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Spring severe weather chatter


Ian

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Perhaps meh severe Friday... then LWX AFD hints at maybe a better threat towards the end of the period

 

Hopefully it doesn't fizzle (probably will) as it gets closer. Not much excitement to talk about around these parts lately. Pretty boring. 

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Definitely liking the Sunday setup, at least as currently progged:     strong cold front arrives during late afternoon with significant height falls and moderate instability.      Directional shear is negligible, but the speed shear is strong:  50 kt mid-level jet and 75 kt upper jet, with a 90 kt upper jet core over PA, putting us in the favorable right rear quadrant.     Nice setup for a squall line with a fair amount of wind damage.

 

Of course, the details will be resolved, but there is overall model agreement with the arrival of the strong upper trough, so the SPC day 5 outlook makes sense.     The timing could get messed up and ruin the setup, but on the other end of the spectrum,  if the sfc low ends up deepening more rapidly to our northwest, that in theory could back the low-level flow and introduce some supercell potential.

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Definitely liking the Sunday setup, at least as currently progged:     strong cold front arrives during late afternoon with significant height falls and moderate instability.      Directional shear is negligible, but the speed shear is strong:  50 kt mid-level jet and 75 kt upper jet, with a 90 kt upper jet core over PA, putting us in the favorable right rear quadrant.     Nice setup for a squall line with a fair amount of wind damage.

 

Of course, the details will be resolved, but there is overall model agreement with the arrival of the strong upper trough, so the SPC day 5 outlook makes sense.     The timing could get messed up and ruin the setup, but on the other end of the spectrum,  if the sfc low ends up deepening more rapidly to our northwest, that in theory could back the low-level flow and introduce some supercell potential.

Drool worthy. Don't get us all excited. 

If nothing else we can get another test of the system of who gets excited vs how big the event is. 

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12z CIPS guidance - pretty nice signature for our area. 

June 1, 2012 has shown up in the analogs for a few runs now. This run it is ranked at #6. That is by far the most robust analog that has been spit out for our area with a few others with iso severe. Have to imagine a 6/1/12 would be about the max potential. Would hedge quite a bit lower at this point. 

4x8Dl0S.png

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As has been discussed the past several days, severe weather is

possible over parts of the Mid-Atlantic Sunday as wind field

increases coincident with adequate instability. Though, run-to-run

consistency has made it difficult to delineate the highest threat

area. Current indications are that areas along and east of I95 will

have the greatest opportunity to recover ahead of cold frontal

passage. Fully expect this forecast to change as details become

clearer.

 

From the afternoon discussion from LWX. 

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:o

 

post-397-0-08258800-1464858573_thumb.gif

 

 


ZCZC SPCSWOD48 ALL   ACUS48 KWNS 020901   SPC AC 020901   DAY 4-8 CONVECTIVE OUTLOOK     NWS STORM PREDICTION CENTER NORMAN OK   0401 AM CDT THU JUN 02 2016   VALID 051200Z - 101200Z   ...DISCUSSION...   GFS AND ECMWF RUNS FROM 02/00Z CONTINUE TO EXHIBIT FAIRLY GOOD   MODEL-TO-MODEL AND RUN-TO-RUN CONSISTENCY...SPECIFICALLY WITH THEIR   DEPICTION OF THE EVOLUTION OF A LARGE ERN U.S. STORM SYSTEM.  BOTH   MODELS ADVANCE A LARGE MID-LEVEL TROUGH EWD ACROSS THE ERN U.S. DAY   4 /SUN. 6-5/...WITH AN ASSOCIATED SURFACE CYCLONE INVOF SRN   ONTARIO/LK HURON VICINITY DURING THE AFTERNOON.  AS A TRAILING COLD   FRONT CROSSES THE APPALACHIANS AND SHIFTS INTO THE E COAST   STATES...WIDESPREAD CONVECTION -- LIKELY ALREADY UNDERWAY W OF THE   MOUNTAINS ALONG THE FRONT AND FROM THE MID-ATLANTIC REGION NWD IN A   WARM ADVECTION ZONE AT THE START OF THE PERIOD -- SHOULD INCREASE   STEADILY INTO THE AFTERNOON HOURS.   PRESUMING AMPLE DESTABILIZATION CAN OCCUR AHEAD OF THE FRONT /WHICH   MAY BE DIFFICULT FROM ROUGHLY ERN PA AND NJ NWD DUE TO MORE   PERSISTENT PRECIPITATION AND ASSOCIATED CLOUD COVER/...STORMS SHOULD   ORGANIZE LINEARLY AND INTENSIFY WITH TIME -- AIDED BY STRENGTHENING   SWLY FLOW THROUGH A DEEP TROPOSPHERIC LAYER AHEAD OF THE UPPER   TROUGH.  ALONG WITH SOME RISK FOR HAIL...IT APPEARS THAT A FAIRLY   WIDESPREAD DAMAGING WIND EVENT MAY EVOLVE ACROSS PORTIONS OF THE   MID-ATLANTIC REGION AND SWD INTO NC -- PRESUMING AMPLE   HEATING/DESTABILIZATION CAN OCCUR.  RISK APPEARS GREAT ENOUGH ATTM   TO INTRODUCE 30% RISK AREA ACROSS THIS REGION...WITHIN THE BROADER   PRE-FRONTAL SLIGHT RISK ALONG AND E OF THE APPALACHIANS BEING   MAINTAINED FROM THE PRIOR OUTLOOK.
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Sunday could have some morning showers/storms and then clear out and the severe storms would start mid to late afternoon and into the evening. GFS and NAM have 2000-3000+ CAPE and sufficient shear, Sharpy has us in a classic supercell profile region wide through the afternoon and evening.

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Many of our high ends days seem to have three common ingredients:

 

1.)  Quick movement into the warm sector, but having the surface warm front nearby.

2.)  Good directional shear.

3.)  Robust mid level lapse rates.  

 

 

These will be the key factors to look for on Sunday.  Obviously #3 is dependent on #1, but the June 2012 event was compensated by the proximity of a strong warm front so we'll see.

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Afternoon disco from LWX:

 

A strong mid/upper-level trough will pivot towards the area
during the second half of the weekend. A surge of higher dew point
air in the low-levels will move across the region Sunday afternoon
ahead of this trough. The overall setup is very similar from model
to model and from run to run, but timing differences remain. The
potential exists for a substantial severe weather event Sunday
afternoon and evening as long as sufficient destabilization can
occur.

In favor of severe weather is a strengthening 700-500 mb wind field
in excess of 50 knots by evening as well as cooler mid-level
temperatures and an influx of moisture in the low levels. Working
against severe weather would be a stronger low level jet and
potential clouds or unfavorable frontal timing (which as mentioned
above is still uncertain). If the front comes through during the
evening hours that will allow for maximum heating and
destabilization and thus the greatest risk of severe weather. The
warm and humid airmass would tend to suggest damaging winds and
heavy rain would be the primary threats, though large hail would be
possible with the strongest cells. SPC already has much of the area
in a 30% probability for severe weather Sunday despite possible
negative factors, so no matter how you slice it Sunday looks active.
Later trends will have to be watched closely to see if an even
higher threat develops.
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That's the hope. SPC is bullish on this one. I'm still waiting for Ian to get on board. 

We may get some severe, there is a 0% chance of the sun coming out for more than 5 minutes in a row like most events in this area.

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    yes, but because it breaks out a fair amount of precip out ahead of the front throughout the afternoon which eats away at the cape.   By early afternoon, the model shows cape in the 1500-2000 range, and one would expect that to go a little higher *if* we continue to heat.  Having widespread pre-frontal convection is certainly one of the fail mechanisms for this event, but I think that there is still a good chance that we'll stay dry through the afternoon and fully destabilize.

 

 

Looks like the NAM may have backed off on the instability a bit to my untrained eye?

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Most of area in day 3 ENH.

...MID ATLANTIC REGION...

AMPLE MOISTURE AND DAYTIME HEATING WILL COUNTERACT RELATIVELY WARM

TEMPERATURES ALOFT AND YIELD AROUND ON THE ORDER OF 1500 J/KG MUCAPE

ACROSS THE WARM SECTOR BY MID AFTERNOON. WIND SHEAR PROFILES ARE

EXPECTED TO STRENGTHEN RAPIDLY DURING THE AFTERNOON AS THE SHORTWAVE

TROUGH APPROACHES. MEAN FLOW OF 40-50 KT IN THE 850-500 LAYER WITH

INCREASING SPEED SHEAR IN THE UPPER LEVELS WILL RESULT IN LONG

HODOGRAPHS FAVORABLE FOR LONG-LIVED SEVERE STORMS INCLUDING A FEW

SUPERCELLS. GRADUALLY VEERING 850 MB FLOW AND THE ABSENCE OF A

SURGING COLD FRONT SUGGEST SUPERCELLS AS THE DOMINANT STORM MODE

DURING THE DAY...WITH PERHAPS MERGING OF CELLS LATER IN THE EVENING

AS STORMS EXIT THE COAST. HAIL...DAMAGING WINDS AND A FEW TORNADOES

WILL BE POSSIBLE.

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