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Severe weather potential April 11, 2011


IsentropicLift

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Lifted index doesn't agree....anyway the second line is the one we want apparently

The Lifted index is just measure of instability. Alot of times, we've had good LIs, CAPE, and shear, but we get little or nothing to form, because the lifting is weak. The best lift is with the cold front back over Western PA right now. So we have to wait for the cold front to get closer, to see more showers or t-storms. But the instability will diminishing over the area evening hours, and sea-breeze front has already moved into NYC. So I think t-storms will weaken as the east into NJ and become more elevated when the reach NYC overnight.

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The Lifted index is just measure of instability. Alot of times, we've had good LIs, CAPE, and shear, but we get little or nothing to form, because the lifting is weak. The best lift is with the cold front back over Western PA right now. So we have to wait for the cold front to get closer, to see more showers or t-storms. But the instability will diminishing over the area evening hours, and sea-breeze front has already moved into NYC. So I think t-storms will weaken as the east into NJ and become more elevated when the reach NYC overnight.

You can have all the instability in the world but if you don't have a triggering mechanism you are essentially left with one giant c*** tease.

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You can have all the instability in the world but if you don't have a triggering mechanism you are essentially left with one giant c*** tease.

understood, but those storms that were in central PA earlier had already formed and were fairly strong for a short time. Amazing how you could have 99% of the ingrediants needed for severe weather and still come up short. :arrowhead:

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Things looking better again..per latest radar, convection is really firing over eastern PA

mcd0416.gif

MESOSCALE DISCUSSION 0416

NWS STORM PREDICTION CENTER NORMAN OK

0543 PM CDT MON APR 11 2011

AREAS AFFECTED...MD/CNTRL AND ERN PA/CNTRL AND ERN NY

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 112243Z - 112345Z

A FEW THUNDERSTORMS CAPABLE OF DMGG WINDS MAY DEVELOP FROM MD NWD

INTO PORTIONS OF CNTRL/ERN NY. GIVEN EXPECTED TRENDS AT THE

MOMENT...A WW IS NOT ANTICIPATED...BUT THE AREA WILL CONTINUE TO BE

MONITORED.

STRONG DIURNAL HEATING AND LOW LEVEL WARM ADVECTION REGIME HAS LED

TO WELL ABOVE NORMAL TEMPERATURES ACROSS THE NORTHEAST...WHILE DEW

POINTS IN THE LOWER 60S HAVE REACHED MD/ERN PA...AND MID TO UPPER

50S FARTHER N. HOWEVER...APPEARANCE OF GENERALLY STRATUS

CLOUDS...LACK OF TOWERING CU/CONVECTIVE TYPE CLOUD STRUCTURES ON

VISIBLE SATELLITE IMAGERY AND LACK OF LIGHTNING WITH THE EXCEPTION

OF CNTRL NY INDICATES THAT STRONG CONVECTIVE INHIBITION STILL

REMAINS. PER RECENT WV IMAGERY...AN UPPER TROUGH AND IMPLIED UPPER

ASCENT STILL REMAINS WEST OF THE AREA OVER SERN ONTARIO SWD INTO THE

OH VALLEY...AND GIVEN NEUTRAL TO WEAK HEIGHT FALLS THROUGH PEAK

DIURNAL HEATING...MAY HAVE ALSO LIMITED MORE WIDESPREAD CONVECTIVE

DEVELOPMENT. HOWEVER...RECENT RADAR IMAGERY INDICATES THAT A

PREFRONTAL TROUGH EXTENDING THROUGH CNTRL NY SWD INTO ERN PA THEN

SWWD THROUGH WV MAY PROVIDE SUFFICIENT FORCING FOR ASCENT...ALLOWING

A FEW THUNDERSTORMS TO DEVELOP WHERE CINH IS WEAKER. ADDITIONAL

CONVECTION MAY BE POSSIBLE AS THE AFOREMENTIONED UPPER WAVE/HEIGHT

FALLS AND ASSOCIATED SURFACE COLD FRONT QUICKLY APPROACH FROM THE

WEST...THOUGH RADIATIONAL COOLING WILL LIKELY LIMIT A MORE

WIDESPREAD THREAT OF SEVERE THUNDERSTORMS. HOWEVER...SHOULD STORMS

DEVELOP...STRONG WIND FIELDS WOULD SUPPORT DMGG WINDS.

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You can have all the instability in the world but if you don't have a triggering mechanism you are essentially left with one giant c*** tease.

I would have to say we have a very favorable trigger mechanism with the pre-frontal shortwave trough over Central PA and plenty of forcing for ascent (see the NAM for the shortwave) With 60 kts of 0-6km bulk shear over Central PA these updrafts should have no trouble sustaining themselves. The question remains how they will react to the elevated instability and more stable boundary layer further east.

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I would have to say we have a very favorable trigger mechanism with the pre-frontal shortwave trough over Central PA and plenty of forcing for ascent (see the NAM for the shortwave) With 60 kts of 0-6km bulk shear over Central PA these updrafts should have no trouble sustaining themselves. The question remains how they will react to the elevated instability and more stable boundary layer further east.

these were not present earlier which is why the storms died

I'm on the general thunderstorm train tonight, but not the severe train.

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The first batch fell apart up near Sussex county. We'll see if the more potent line in E. PA can hold together a while though I'd be surprised if we saw more than a downpour and some thunder and lightning.

2000 j/kg of MUCAPE over Western New Jersey will certainly do the trick..the tongue of elevated instability suggests these could get to Newark before losing their punch.

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All in all, this is a non-event, time to unpin this thread.

this would have been a great severe weather day in the summer with dynamics to work with. But today, it was for sure a none event for NYC metro. That line went thru a shredder. Atleast we all stay warm :thumbsup:

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this would have been a great severe weather day in the summer with dynamics to work with. But today, it was for sure a none event for NYC metro. That line went thru a shredder. Atleast we all stay warm :thumbsup:

I like that anology, went through a shredder

Yup, marine stability will do that to you.

Give me this setup in June/July and I will honk non stop.

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Didn't have anything to do w/ a marine layer, but everything to do with the front simply losing its dynamics and falling apart. The line of storms was never impressive, even back in CPA. The front is rapidly fading, but low pressure will develop along its boundary to give us the crappy next 2 days.

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Didn't have anything to do w/ a marine layer, but everything to do with the front simply losing its dynamics and falling apart. The line of storms was never impressive, even back in CPA. The front is rapidly fading, but low pressure will develop along its boundary to give us the crappy next 2 days.

I guess we will have to wait until May for our area to get into the fun. Believe or not I would of took the elevated convention any day over nothing because they produce a great amount of thunder and lightning. Thundersleet event for example that occurred few weeks ago was incredible. In May the waters warm a bit also but sometimes the marine air doesn't play the factor either and you need a good setup for everything to go right for convention. June would even be better where even LI does most part over come the marine alot of the times but the best storms come to LI when they come from the NW and they usually survive that direction some reason and that is when LI get the best chance for severe weather. On the other NYC has better luck with any direction of storms in the late spring and summer. You need good instability and not too strong of shear to keep the storms to maintain themselves. April is usually the month for the area to just get their general thunderstorm activity but chances are so low for severe weather because the waters are so cold and that keeps the marine layer so strong especially for LI and coastal CT.

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Okay. Now you can color me excited

this model started acting screwy at the end of the winter, not sure whats wrong with it, but last year you would have never seen it go so gung ho on a line of storms a few hours before they were to hit the area and the end result was nada.

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Didn't have anything to do w/ a marine layer, but everything to do with the front simply losing its dynamics and falling apart. The line of storms was never impressive, even back in CPA. The front is rapidly fading, but low pressure will develop along its boundary to give us the crappy next 2 days.

Not so sure about that. There was a line of storms over the hudson valley last night that totally died moving east as they encountered the more stable marine induced airmass. Those storms should have been able to hang on but for that.

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Not so sure about that. There was a line of storms over the hudson valley last night that totally died moving east as they encountered the more stable marine induced airmass. Those storms should have been able to hang on but for that.

It was really the combination of weakening instability and lack of dynamic lifting, why we didn’t get more t-storms last night. The instability began to rapidly diminish after sunset. And the ULL developing to the south was robbing us off better dynamics.

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It was probably a combination of things. Around 6-7pm, Surface based CAPE over most of NJ and eastern PA was in the 1000-2000 J/KG with pockets of even higher CAPE aloft. By the time the last line moved through, it had weakened to about 500+ J/KG. I'm still puzzled as to why the first line weakened so much. The instability was there, the shear was excellent, the mid and low level lapse rates were good and we did have a good forcing mechanism to initiate convection. As earthlight said last night, the updrafts should have been able to sustain themselves alot longer than they did. One of those mysteries where we won't ever truly know what happened. Perhaps a met or two could chime in with a more scientific explanation.

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It was probably a combination of things. Around 6-7pm, Surface based CAPE over most of NJ and eastern PA was in the 1000-2000 J/KG with pockets of even higher CAPE aloft. By the time the last line moved through, it had weakened to about 500+ J/KG. I'm still puzzled as to why the first line weakened so much. The instability was there, the shear was excellent, the mid and low level lapse rates were good and we did have a good forcing mechanism to initiate convection. As earthlight said last night, the updrafts should have been able to sustain themselves alot longer than they did. One of those mysteries where we won't ever truly know what happened. Perhaps a met or two could chime in with a more scientific explanation.

I still dont see a good forcing mechanism to sustain that initial line, it clearly outran the support.

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