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2013 Mid-Atlantic Severe General Discussion

Kmlwx

By Kmlwx,
in Mid Atlantic

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yoda

yoda

Posted
Posted

I actually don't know what to call the thing models are depicting.  It's a legit mini H5 troff that moves quickly across the country. It will probably have a bow echo associated with it. It needs to be quicker and less amplified to look like a derecho.

 

00z NAM def has that... but its moving east late in the period (66 in NW IA to 84 NE OH) on the h5 charts and it strengthens as it moves eastward... its trajectory would take it north of us into PA if it were correct... unless it suddenly decides to pull a SE turn

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Amped

Amped

Posted
Posted

00z NAM def has that... but its moving east late in the period (66 in NW IA to 84 NE OH) on the h5 charts and it strengthens as it moves eastward... its trajectory would take it north of us into PA if it were correct... unless it suddenly decides to pull a SE turn

Rest of the real models still track the low over us. GFS has a 996 low that tracks off the Del Marva and skims cape cod. Interesting H7 map, at 114 but it's probably a feedback error.

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Ellinwood

Ellinwood

Posted
Posted

SPC tornado probs map from this morning look a little bullish, but the discussion makes more sense compared to what I was thinking for today.

day1probotlk_20130610_1200_torn_prt.gif

...CAROLINAS INTO VA...MD...PA...DE...
SUBSTANTIAL CLOUDS AND AREAS OF PRECIPITATION WILL ADD UNCERTAINTY
TO THE EVOLUTION OF STORMS TODAY. HOWEVER...A GENERAL INCREASE IN
CONVECTION IS EXPECTED AS THE UPPER TROUGH NEARS AND POCKETS OF
HEATING AND SWLY FLOW HELP TO DESTABILIZE THE WARM SECTOR. THERE
WILL BE LITTLE IF ANY CAPPING...THUS SUBTLE FORCING MECHANISMS SUCH
AS BOUNDARY LAYER CONFLUENCE WITHIN THE DEEPENING SURFACE TROUGH
WILL BE ENOUGH TO FORCE STORMS.

HODOGRAPHS WILL BECOME LONGER DURING THE DAY...WITH SUPERCELLS
LIKELY. LOW LEVEL VEERING WILL NOT BE STRONG...BUT SUFFICIENT FOR A
TORNADO OR TWO GIVEN MOIST BOUNDARY LAYER CONDITIONS. THE MOST
CONCENTRATED AREA FOR SUPERCELLS SHOULD BE FROM CNTRL/ERN VA INTO MD
AND SRN PA.

ALTHOUGH THE TORNADO THREAT IS LESS FARTHER N INTO PA...THIS AREA
MAY RETAIN THE LARGEST LOW LEVEL HODOGRAPHS DUE TO PASSAGE OF EARLY
PRECIPITATION AND WARM FRONT. IN ADDITION TO SUPERCELLS...WHICH MAY
FORM EITHER ALONG THE COLD FRONT OR ACROSS THE WARM
SECTOR...MODERATE DEEP LAYER MEAN WINDS WILL FAVOR A FEW BOWS OR
LINES WITH DAMAGING WINDS.

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H2O

H2O

Posted
Posted

the derecho talk is pretty funny

 

   
*** ALERT ** 1ST POSSIBLE DERECHO EVENT OF THE SEASON FOR OHIO VALLEY and MIDDLE ATLANTIC Wed afternoon ...evening ...into early Thursday morning

Here is the 18z WRF /NAM ... at 72 hrs ( top 3 maps) and six hours later at 84 hrs . The LEFT maps are UPPER AIR ( 500mb) .. and shows a Powerful piece of energy in the Jet stream over Chicago ( CIRCLE IN YELLOW) ... 6 hours later that feature is over IND/ OH., The huge cluster of storms over southern WI and raced ESE .. classic DERECHO track-- into southeast MI and Northeast OH.

IF .... IF .. this is correct the DERECHO would hit western and / or central PA western / central MD and DEL... It Might skim Northern VA early Thursday morning

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yoda

yoda

Posted
Posted

So long as we have cloud cover, I don't see anything happening today.

 

Thats what I thought.... but apparently LWX sees different

 

GIVEN CLOUDS/SHOWERS TO START THE DAY...AMOUNT OF INSTABILITY IS

SOMEWHAT UNCERTAIN. MODELS FAVOR CLOSE TO 500 J/KG...BUT SOUTH OF

THE WARM FRONT IF THERE ANY BREAKS THIS COULD EASILY BOOST VALUES

AOA 1000 J/KG. EVEN IF INSTABILITY REMAINS

WEAK/MARGINAL...AFOREMENTIONED SOUTHERLY LOW LEVEL 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.

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Kmlwx

Kmlwx

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Posted

Scattered clearing starting in WV and SW VA.

We know how these things work - the clearing will just never make it to the bulk of us. There will be like one good storm later on in an isolated spot and the rest of us will fail and just get flooding.

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NJwinter23

NJwinter23

Posted
Posted

Sheesh that didn't take long for people to start running with the D-word. In all seriousness, I like the *potential* for some sort of long tracking MCS across the Midwest, possibly into the mid-atl late Wed. That is an impressive looking temp boundary with dews probably around 70 on the southern reaches there. I do not see an EML which was mentioned in a prev post, and I dont see 105/75 in DC (hottest ever June day) so yeah..but models are picking up a meaningful short wave that would spark and help sustain a system. If I'm not mistaken, last year's June 29th event had a very subtle trigger, and no shortwave providing/sustaining the lift..It was all driven by a cold pool from there, and that's all it needed. 

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Ian

Ian

Posted
Posted

It's a pretty good mid lvl trough passage historically. Most of our svr events are kind of meh. Hard to be too down on it with the right expectations. If it wasn't going to try to rain all day might be more fun..

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snowfan

snowfan

Posted
Posted

woah....take it easy. I was nearly run off the board last year for suggesting our weather was boring. Remain calm and hope for a derecho, some F 0's and torrential downpours this week.

I've given up on seeing exciting weather in the MA...guess I'll have to move to the Midwest.

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HM

HM

Posted
Posted

It's a pretty good mid lvl trough passage historically. Most of our svr events are kind of meh. Hard to be too down on it with the right expectations. If it wasn't going to try to rain all day might be more fun..

 

 

There are breaks to the south, it's definitely not write-off time at 10am.

 

Yep. The morning thoughts on 4/19 were also pretty negative and wrong and then LWX ended up confirming a couple of TORs in the area:

http://www.spc.noaa.gov/exper/archive/event.php?date=20130419

 

Overall, it is setups like these that usually bring the northern Mid Atlantic their tornado threat (probabilistically-speaking of course): deep moisture, low LCL, decent directional/speed shear with enough CAPE (storm-relatively balanced of course).  

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