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Spring/ Summer 2014 Convection Discussion


weatherwiz

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With that said, as for Tuesday, I am shocked we don't see at least 5% probs in place

 

Yeah, that was the reason why I posted the SPC map for Tuesday.  Seems like they went from one extreme to the other.

 

I'm sure they'll update as we get closer though.

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Yeah, that was the reason why I posted the SPC map for Tuesday.  Seems like they went from one extreme to the other.

 

I'm sure they'll update as we get closer though.

 

Unless something horrible happens with 0z runs tonight I would think we see at least a SEE TEXT introduced and maybe even a slight...although that could wait until the 1730 outlook tomorrow

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I also wouldn't rule out a strong or severe storm in western MA or western CT tonight between 9 PM and midnight

Watching a couple of semi-discrete cells in NE PA. Given the downstream environment, could see a severe threat extend into at least SE NY. Perhaps the areas you mentioned this evening with at least some elevated instability.
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Watching a couple of semi-discrete cells in NE PA. Given the downstream environment, could see a severe threat extend into at least SE NY. Perhaps the areas you mentioned this evening with at least some elevated instability.

 

WE'll see how fast they work in and how quickly we hold onto the instability.  Looks like we'll get up to 1500 Cape up to the NY/CT border but begins to diminish quickly after sunset.  Shear will be increasing though so could compensate some

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Gotta remember the SPC is in place more for large scale and widespread severe weather events as opposed to more localized threats or localized setups...those events/setups the local WFO's will usually carry much more weight.  

 

With that said, as for Tuesday, I am shocked we don't see at least 5% probs in place, however, for tomorrow I have no problems with how they are handling the situation.  Given the consistency/agreement within the guidance of us seeing at least 1500 J/KG of SBcape and perhaps as much as 1000 J/KG of MLcape, they feel that was significant enough when coupled with the shear to extend the slight risk into SNE.  

 

 

I wonder what their in-house sort of "non-discrete" (no pun intended...) policy is for different sectors of the country.  I mean, it seems the perceived "they miss NE" may really just be a function of their prioritization, derived from statistical occurrence.   

 

Think about that for a moment; if they know they are not going to be right all the time, it may not be in the best interest of their credibility to flag NE ...3 days out for convection.  Not based on past performance, no way!  NE's threats seem to come by a single model run and don't hold. That also makes it harder.  I'd say they'd miss NE for over-forecasting if they did, which we all know that over-prediction is far worse for public perception.  

 

Bottom line ... I have seen more SLGHT regions hashed out for us at the last minute than those predicted for D2, enough so to wonder if that is done deliberately for some reason.   They probably have no compunctions about expanding a narrow corridor of 5 or even 15% if they need to, rather than getting NE to learn to ignore "threats" all together.  interesting

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I wonder what their in-house sort of "non-discrete" (no pun intended...) policy is for different sectors of the country.  I mean, it seems the perceived "they miss NE" may really just be a function of their prioritization, derived from statistical occurrence.   

 

Think about that for a moment; if they know they are not going to be right all the time, it may not be in the best interest of their credibility to flag NE ...3 days out for convection.  Not based on past performance, no way!  NE's threats seem to come by a single model run and don't hold. That also makes it harder.  I'd say they'd miss NE for over-forecasting if they did, which we all know that over-prediction is far worse for public perception.  

 

Bottom line ... I have seen more SLGHT regions hashed out for us at the last minute than those predicted for D2, enough so to wonder if that is done deliberately for some reason.   They probably have no compunctions about expanding a narrow corridor of 5 or even 15% if they need to, rather than getting NE to learn to ignore "threats" all together.  interesting

 

Obviously all speculation on my part but when dealing with the case of the D6 area we saw this is what I think happened...

 

At the time the outlook was issued...there was not only run-to-run consistency but very good agreement that our region would have a great overlap of modest instability and very strong shear.  That signal was quite clear and with that they felt that was enough to warrant a D6 outlook (which as you know is equal to 30% probs).  

 

However, with new data and passing days some of the signals started to become a little more questionable, virtually with regards to timing of important features.  You can tell though their confidence isn't as high as we have not seen any 30% probs issued with any of the outlooks...although I do think we will see some with the new day 1 tonight or with the 13z outlook tomorrow.  

 

When it comes to severe here (as you know) it's a much different game than other parts of the country and you need to have a much better idea of climo and mesoscale factors when it comes to severe here and probably at the SPC they don't have that luxury b/c they don't live here...it's not a knock on them...the only way to really have an understanding is to live and experience it first hand...this is why I think at times it seems they struggle here.  

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Bottom line ... I have seen more SLGHT regions hashed out for us at the last minute than those predicted for D2, enough so to wonder if that is done deliberately for some reason. They probably have no compunctions about expanding a narrow corridor of 5 or even 15% if they need to, rather than getting NE to learn to ignore "threats" all together. interesting

Interesting thoughts to ponder about "ignoring" threats...

From an operational viewpoint, I think at least some of it has to do with the question on cloud-cover/debris affecting instability, which are often not resolved until the near-term up here.

Local meteorologists and enthusiasts up here also know that it's typically the "low-end" threats that result in the bigger events, including tornadoes. Mesoscale forcing from our unique topography and proximity to the coastline can skew results.

Consider that nationally, here are the middle ground thresholds for significant severe thunderstorms, meaning the average parameters in place for discrete supercells:

MLCAPE: 1980 J/kg

EBWD: 49kts

ESRH: 223 m2/s2

Whereas using SPCs environmental browser for the NW CT/SW MA grid point, the thresholds are lower...

MLCAPE: 1421 J/kg

EBWD: 44kts

ESRH: 138 m2/s2

This changes even more when looking at different convective modes, as the Northeast sees less discrete supercells by comparison to the Plains/Midwest.

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Sorry in advance for the probable dumb question, but is cloud cover and convective debris as much an inhibitor to thunderstorm development in other parts of the country as it always seems to be around here in SNE? Can it be more easily overcome in other regions?

 

It can be a problem across other parts of the country but what really helps with that is having an EML in place or an EML advect in.  What leads to it being a major issue here is we usually always have crappy lapse rates and a saturated atmospheric column.  

 

It can be overcome and from various ways...dry air advecting in the mid levels (which may actually occur tomorrow), the sun burning off the clouds, downsloping flow.  

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Sorry in advance for the probable dumb question, but is cloud cover and convective debris as much an inhibitor to thunderstorm development in other parts of the country as it always seems to be around here in SNE? Can it be more easily overcome in other regions?

 

Actually not a bad question at all...   They answers are yes and yes.   

 

New England gets favorable deep layer mechanics from time to time .. .but, they don't have a source region like the Gulf of Mexico lurking SE, where/when retreating highs quickly load higher CAPE air into a region that experiences favorable mechanics as an almost defacto condition.

 

Sun/diabatic heating always helps everywhere... But with cloud contamination, the other factors take over, and t-alley just have these in abundance.  

 

Just keep in mind, tornadoes, even big one happen up this way. It's a matter of relative infrequence

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There's a defused warm boundary being initialized that situates from NW NYS to roughly ALB and it appears these cells are tapping into the SRS along that boundary to acquire torsion.   They are really moving almost parallel to the boundary and just to the S... 

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Finished

mcd1358.gif

 

MESOSCALE DISCUSSION 1358
NWS STORM PREDICTION CENTER NORMAN OK
0449 PM CDT SUN JUL 13 2014

AREAS AFFECTED...S NY...WRN MA/CT...CNTRL/E PA...N NJ

CONCERNING...SEVERE THUNDERSTORM WATCH 414...

VALID 132149Z - 132315Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 414
CONTINUES.

SUMMARY...PRIMARY SEVERE RISK IN THE FORM OF ISOLATED DAMAGING WINDS
WILL MAINLY PERSIST NEXT FEW HOURS WITHIN WW 414 ACROSS PARTS OF PA
AND S NY. NRN PORTION OF STORM CLUSTER WILL ALSO POSE A THREAT FOR A
BRIEF TORNADO...WITH PROBABILITY OF DOWNSTREAM WW ISSUANCE AROUND 50
PERCENT THROUGH 23Z.

DISCUSSION...MOST INTENSE STORM IN REFLECTIVITY/VELOCITY DATA EXISTS
ON THE NE CORNER OF WW 414 OVER SULLIVAN COUNTY. THIS SUPERCELL IS
BEING FED BY UPPER 60S TO LOWER 70S SURFACE DEW POINTS AMIDST A
VEERING LOW-LEVEL HODOGRAPH CHARACTERIZED BY 0-1 KM SHEAR OF 25-30
KT PER BGM/ENX/OKX VWP DATA. ALTHOUGH THIS CELL HAS WEAKENED
SOMEWHAT OVER THE PAST 15 MIN...WITH SURFACE TEMPERATURES APPEARING
WARMER THAN FORECAST BY GUIDANCE...AN ISOLATED SEVERE RISK SHOULD
EXIST FOR THE NEXT FEW HOURS ACROSS PARTS OF THE HUDSON VALLEY INTO
SW NEW ENGLAND.

FARTHER W...BROKEN LINE OF STORMS FROM SW NY INTO W PA SHOULD TRACK
A BIT S OF E THROUGH THE EVENING...MAINLY AFFECTING PORTIONS OF PA.
MODERATE DEEP-LAYER WLYS IN AREA VWP DATA WILL REMAIN SUPPORTIVE OF
ISOLATED DAMAGING WINDS.

..GRAMS.. 07/13/2014

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Isnt he like 16 now living in British Columbia? Tons of severe there

 

I'm in university, nice detective work Rust.

 

Also I love how you think me living somewhere else where there isn't much severe suddenly makes me unworthy to discuss the topic, that's as rich as Bill Gates. At least I won't have any fakenadoes to see out my backdoor.

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