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Trough returns next week


Ginx snewx

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I just think we're gonna be screwed with mid level crap tomorrow. If it's cloudy and 73-77 with dews in the 70-75 degree range there'll be storms..but I doubt we see much severe other than a wet weenie microburst

Thats kind of what happened on 6/6/10...we had amazing shear but garbage mid-level lapse rates and tons of cloud debris made it a huge bust.

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Thats kind of what happened on 6/6/10...we had amazing shear but garbage mid-level lapse rates and tons of cloud debris made it a huge bust.

The thing is though 6/6/10 wasn't really a bust...on the tornado side of it was it? I suppose so but it's not like there wasn't severe wx, there was...and a decent amount of it.

If there was no severe wx at all then you could call it a bust but just b/c there were tornado watches and no tornadoes doesn't necessarily make it a bust...just means that along with the potential for severe wx (winds/hail) storms could produce tornadoes as well.

Activity that day also became more linear rather quickly as opposed to discrete which looking back I think played a MAJOR role in the lack of tornado reports.

Take this past Tuesday for example, the discrete cells that got going were kind of impressive...perhaps if we had more in the way of LL shear something would have dropped. I don't recall the LL shear from 6/6/10 but I don't remember it being all too impressive...LLJ was like 15-20 knots. Tomorrow is a bit more impressive...20-30 knots.

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Good writeup Wiz... I'm personally expecting some decent rains and maybe a tiny rumble of thunder...

Thanks...I just did a more in depth one on facebook

The potential exists for a rather potent severe weather outbreak across portions of NY exteneding eastward into much of central and southern New England with damage winds, large hail, and even a few tornadoes possible. The extent and sevrity of the threat will be HIGHLY dependent on the amount of sunshine we are able to develop tomorrow.

A cold front and upper level trough will be pushing eastward from New York during the day. Rotating around the trough through the region will be a very potent piece of s/w energy. As this feature moves eastward towards our region the winds in the mid levels of the atmosphere will rapidly increase to the order of 35-50 knots. This will yield to strong bulk shear and vertical shear values with bulk shear values in the 25-35 knot range with vertical shear values in the 40-50 knot range. This will be enough for the potential of organized thunderstorms as well as supercells. Winds will be coming from the west/northwest here.

A surface low will also develop across New York state along the cold front and run northeastward along the front. As this feature develops and slightly deepens the winds in the lower-level of the atmosphere will increase as well, in the order of 20-30 knots. Winds here will be more from the southwest. This will also help to increase moisutre and dewpoints.

Given how winds in the lower levels of the atmosphere will be more from the southwest with winds in the mid levels turning to the west/northwest this will create a good deal of directional shear. This will be noted by very high helicity values. 0-3km helicity values have the potential to range from 250-400 m2s2 with 0-1km helicity values potentially ranging from the 200-250 m2s2 range. Not only are these values high enough to warrent the potential for supercells but they are certainly high enough for possible tornadoes as well, especially if there is enough instability present.

One of the biggest issues regarding tomorrow is how much sun will we see across the region? Unfortunately we really won't know this until the AM but an MCS is expected to work across portions of NY and this MCS may taint us with a good deal of cloud debris. EVen if this does occur it doesn't mean the threat is totally dead. If clouds can break up and sun can break out by late morning that still gives us plenty of time for the atmosphere to recover and really start heating and destabilizing. Given how the low level airmass will be very warm it will not take much for the surface to heat rather quickly...such an example occurred this past Tuesday, the 26th of July.

If clouds tomorrow aren't an issue or aren't much of an issue temps across the region (in the areas that receive the most sun) would rapidly warm into the mid 80's...perhaps even upper 80's. This coupled with dewpoints rising into the upper 60's to near 70F would create cape values in the 1000-2000 J/KG range. Given the shear values mentioned aloft that would be more than enough to produce some very nasty severe weather.

If clouds tomorrow are an issue then we only stay in the 70's all day long and this will rapidly reduce cape values, likely keeping them below 1000 J/KG. In this scenario it doesn't mean there won't be any severe weather, it just means severe weather would be much more isolated and torrential rains/flash flooding would likely become a much greater threat. The tornadic threat would also be gratly reduced.

Regarding the tornado threat one other factor that could come into play here is the storm mode. Will storms be more discrete or will they evolve more into line segments? If storms stay more discrete and we have the scenario of greater heating/instability the tornado threat would be highly increased across the region.

If storms evolve into line segments or cluster the tornado threat would be migited and damaging winds would quickly become the greatest threat.

The final thing to watch for is timing of the cold front and the s/w energy rotating through. If the timing can occur mid to late afternoon this would be perfect timing for severe as it would give us the best chance for the atmosphere to recover and have sufficent heating/destabilization. If timing is earlier than that then we run the risk of the atmosphere not having enough time to recover.

All these questions will be ansered in the AM and throughout the AM tomorrow as the satellite trends can be watched and there will be a much better idea on how much sun will occur and how high temps will be across the region.

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The thing is though 6/6/10 wasn't really a bust...on the tornado side of it was it? I suppose so but it's not like there wasn't severe wx, there was...and a decent amount of it.

If there was no severe wx at all then you could call it a bust but just b/c there were tornado watches and no tornadoes doesn't necessarily make it a bust...just means that along with the potential for severe wx (winds/hail) storms could produce tornadoes as well.

Activity that day also became more linear rather quickly as opposed to discrete which looking back I think played a MAJOR role in the lack of tornado reports.

We'll agree to disagree. There were some wind reports but that day is a big bust IMHO. We had a lot of cloud debris and cruddy ML lapse rates. It could have been a much more widespread outbreak with higher end reports and probably a tornado or two.

There was a nice little macroburst that hit E MA that day and that one storm N of HFD, but all in all that setup definitely under performed.

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We'll agree to disagree. There were some wind reports but that day is a big bust IMHO. We had a lot of cloud debris and cruddy ML lapse rates. It could have been a much more widespread outbreak with higher end reports and probably a tornado or two.

There was a nice little macroburst that hit E MA that day and that one storm N of HFD, but all in all that setup definitely under performed.

We were in a mod risk that day and we definitely didn't live up to the definition of a moderate risk so yeah I guess it is safe to say it was a bust.

Luckily I was able to see one of the better storms that day outside of the macroburst.

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NZucker should have fun

The 12z GFS progged most of the convection well north of here, as did the 18z GFS and 18z NAM...this makes sense given that height falls are going to be better closer to the shortwave in Quebec. Also, we have due south winds tomorrow morning according to the GFS, and that may establish a marine layer near the coast which only the strongest storms could penetrate.

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The 12z GFS progged most of the convection well north of here, as did the 18z GFS and 18z NAM...this makes sense given that height falls are going to be better closer to the shortwave in Quebec. Also, we have due south winds tomorrow morning according to the GFS, and that may establish a marine layer near the coast which only the strongest storms could penetrate.

Using a model qpf forecast for a convection forecast always works well

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0z NAM doesn't show much instability at all but it's always very tough to take these model outputs face value in setups like this, especially when the number one issue is cloud cover. Looking at the soundings and wind direction in the BL I would think that we are able to clear out some...not all the clouds but we should manage some breaks. We can sit here all night and look at the models...just going to have to wait until the AM and look out the window and then satellite.

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Looks to me like heavy rain threat tomorrow, naso much severe. Models hitting CNE hard but thus far have been a bit too far north in the Midwest with the swath of heaviest rain.

Yup and that continues tonight. Bad news if you don't like cloud debris. Thankfully I'll be on Cape Coral Cod for the weekend and not have to worry about the threat bust.

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Using a model qpf forecast for a convection forecast always works well

The placement sort of makes sense, though. The shortwave is well up into Quebec which implies that NYC would not have the best height falls. There's an additional piece of energy at 500mb over NH during the daytime tomorrow, and this may serve as a focus for enhanced lift as the models show with the heavy rainfall amounts in New England. Also, we've already switched to a SE wind here at HPN, so the marine stability should curtail the development of storms here. I'm not trusting the models' QPF verbatim, but the placement makes sense.

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Looks like we may end up getting screwed today...not only b/c of potential cloud cover but too early timing, the best low-level shear and enlarged hodos don't occur until very late in the afternoon, however, models also showed that occurring on Tuesday.

If timing of storms was like 4-8 PM we'd have a much better shot.

Going to be real interesting today.

Those cloud tops with that stuff entering W. NY are pretty damn cold.

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The placement sort of makes sense, though. The shortwave is well up into Quebec which implies that NYC would not have the best height falls. There's an additional piece of energy at 500mb over NH during the daytime tomorrow, and this may serve as a focus for enhanced lift as the models show with the heavy rainfall amounts in New England. Also, we've already switched to a SE wind here at HPN, so the marine stability should curtail the development of storms here. I'm not trusting the models' QPF verbatim, but the placement makes sense.

Forecasting where convection initiates and moves is a lot more challenging than what you're suggesting here. I doubt the southeast wind at HPN at 5 a.m. is much of a clue.

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Looks like we may end up getting screwed today...not only b/c of potential cloud cover but too early timing, the best low-level shear and enlarged hodos don't occur until very late in the afternoon, however, models also showed that occurring on Tuesday.

If timing of storms was like 4-8 PM we'd have a much better shot.

Going to be real interesting today.

Those cloud tops with that stuff entering W. NY are pretty damn cold.

Models weren't even close to this impressive with the shear on Tuesday. Today's is much more impressive.

That said I'm not overly impressed but we'll see.

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Models weren't even close to this impressive with the shear on Tuesday. Today's is much more impressive.

That said I'm not overly impressed but we'll see.

Today is much more impressive no doubt, just saying they didn't really increase the shear/hodos until after 21z (was really only the 18z NAM on Monday that did this well) but helicity was up there by early afternoon.

I guess if there is something good right now despite the cloud cover temps are starting off pretty damn warm...low to mid 70's in many locations so it really won't take a great deal of sun to get temps into the 80's and for instability values to shoot to around 1000 J/KG.

Hopefully the leading edge of that line can miss us to our south and west. If this does if we can break out some sun by 11 or noon that should give us enough time to destabilize enough but we'll see. Tough call for today.

Kind of surprised though were only in 2% Tor. Thought we'd see 5% given the shear/helicity forecast.

Perhaps by 13z we will.

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