PRESENT ACROSS A LARGE PART  OF THE E CNTRL U.S. THIS AFTN AND EVE TO POSE AT LEAST A CONDITIONAL  RISK FOR LOCALLY SVR STORMS WITHIN BROAD REGIME OF LOW-LVL CYCLONIC  FLOW. THIS POTENTIAL APPEARS GREATEST OVER /1/ PARTS OF THE UPR OH  VLY AND ALONG THE WRN SLOPES OF THE APPALACHIANS...AND /2/ OVER  PARTS OF THE SOUTHEAST AND MID-ATLANTIC.    MODEST SFC HEATING AND PERSISTENT LOW-LVL UPLIFT ALONG UPR OH VLY  CONFLUENCE ZONE MAY SUPPORT SCTD AFTN SHOWERS/ISOLD STORMS IN  ENVIRONMENT OF VERY STRONG LOW-LVL SHEAR/FLOW FROM WV NNE INTO FAR  ERN OH/WRN PA...WHERE PW WILL BE AROUND 1.25 INCHES. SOME DEGREE OF  UPR-LVL SUPPORT ALSO MAY BE PROVIDED BY DEAMPLIFYING UPR IMPULSE NOW  MOVING NNE ACROSS OH/LWR MI. LOW TO MID-LVL LAPSE RATES  WILL...HOWEVER...REMAIN VERY WEAK...AND A SHALLOW STABLE LAYER  LIKELY WILL LINGER OVER MOST AREAS AT THE SFC. THUS...AN UPGRADE TO  SLIGHT RISK DOES NOT APPEAR WARRANTED ATTM. THE SVR THREATS WOULD BE  LIMITED TO A BRIEF TORNADO AND/OR LOCALLY DMGG WIND.    FARTHER S/SE...MORE SUBSTANTIAL MOISTURE /PW AOA 1.50 INCHES WITH  DEWPOINTS WELL INTO THE 60S F/ WILL PREVAIL FROM THE CAROLINAS NEWD  INTO SE PA/NJ...ALONG AND S OF SLOWLY ADVANCING WARM FRONTAL  SEGMENTS. WINDS WILL GRADUALLY DIMINISH WITH TIME AND SRN  EXTENT...BUT WILL REMAIN SUFFICIENT FOR ORGANIZED/SUSTAINED STORMS.  AND...AMPLE LOW-LVL DIRECTIONAL SHEAR WILL EXIST NEAR SHALLOW WARM  FRONT TO SUPPORT LOW-LVL MESOS AND A RISK FOR TORNADOES. SATELLITE  AND MORNING RAOB DATA SUGGEST...HOWEVER...THAT MOST OF THE REGION SW  OF ABOUT RALEIGH NC WILL BE IN A ZONE OF RELATIVE NVA THROUGH THE  DAY...ALTHOUGH LIMITED DCVA WILL LINGER FARTHER N AND E INTO THE  CHESAPEAKE BAY REGION/SE PA-NJ. AT THE SAME TIME...MID-LVL LAPSE  RATES WILL BE WEAK...WITH FURTHER 500 MB WARMING EXPECTED ACROSS  MUCH OF THE CAROLINAS AND VA. THE OVERALL SET-UP APPEARS TO BE ONE  WITH A FAIRLY EXPANSIVE BUT LOW-CONDITIONAL THREAT FOR BRIEF  TORNADOES. THIS THREAT DOES NOT APPEAR TO BE OF SUFFICIENT MAGNITUDE  OR FOCUS...HOWEVER...TO WARRANT AN UPGRADE OF SLIGHT RISK ATTM.  
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Kmlwx

Kmlwx

Posted
Posted

I feel like sometimes SPC gives our area some of the most detailed and informative discussions when the threat is pretty marginal. Maybe it's just an illusion or poor memory but i feel like during some "decent" potential events they just use a cookie cutter discussion. That is a really detailed/comprehensive discussion right there. 

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