Jump to content

  • Member Statistics

    17,588
    Total Members
    7,904
    Most Online
    LopezElliana
    Newest Member
    LopezElliana
    Joined

2013 Mid-Atlantic Severe General Discussion

Kmlwx

By Kmlwx,
in Mid Atlantic

Recommended Posts

  • Replies 1.2k
  • Created
  • Last Reply
thunderman

thunderman

Posted
Posted

Remember guys, supercells generate their own omega to some extent.  You don't need 2000 j/kg of CAPE.  If you can get a little instability going at surface to touch things off (i.e. a little sun OR theta convection) you can get supercells.

Given the clearing to the southwest and the fact that guidance has sufficient instability verbatim, it is far to early to be writing this one off.

Link to comment
Share on other sites
yoda

yoda

Posted
Posted

Updated LWX AFD as of 11 AM (just posting svr wthr risk part)... seems like the modified sounding showed a bit more instability:

 

 

 

DESPITE LIMITED DAYTIME DESTABILIZATION WITH GENERALLY MINIMAL
BREAKS IN THE CLOUD COVER...12Z IAD MODIFIED SOUNDING SHOWS SBCAPE
AROUND 1000 J/KG AS DEWPOINTS INCREASE TO THE LOW 70S SOUTH OF THE
BOUNDARY. GIVEN LOCATION OF THE WARM FRONT AND LATEST VIS SAT
SHOWING SOME CLEARING NEAR THE VA-NC BORDER...SOME BREAKS IN THE
CLOUD COVER MAY DEVELOP THIS AFTN ESPECIALLY OVER PORTIONS OF
CENTRAL VA AND SRN MD...WHICH WOULD ALLOW FOR POCKETS OF HIGHER
INSTABILITY WITH SBCAPE GREATER THAN 1500 J/KG. EVEN IF
INSTABILITY REMAINS WEAK...AFOREMENTIONED SOUTHERLY LLVL JET WILL
ENHANCE SHEAR AND THIS MAY COMPENSATE FOR A LIMITATION IN
INSTABILITY. THUS...SOME STORMS MAY BECOME SEVERE PRODUCING
DAMAGING WIND GUSTS. AND GIVEN FORECAST SHEAR/HODOGRAPH
CONSIDERATIONS CAN NOT RULE OUT THE RISK FOR ISOLATED TORNADOES
ESPECIALLY IN AREAS THAT WIND UP HAVING HIGHER INSTABILITY AND SFC
WINDS CAN REMAIN BACKED MORE OUT OF THE SE.
Link to comment
Share on other sites
yoda

yoda

Posted
Posted

If we are to accept them as correct, 12z NAM showing some nice curved hodo's from 18z on till around 03z at KIAD... 03z has a "loop de loop" hodo... SBCAPE is around 1100 J/KG with really low (and I mean REALLY LOW) LCL heights - as in below 185m at 18z and 21z

 

About the same at DCA... 0-1 km shear is nice, SRH at both levels 200+... 0-6 km shear is decent around 30-35 kts

 

FWIW, 00z GFS also looked decent for the area as well looking at soundings

Link to comment
Share on other sites
wxmeddler

wxmeddler

Posted
Posted

 

39N 77W? That's almost right over DC. Pretty astounding if it comes to fruition, which it likely won't. #stupidNAM

 

Re Today: Watch the first 10 miles of the western shore of the bay in AA and Balt counties. This is the kind of day that low level helicity can jump dramatically from the enhanced SE winds coming up the rivers. Kind of a theory of mine that started when the F1 went through the next street down in 2006.

Link to comment
Share on other sites
Ian

Ian

Posted
Posted

39N 77W? That's almost right over DC. Pretty astounding if it comes to fruition, which it likely won't. #stupidNAM

 

Re Today: Watch the first 10 miles of the western shore of the bay in AA and Balt counties. This is the kind of day that low level helicity can jump dramatically from the enhanced SE winds coming up the rivers. Kind of a theory of mine that started when the F1 went through the next street down in 2006.

 

nam pretty ideal for thurs.. maybe a smidge fast as the profile has westerly winds by 0z tho i guess most of our tornado events are mid afternoon around here.  has a nice lee low etc.  hard to trust tho i think that period (wed-thur) is our best shot this year if it holds as it looks on the models. 

 

wed might stay capped during the day but if you get something to go could be a structure day at the least.  sfc winds need some work but there might be some local backing near the pseudo warm front. 

Link to comment
Share on other sites
Kmlwx

Kmlwx

Posted
  • Author
Posted

nam pretty ideal for thurs.. maybe a smidge fast as the profile has westerly winds by 0z tho i guess most of our tornado events are mid afternoon around here.  has a nice lee low etc.  hard to trust tho i think that period (wed-thur) is our best shot this year if it holds as it looks on the models. 

 

wed might stay capped during the day but if you get something to go could be a structure day at the least.  sfc winds need some work but there might be some local backing near the pseudo warm front.

I am excited...about as much as we can hope for this far out.

Link to comment
Share on other sites
Ellinwood

Ellinwood

Posted
Posted

I'll take the GFS over NAM.

 

In setups like this NAM does tend to underestimate the CAPE with the clouds+rain hanging around (unless all-day clouds and rain verifies). In this case, GFS should definitely get the lean around DC and south. Perhaps more of a blend the further north you go where the more persistent rain is. A look at the SPC mesoanaylsis shows 2000-2500 SFC CAPE already in eastern VA, so the NAM's certainly off in that area.

Link to comment
Share on other sites
yoda

yoda

Posted
Posted

In setups like this NAM does tend to underestimate the CAPE with the clouds+rain hanging around (unless all-day clouds and rain verifies). In this case, GFS should definitely get the lean around DC and south. Perhaps more of a blend the further north you go where the more persistent rain is. A look at the SPC mesoanaylsis shows 2000-2500 SFC CAPE already in eastern VA, so the NAM's certainly off in that area.

Seems that way... SPC meso has 1500 SBCAPE just east of I-81 corridor with 2000 SBCAPE nosing in to DC area... along with 1000 MLCAPE

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...