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Spring/ Summer 2014 Convection Discussion


weatherwiz

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One thing I noticed from both the GFS and ECMWF is that the highest bulk shear does not encroach very aggressively into the high theta-e side of the forcing boundary. There is still good overlap of the 40 kt shear and 1000+ j/kg instability areas, but the 50+ kt shear is still a bit west of the boundary. Also the surface winds are not backed very much (or at all) so the hodographs look pretty straight. With all of that said it still looks like a decent setup for severe weather.

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Going to be quite difficult to really pin down the exact threat area but right now I like central/eastern NY into VT, SW NH, western MA, and western CT.  

 

As far as the setup goes, as stated, this is highly anomalous with the most eye opening aspect of the setup being with the dynamics.  While we could see dynamics like this associated with a coastal system to have dynamics like this with a trough/shortwave and an attendant cold front this time of year is quite rare.  We are looking at a solid presence of 45-55 knots possible at 500mb...the GFS/Euro have also hinted that we could see a jet streak exceeding 75-85 knots round the base of the trough...that's quite impressive for mid-July.  If that's not impressive enough the ULJ is even more impressive with 200mb winds of 80-100 knots placing at least western sections of New England in the RFQ and there is a 120+ knot ULJ streak.  

 

Meanwhile at the sfc, all models indicate that the warm front will push through sometime Sunday/Sunday night and once that blows through much warmer and much more humid air will work into the region.  Quincy posted the Euro showing dews near the mid-70's...typically you would think that's overdone, however, given the setup, strength of southerly flow and theta-e advection...dews in the 73-76F range really may not be completely overdone.  This combination of hot/moist air will lead to the potential for an extremely unstable airmass.  While it doesn't appear we will see an EML advect in which would escalate the potential and instability...GFS bufkit soundings are respectable with 700-500mb lapse rates around 6-6.5 C/KM.  

 

Given the presence of some pretty crazy wind shear and potential for some very high instability, this certainly needs to be watched very closely.  All we have to do here is look back at the past few days and what we saw occur in some places.  When you're dealing with 35-40+ knots of bulk shear you don't need much instability and in the case of early next week we could be dealing with at least 45-55 knots of bulk shear.  When you start getting values that high though you do need stronger buoyancy though or otherwise the updrafts will struggle to really grow tall enough...this is where jet quadrants and instability become important (or very steep lapse rates).  

 

At this time though it's difficult to really get into specifics as to what to expect in terms of severe type...however, I think all severe hazards are on the table (damaging winds, large hail, and isolated tornado threat) but the details needed to get into these specifics won't be known for a few more days.  

 

What I will say though is we could be dealing with the potential for quite the damaging wind event from NY/PA and that could extend into portions of New England but it just all depends on timing.  

 

As Scott mentioned, flash flooding could be a pretty high threat as well...while this setup is favorable for strong to severe t'storms, it is also favorable for training thunderstorms and the patter will support numerous convection at times...add in very high PWATS and you have a recipe for flash flooding potential...and again where the highest threat for flash flooding exists will all depend on what areas are hardest hit Monday/Tuesday timeframe.  

 

I also think we have to watch late Sunday PM for the possibility of some strong to severe t'storms as well with the warm front...GFS a bit more aggressive than the NAM but I don't think it can be ruled out.  

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We've lost our Tuesday severe threat from SPC........storm canceled.  O well

This to me looks like a classic east coast flood threat with numerous waves of convective heavy rains riding north along the coast as opposed to severe storms. The enviornment should be supportive of widespread development with tons of convective debree and cloud cover somewhat limiting SBCAPE instead of one that would support discrete development and supercells.

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This to me looks like a classic east coast flood threat with numerous waves of convective heavy rains riding north along the coast as opposed to severe storms. The enviornment should be supportive of widespread development with tons of convective debree and cloud cover somewhat limiting SBCAPE instead of one that would support discrete development and supercells.

We want more eml/capping to keep storms discrete. The sultry pwats and storm track reminds me of last year's atmospheric river gushers. Hoping something more interesting evolves, but odds are you'll need to be west to get the goods IMHO.

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No mention of EML or cap.. unidirectional winds.. extremely moist atmosphere.. 

 

It sounds like some wind gusts and a lot of rain to me.

Training storms with perhaps enbedded super cells and line segments where the stronger shear axis sets up. Think the sweet spot right now is PA/NY for more organized severe. Primary storm mode from NYC to Boston should be multicellular which could eveolve into more organized convective complexes. Storm motion should be relatively parallel to the mean flow so flash flooding looks to be possible.

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Training storms with perhaps enbedded super cells and line segments where the stronger shear axis sets up. Think the sweet spot right now is PA/NY for more organized severe. Primary storm mode from NYC to Boston should be multicellular which could eveolve into more organized convective complexes. Storm motion should be relatively parallel to the mean flow so flash flooding looks to be possible.

We need to keep an eye on areas that have seen a lot of rain recently also. 

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I wouldn't be shocked to see the SPC revive the threat for tuesday in their 4-8 outlook tomorrow, still seems to be fairly consistent on the models.  GFS has brought back the precip max that runs from SNY to ME, which bodes well for a potential for an organized MCS of some sort.  Models are horrific at handling those this far out though.

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I wouldn't be shocked to see the SPC revive the threat for tuesday in their 4-8 outlook tomorrow, still seems to be fairly consistent on the models. GFS has brought back the precip max that runs from SNY to ME, which bodes well for a potential for an organized MCS of some sort. Models are horrific at handling those this far out though.

Their discussion, at least this morning, said it was a function of the ensemble models losing the consensus needed for 30%, but that there was still a good chance of severe during the period in the NE. I wouldn't be surprised if it ended up a slight risk though, or completely a nonevent east of the river as usual.
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Something tells me the gfs is suffering from its usual mid-range wobbling for Tuesday. Euro and unmet, as noted by the SPC, are still favorable for severe here. Interesting to see the SPC being put off by one wobbly model when the others have been relatively consistent.

The SPC referenced the Euro ensembles, which are faster. In fact, several of its members already have the front through most of SNE by 00z Wednesday. Not to mention the SREF and NAM, although in weenie range, also look rather underwhelming for Tuesday as well.
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Anytime you're dealing with the flow aloft parallel to the upper flow and have ridging off to our east it's always best to take the slower timing...like 99.9% of the time.  

 

However, I think sometimes we get too caught up with fropa timing...most of the time convection develops along the pre-frontal trough as opposed to the cold front so it's probably more important to gauge where the pre-frontal will be positioned and the speed of that.

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Anytime you're dealing with the flow aloft parallel to the upper flow and have ridging off to our east it's always best to take the slower timing...like 99.9% of the time.

However, I think sometimes we get too caught up with fropa timing...most of the time convection develops along the pre-frontal trough as opposed to the cold front so it's probably more important to gauge where the pre-frontal will be positioned and the speed of that.

I was wondering that...seems most of the time our good severe is well ahead of the cold fronts. The actual fronts themselves are often just rain showers and a wind shift. The type of stuff where you get a severe storm, but then it's still humid and muggy for a few hours before the actual boundary gets to you.

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I wont its for work unfortunately i work in the moving industry going to dc north carolina then west virginia its a 6 day trip. Going to start looking in the mid atlantic forum for a week lol

Heck - you might even get to see something down here Tuesday if the GFS keeps moving towards the Euro. Hope you enjoy your time in DC!

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I was wondering that...seems most of the time our good severe is well ahead of the cold fronts. The actual fronts themselves are often just rain showers and a wind shift. The type of stuff where you get a severe storm, but then it's still humid and muggy for a few hours before the actual boundary gets to you.

 

Yeah most of the convection we get is produced by pre-frontal troughs as opposed to cold fronts themselves.  When we have those rare setups of extreme instability then we can get multiple rounds of severe...pre-fronts and cold fronts...doesn't happen too often though

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I wont its for work unfortunately i work in the moving industry going to dc north carolina then west virginia its a 6 day trip. Going to start looking in the mid atlantic forum for a week lol

 

Ah, that sucks :P - Hopefully you get to see some good wx while you're here then. 

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