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Summer 2014 Convection/Severe Threats


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I thought this might be a good time to start such a thread. This afternoon there's a threat for isolated severe thunderstorms across northern Pennsylvania and western New York State, where an MD is up for a possible watch. Tomorrow looks like a slightly more impressive threat from central Pennsylvania up to central New York and the capital district. We're looking at stronger shear moving in and if any lingering cloud debris give way to clearing, we could see pockets of CAPE of >2500 J/kg. I could see SPC potentially upgrading the Day 2 outlook to a higher end slight with 30% probabilities, but we'll see. The NAM has been fairly consistent with a line of storms firing with perhaps a supercell structure or two before storms quickly merge into clusters or line segments.

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Fairly impressive wind fields and upper level support tomorrow for severe, although instability looks to be lagging with cloud debris and ongoing convection. IF, and this is a big if, skies could clear out even partially, given what the models are showing, this could be a potent severe weather event. As it stands now, I'd say some lines or a broken line of storms could still pose a damaging wind threat at the very least. It's something worth keeping an eye on.

Just to give an idea of the specifics, the 6z GFS was showing 40-50kts bulk shear with 100-200 m2/s2 0-3km helicity for much of the subforum. Although the 6z NAM showed somewhat less instability, it has more than twice the helicity into portions of northern PA/western NY and 45-55kts shear. While somewhat skewed due to developing a sub-998mb low, the NAM solution cannot be discounted.

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State College doesn't seem so impressed, are you still on board for tmrw Quincy?

I would think so, especially for northern PA into central NY.

NWS Binghamton had strong wording on the potential in their update earlier today:

This front has the potential to organize a significant severe weather outbreak Tuesday into Tuesday night.

The 12z NAM backed off a bit from it's overdone 6z solution, but the 12z NAM was still on board with an least an elevated severe threat. We could be talking about potential [isolated] tornadoes. If the threat ends up being a brief spinup along a line of storms or with a few widely scattered supercells remains to be seen. The expected parameters here would support at least a low-end tornado threat.
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Still on board today, but it looks like the area is coming into better focus.

Early morning observations indicate much of New York has cleared out and despite lingering clouds over western/central PA, even NWS CTP isn't concerned about that limiting instability. (Of the three NWS offices covering the area, they were the least bullish in their wording, but still at least somewhat concerned with the potential)

I think the area to watch begins in far northeast Ohio by early-mid afternoon and ramps up as it reaches the northern tier of the western half of PA, north of I-80 and closer to the NY border. Then the threat maximizes in western NY, say from Binghamton and points west. This fits nicely with climo that really seems to like the area as well for past setups.

The HRRR shows a few vigorous cells (perhaps long-lived) moving across the aforementioned area, but reaching peak intensity near and just north of the PA border in western NY.

I'd like to see visible satellite in a few hours along with the area soundings and surface obs around 9am. This will either be a high-end slight risk event with at least an isolated tornado threat, or as NWS BGM has been saying, an upgrade to moderate risk is possible. If the latter is realized, the tornado threat could indeed be increased to either a larger 5% area or perhaps 10% in the near-term as storms initiate. Damaging winds seem to be a sure bet with these storms and a few large hail reports are possible.

We'll check back in later this morning for an update and I'm also interested to see what SPC does at 13z.

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Hey Quincy, I see they broadened the 30 pct for wind damage but stuck with the 5 for TOR....I'm feeling today may be active for W/N PA and CNY. I get out of work at 1...any idea where the best place to set up would be? Our family has a well built cabin up in Coudersport, PA I'm thinking about heading up and seeing where it goes from there.

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Hey Quincy, I see they broadened the 30 pct for wind damage but stuck with the 5 for TOR....I'm feeling today may be active for W/N PA and CNY. I get out of work at 1...any idea where the best place to set up would be? Our family has a well built cabin up in Coudersport, PA I'm thinking about heading up and seeing where it goes from there.

I think that's a pretty decent starting point. I'm on my way to Binghamton now and I'll look at some more data then (1-2 hours) to see how near-term trends look. While the best parameters may be from the Ithaca to Rochester area, if any discrete cells fire in northern PA, they could easily go severe.
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MOD RISK for much on CNY and C and W PA.....45 percent wind probs and 5 percent TOR. Should be interesting.

Just saw that. Heading to Elmira for food and then probably bumping NW into the western Finger Lakes region. If you're hoping to maybe see a tornado, I would say get into NY. Somewhat better visibility and road network up there and closer to the strongest shear.
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The cell Northeast of Springville, NY might need a tor warning. Looks to be getting the classic supercell look. Velocity has been ramping up in the past few scans and cloud tops are 40k+. Should be one to watch.

Died fairly quickly as it got out of the favorable environment but is a testament to how ripe the atmosphere is to development today.

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Died fairly quickly as it got out of the favorable environment but is a testament to how ripe the atmosphere is to development today.

Agreed. It was looking very good on radar for a few scans, but once I got within about 30 miles it fell apart. Heading to Hornell to wait it out for a bit. Our time to really watch is 4-6 p.m. for any discretes ahead of the line. Even the line itself has some supercell-like structures. The concern is that those cells will likely merge over the next few hours and then we'll have lines/line segments producing more widespread damaging winds and perhaps a brief spin-up or two.
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Agreed. It was looking very good on radar for a few scans, but once I got within about 30 miles it fell apart. Heading to Hornell to wait it out for a bit. Our time to really watch is 4-6 p.m. for any discretes ahead of the line. Even the line itself has some supercell-like structures. The concern is that those cells will likely merge over the next few hours and then we'll have lines/line segments producing more widespread damaging winds and perhaps a brief spin-up or two.

 

On que nasty cell headed towards Syracuse.  Looks like your watching that cell North of Corning based off spotter network which I think is also a good play.

 

THE NATIONAL WEATHER SERVICE IN BINGHAMTON HAS ISSUED A

 

* TORNADO WARNING FOR...

  CENTRAL CAYUGA COUNTY IN CENTRAL NEW YORK...

  NORTHWESTERN MADISON COUNTY IN CENTRAL NEW YORK...

  ONONDAGA COUNTY IN CENTRAL NEW YORK...

 

* UNTIL 645 PM EDT.

 

* AT 536 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

  SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR OWASCO...

  MOVING NORTHEAST AT 50 MPH.

 

* THE STORM CAPABLE OF PRODUCING THE TORNADO WILL BE NEAR...

  SKANEATELES BY 545 PM EDT...

  MARCELLUS BY 550 PM EDT...

  ONONDAGA...TAUNTON AND CAMILLUS BY 555 PM EDT...

  SYRACUSE...WESTVALE AND NEW YORK STATE FAIRGROUNDS BY 600 PM EDT...

  LYNDON BY 605 PM EDT...

  KIRKVILLE BY 610 PM EDT...

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The Syracuse supercell likely put down a tornado or two

along its path, based upon the roof/structure damage

reports and reviewing the couplets in those areas.  It also

had some large hail to the north of the damage reports.

 

Unfortunately, more of a bookend vortex spin-up likely

occurred to the south, which has resulted in 3 fatalities.

A SVR was issued about 10-15 minutes prior to the

report.  The review of the SRV shows nothing much

until right when the comma-head reaches the damage

location, with an intense couplet.  Next scan it pretty

much disappears.  Not much could have been done

here, very sad circumstances and outcome.  The

main supercell moving through a populated area

simultaneously did not help matters.  Have to wait

for the survey to be 100% sure it was a tornado, but

the radar looks quite convincing.

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  • 2 weeks later...

interesting scenario shaping up for the next 36-48 hours, with the first impressions I am getting from the models and the analyses.

 

upstate NY, PA northern Tier, and southern/central/eastern Ontario looks like they could get strong storms and locally heavy rain due more to dynamics, south of PIT/JST/Lewistown/ABE could get the after-effects and/or assisted forcing from the potential MCS coming out of the southern Ohio Valley, and in between for most of PA, could be either feast or famine in between as who knows what in terms of boundaries and local forcing could take over.

 

going to be an interesting day tomorrow, for sure. just wonder who will be happy and who will be not so much.

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  • 1 month later...

The region could see a few isolated severe wind gusts tomorrow, anywhere from the western two-thirds of Pennsylvania into interior New York. Kind of a muddled setup that has some potential, but will probably end up being lackluster in terms of severe. The afternoon looks to feature fairly strong wind shear coupled with modest instability from W PA into C NY. Despite a fairly favorable shortwave axis and position during the peak heating, multiple lines of showers/weak convection may ultimately rob the atmosphere of the juices needed for a more substantial threat. Models hint at a primary line of convection just ahead of the cold front with at least a heavy rain potential. Also, a pre-frontal trough may swing into eastern New York in the an even lesser "threat."

If conditions were to clear out more than currently anticipated, there could be some clusters/semi-discrete cells that develop, posing a severe wind and brief hail (probably sub-severe) threat. If a well-defined surface low does form across western NY, there could be enough low-level shear to support a marginal tornado threat.

Again, there are many IFs with this setup and I think more likely than not, we won't see anything widespread or significant tomorrow.

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