Browse Month

August 2011

Mid-Atlantic Discussion – Aug 9, 2011

Aha! Another chance for storms! But what’s THIS?!? Latest models say best dynamics will be to the north in eastern PA and NJ?

If enough instability can get going up that way, that’s where I’ll be chasing tomorrow. Pretty nice wind field coupled with modest CAPE, with one of the stronger vort. maxes we’ve seen in the region lately and left-exit region goodness from the 300mb jet… things are shaping up nicely per the latest models.

For the Mid-Atlantic states south of the Mason-Dixon, there will still be a severe threat as this shortwave trough moves through the region. The secondary low and its associated cold front will pass through the region tomorrow, providing the risk for severe winds and possibly severe hail. There is a very, VERY minor chance of tornadoes along and just ahead of the front, as some low-level veering is possible but will likely be dominated by the very deep column of unidirectional shear.

Of course, all of this stuff is changing on a run-by-run basis and we could be looking at something completely different tomorrow… it will all depend on what the next 18 hours does in terms of rain, clouds and timing and placement of the developing secondary low.

Tuesday’s severe was fail… more fail on the way?

While it looks like our wind shear has been improving in recent days (to trigger severe weather), the lapse rates and lower surface temperatures have killed that potential as CAPE struggles to achieve even decent amounts of 500-1000 J/kg. Couple that with cloud cover and you’ve got a recipe for boring showers and moderate rain. That was what happened a few days ago, and this should be the story through Monday as the dynamics and instability fail to come together in any sort of significant way.

This upcoming Tuesday could give us a decent chance of severe weather, but we could end up running into more of the same issues.

Mid-Atlantic Discussion – Aug 3, 2011

So… here we are a month after the last Mid-Atlantic write-up (the event failed, BTW) with a new threat and different variables as we look at tomorrow’s severe weather.

Gonna just list the pros and cons and go from there:

PROS:
– Good low-level speed and directional shear.
– Excellent low-level lapse rates.
– Upper-level support via 500mb vort. max and some influence from the jet.
– Winds are veering throughout the column.

CONS:
– Possible cloud cover from storms to the northwest could inhibit heating.
– Lackluster mid-level lapse rates (could change for the better if dynamics are stronger).
– Upper-level jet is perhaps too far away to have a significant impact and we are not in the ideal (upper-level divergence) part of the jet.
– Main line of storms could come in just a bit too early for optimal destablization.
– High LCLs.

With everything put together, it looks like a pretty mixed bag between meh and awesome. I’m going to put tomorrow’s chasing chances at 50%… some nowcasting is definitely for tomorrow’s storms, so there’s no reason to decide on anything now. No idea where I’m going to go yet, either (should I end up going). Primary threat is wind… could see a tornado or two out of it if the instability is good enough.

SPC’s thoughts:

…MID ATLANTIC REGION…
A RATHER STRONG SHORTWAVE TROUGH NOW OVER THE DAKOTAS WILL TRACK
ACROSS THE GREAT LAKES AND INTO THE MID ATLANTIC STATES ON
WEDNESDAY. SEVERAL CLUSTERS OF THUNDERSTORMS ARE ONGOING TODAY WITH
THIS FEATURE…AND WILL LIKELY PERSIST INTO TOMORROW. MODEL
GUIDANCE SUGGESTS THESE CONVECTIVE CLUSTERS WILL BE OVER PARTS OF
LOWER MI/NY/PA/OH AT 12Z. THERE IS CONSIDERABLE UNCERTAINTY
REGARDING THE EXTENT OF CLOUD COVER AHEAD OF THE STORMS…WHICH WILL
IMPACT THE DEGREE OF AFTERNOON DESTABILIZATION OVER THE MID ATLANTIC
REGION. HOWEVER…RATHER STRONG LOW AND MID LEVEL WIND FIELDS
ASSOCIATED WITH THE UPPER TROUGH POSE SUFFICIENT CONCERN TO INCLUDE
THIS REGION IN A SLIGHT RISK FOR SEVERE STORMS. THE MOST LIKELY
THREAT WOULD BE AN ORGANIZED MCS TRACKING THROUGH THE AREA DURING
THE AFTERNOON PRODUCING LOCALLY DAMAGING WIND GUSTS.

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