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Severe Weather Threat for 5/4/12 - Discussion & Obs


tornadojay

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day2otlk_0600.gif

...NERN STATES...

HEIGHTS WILL FALL AS A SHORTWAVE TROUGH MOVES OVER THE TOP OF UPPER

RIDGE AND SEWD INTO THE NERN U.S.. THE WARMS SECTOR SOUTH OF ANY

ONGOING CONVECTION AND WEST OF A N-S ORIENTED WARM FRONT SHOULD

BECOME MODERATELY UNSTABLE AND STORMS WILL LIKELY INCREASE IN

COVERAGE AND INTENSITY. A BELT OF SLIGHTLY STRONGER 30-35 KT MID

LEVEL FLOW WILL ACCOMPANY THE SEWD MOVING IMPULSE. BOUNDARY LAYER

TEMPERATURE/DEWPOINT SPREADS MAY BECOME SUFFICIENT FOR A THREAT OF

MAINLY ISOLATED DAMAGING WIND.

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Intrigued by tomorrow's setup. You have that low diving SSE down the Hudson Valley and decent shear. If enough instability can be realized..could be an interesting line of storms coming through. Sort of caught my eye.

i can't remember a recent setup like this... usually the front will be hung up over philly/ttn

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i can't remember a recent setup like this... usually the front will be hung up over philly/ttn

Yeah it seems like it will be hung up close to the city. I suppose 500 winds could be a bit stronger and instability may be questionable where best helicity/shear are located, but I thought it looked intriguing. I guess we'll see what the models do today regarding timing of predawn stuff.

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For a few runs the NAM had a convergence zone right near NYC with the surface front/marine layer and was trying to indicate convection along it. I guess it's not completely out of the question with the positioning of the surface low and decent shear. Although the warm front is farther north that boundary could serve as a focal point for some convective development if it does set up as the NAM has advertised. Haven't seen the latest stuff from this AM yet (iPhone post, ewall not loading).

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For a few runs the NAM had a convergence zone right near NYC with the surface front/marine layer and was trying to indicate convection along it. I guess it's not completely out of the question with the positioning of the surface low and decent shear. Although the warm front is farther north that boundary could serve as a focal point for some convective development if it does set up as the NAM has advertised. Haven't seen the latest stuff from this AM yet (iPhone post, ewall not loading).

Yeah it's possible the winds could be more SSE which keeps the threat farther inland. You can see that north-south trough show up on the NAM from the Hudson Valley area right into DC. That's sort of the warm front.

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The thing that I don't like, is that the return flow is going to take forever to advect the marine garbage out of the area. This layer goes all the way to RIC. It's got to move out of ehre and sct out..and it makes me wonder if surface instability will suffer.

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Not to be a debbie downer but haven't we seen setups like this many times before only to get burned? With the way this week has gone I'm just not getting my hopes up.

The thing that I don't like, is that the return flow is going to take forever to advect the marine garbage out of the area. This layer goes all the way to RIC. It's got to move out of ehre and sct out..and it makes me wonder if surface instability will suffer.

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Not to be a debbie downer but haven't we seen setups like this many times before only to get burned? With the way this week has gone I'm just not getting my hopes up.

But you can also get nice MCS type stuff which is elevated...a nice instability burst. In that case, you don't need 80+ temps. That may happen late tonight. If you can clear out tomorrow..the interior could be primed for something nice...just need the sun.

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The thing that I don't like, is that the return flow is going to take forever to advect the marine garbage out of the area. This layer goes all the way to RIC. It's got to move out of ehre and sct out..and it makes me wonder if surface instability will suffer.

I think the severe weather will be relegated ro areas west of NYC for sure. But the models have been trending towards the warm sector broadening over NJ father north towards SE NY/CT.

I think by afternoon we'll see most areas west of the city in the 80s which should support at least adequate instability. The coast will really suffer from the marine layer...so they'll need to have severe convection to the west and maybe some elevated instability if they want to see some action.

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But you can also get nice MCS type stuff which is elevated...a nice instability burst. In that case, you don't need 80+ temps. That may happen late tonight. If you can clear out tomorrow..the interior could be primed for something nice...just need the sun.

rad16.gif nam for later tonight

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the time stamp is correct... the maps i posted are from a regional high res nest

12z NAM has the sub 1010mb relative surface low over Northeast PA/Southeast NY at 18z tomorrow..warm sector through NJ with mid 80s temps.

The NAM would be decent I think for tstms int he aftn. I guess the question I have is how quick does this crap retreat? Models love to rush it.

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The NAM would be decent I think for tstms int he aftn. I guess the question I have is how quick does this crap retreat? Models love to rush it.

the 0z and 6z nam runs kept the warm front west of nyc, so this is a big step in the right direction

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The low travels in such a weird way. Goes due east across nrn NY and then almost due south over the Hudson valley. NAM brings the line right in at 21z and it looks healthy.

It's going along that marine layer/wind shift boundary which runs N to S through NYC...just E of NJ...I think. Pretty weird.

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It's going along that marine layer/wind shift boundary which runs N to S through NYC...just E of NJ...I think. Pretty weird.

Yeah I sort of like the look from the srfc to 500mb. Shear is decent both from velocity and direction. Hopefully it ends up producing.

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Looks like the first decent threat tomorrow. The NAM has NJ approaching nearly 2000 J/kg of SBCAPE with LIs of -4 to -6, temperatures in the mid-80s and dewpoints in the low- to mid-60s. 25-30kts of shear isn't too great but should be sufficient for enough storm organization as they move from in from the NW. The NAM seems to be creating a decently large MCS as significantly negative ω is apparent at 700 hPa. Widespread severe threat doesn't look too promising though with only okay mid-level lapse rates and weak-ish winds aloft.

nam_cref_zoom_36.png

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Can't currently load up BUFKIT so I haven't reviewed the run much, but the 4km reflectivity still looks to bring a nice MCS through N NJ/NYC tomorrow afternoon.

nam_cref_zoom_21.png

2 m temperatures are well into the mid-80s across NJ by late afternoon via the NAM.

nam_t2m_ne_20.png

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Can't currently load up BUFKIT so I haven't reviewed the run much, but the 4km reflectivity still looks to bring a nice MCS through N NJ/NYC tomorrow afternoon.

2 m temperatures are well into the mid-80s across NJ by late afternoon via the NAM.

Very well defined on the e-wall high resolution maps as well.

rad21.gif

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The one intriguing thing to me that stands out is there will be steep lapse rates in place on order of 6.5-7 C/KM. Normally when we see these setups where the warm front gets hung up we deal with very good shear and we all hope we can get enough breaks of sun to get some 1000-1500 J/KG Cape values. Well this time we have very good lapse rates and alright shear. While helicity won't be impressive there will be some helicity in place with the warm front nearby.

I think the setup favors the potential for severe strong to severe storms with large hail as the number 1 threat given the presence of steep lapse rates and helicity likely on order of 100-150 m2s2...should be enough for some storms to rotate increasing hail potential.

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