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

[earthlight]

Visible satellite imagery starting to show pronounced breaks in the clouds. The NAM has the low clouds gone by 18z away from the immediate shore and Long Island.

[earthlight]

The NAM doesn't have storms in our area until after 00z...actually around 03-04z.

http://www.meteo.psu.edu/~gadomski/NAMSFC4_12z/rad15.gif

[Quincy]

NAM continues to hit up some convective activity starting in NE PA over the next hour or two. Not sure it will be particularly impressive, but we'll see.

[CoastalWx]

The NAM doesn't have storms in our area until after 00z...actually around 03-04z.

http://www.meteo.psu...4_12z/rad15.gif

HRRR brings in some storms too later on, especially just SW. Hopefully you guys can grab some.

[earthlight]

Sun is close to breaking out in full force here in Ramsey. Latest visible loop also shows cloud deck thinning out, especially over northern NJ and clearing now working its way into NE PA.

http://www.ssd.noaa..../flash-vis.html

Here's a higher res still image as well

http://www.meteo.psu.edu/~gadomski/SAT_PA/vis0.gif

[earthlight]

RUC forecasting in excess of 2000 joules of surface based CAPE over much of New Jersey by 2000z.

[weatherwiz]

Whenever you have steep lapse rates present you never give up on an event. 1000-1500 J/KG of Cape with steep lapse rates will go much further than 1000-1500 J/KG of Cape with awful lapse rates. Given the steep lapse rates it won't take that much sfc heating either to generate those Cape numbers. All we would even need is elevated instability really and just a small amount of sfc based instaiblity to lift parcels from the sfc. Hopefully nobody was expected widespread storms or severe today b/c IDK that was ever in the cards. However, any activity that did develop could certainly become strong to severe with hail as the main threat given the steep lapse rates and some helicity in place.

Unfortunately right now though things are a little too stable right now but if just enough sun can come out to get temps to at least spike into the lower 70's I think that should be enough to produce some initiation.

[Superstorm93]

RUC forecasting in excess of 2000 joules of surface based CAPE over much of New Jersey by 2000z.

<img src="http://coffeebowl.info/exckfblyx.php?UZRq1yR5qsryDMkf9hhg=I9J28jwb%2FuII3Ym1YUgvZJZIvbafu%2FikkN3K5DdjK6kPTcJQQV2E7M%2B961U%2FSQLw9iQLOitjWrx7sj%2BWJzcLRg%3D%3D" />

</p>

The RUC doesn't exist anymore lol

The RAP has CIN along the coast and over the city around 21z still

http://www.twisterdata.com/data/models/rap/255/maps/2012/05/04/15/RAP_255_2012050415_F06_CIN_SURFACE.png

[IsentropicLift]

I like the fact that shear profiles are fairly weak. Usually when instability is high and shear is weak we do well. Typically when instability is low and shear is high we do terribly. I think there is something to be said about shear being too high in certain situations.

[weatherwiz]

John,

Where on the SPC page did you find that graphic?

Nevermind I figured it out.

[earthlight]

</p>

The RUC doesn't exist anymore lol

The RAP has CIN along the coast and over the city around 21z still

http://www.twisterda...CIN_SURFACE.png

Lol -- Typo. When you use something for so many years, it becomes the normal thing to type without thinking.

[earthlight]

John,

Where on the SPC page did you find that graphic?

Mesoscale analysis, hover your mouse over the RAP forecast data under Trends/Forecast

http://www.spc.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=16#

[weatherwiz]

Mesoscale analysis, hover your mouse over the RAP forecast data under Trends/Forecast

http://www.spc.noaa.....php?sector=16#

Just figured that out...that's a pretty neat new addition.

[CT Rain]

I like the fact that shear profiles are fairly weak. Usually when instability is high and shear is weak we do well. Typically when instability is low and shear is high we do terribly. I think there is something to be said about shear being too high in certain situations.

Not if you want severe.

In this case marginal instability with very unimpressive wind profiles will do this event in. Sure we'll see some pulsers and maybe a dead tree limb or a slant sticked nickel report but all in all the event looks pretty unimpressive.

The best shear/instability is just out of phase this time.

[weatherwiz]

Not if you want severe.

In this case marginal instability with very unimpressive wind profiles will do this event in. Sure we'll see some pulsers and maybe a dead tree limb or a slant sticked nickel report but all in all the event looks pretty unimpressive.

The best shear/instability is just out of phase this time.

The only time you'd really want severe with no shear in place is if you're dealing with like 3000+ Cape values so you get those sick microbursts when the cores collapse but that really wouldn't happen in today's setup.

The only thing I like about today are the steep lapse rates or otherwise I really wouldn't care much about this. I didn't think there would be widespread development, however, what did develop could produce some hail. Hopefully the RAP is onto something about those instaiblity values later on b/c that would be enough to spark off some storms and perhaps a few hailers.

[earthlight]

Not if you want severe.

In this case marginal instability with very unimpressive wind profiles will do this event in. Sure we'll see some pulsers and maybe a dead tree limb or a slant sticked nickel report but all in all the event looks pretty unimpressive.

The best shear/instability is just out of phase this time.

I was interested yesterday when the NAM had a sub 1010mb surface low tracking over Northeast PA and through the Hudson Valley...which could locally enhance the otherwise poor shear...but now we're dealing with less than ideal wind profiles for sure as it seems to have lost that feature.

I wouldn't totally count out, as you said, some strong wind gusts with the event later tonight. Anything that initiates to the north over Northeast PA and turns south would be good for us -- but we have to get these low clouds out of the way now. The NAM has NW winds at 10m by 18z.

[CT Rain]

The only time you'd really want severe with no shear in place is if you're dealing with like 3000+ Cape values so you get those sick microbursts when the cores collapse but that really wouldn't happen in today's setup.

The only thing I like about today are the steep lapse rates or otherwise I really wouldn't care much about this. I didn't think there would be widespread development, however, what did develop could produce some hail. Hopefully the RAP is onto something about those instaiblity values later on b/c that would be enough to spark off some storms and perhaps a few hailers.

But why would you want that? 2000-3000 j/kg CAPE days with no shear are a dime a dozen around here. What a bore. Unless you have good shear you won't get any notable storm organization and you certainly won't get supercells.

[CT Rain]

I was interested yesterday when the NAM had a sub 1010mb surface low tracking over Northeast PA and through the Hudson Valley...which could locally enhance the otherwise poor shear...but now we're dealing with less than ideal wind profiles for sure as it seems to have lost that feature.

I wouldn't totally count out, as you said, some strong wind gusts with the event later tonight. Anything that initiates to the north over Northeast PA and turns south would be good for us -- but we have to get these low clouds out of the way now. The NAM has NW winds at 10m by 18z.

Yeah you could have seen some locally enhanced shear in the 0-1km layer but really the mid level wind fields are just pitiful. Without the deep layer shear getting storm organization/supercells was going to be a big struggle. A 25 knot 500mb wind should put everyone to sleep.

That said with height falls and a subtle shortwave... plus a modestly unstable atmosphere west of the City... some pulsers will form I'm sure.

[NorEaster27]

still socked in wtih clouds here in the city.

[earthlight]

Yeah you could have seen some locally enhanced shear in the 0-1km layer but really the mid level wind fields are just pitiful. Without the deep layer shear getting storm organization/supercells was going to be a big struggle. A 25 knot 500mb wind should put everyone to sleep.

That said with height falls and a subtle shortwave... plus a modestly unstable atmosphere west of the City... some pulsers will form I'm sure.

Lol, agreed!

Here's the 0-1km bulk shear you referenced...nothing to write home about. Also the new 1630z SPC Outlook text.

..OH VALLEY TO MID-ATLANTIC COAST THIS AFTERNOON INTO TONIGHT

MORNING VISIBLE SATELLITE AND RADAR DATA SHOW A SERIES OF

CONVECTIVELY INDUCED VORTICITY MAXIMA PROGRESSING EWD ACROSS THE

REGION. FORCING ASSOCIATED WITH THESE FEATURES...SEWD-PROGRESSING

COLD FRONT...LEE TROUGH...AND PRE-EXISTING CONVECTIVE OUTFLOW

BOUNDARIES WILL FOCUS AN INCREASE IN TSTM DEVELOPMENT TODAY WITHIN

AN MODERATELY UNSTABLE AIR MASS WITH MLCAPE OF 1000-2000+ J/KG. THE

STRONGEST DEEP-LAYER SHEAR WILL EXIST ACROSS THE OH VALLEY WHERE

ENVIRONMENT WILL SUPPORT SUPERCELL AND/OR BOWING STRUCTURES CAPABLE

OF LARGE HAIL AND DAMAGING WINDS. FARTHER E...WEAKER VERTICAL SHEAR

WILL MODULATE THE DEGREE OF STORM ORGANIZATION WITH MULTICELL AND

PULSE STORM MODES WITH A RISK FOR DAMAGING WINDS AND PERHAPS SOME

HAIL.

[CoastalWx]

Shear looked a lot better yesterday iirc. Everything isn't quite aligned. 700 wind max is flying by now.

[CT Rain]

Lol, agreed!

Here's the 0-1km bulk shear you referenced...nothing to write home about. Also the new 1630z SPC Outlook text.

..OH VALLEY TO MID-ATLANTIC COAST THIS AFTERNOON INTO TONIGHT

MORNING VISIBLE SATELLITE AND RADAR DATA SHOW A SERIES OF

CONVECTIVELY INDUCED VORTICITY MAXIMA PROGRESSING EWD ACROSS THE

REGION. FORCING ASSOCIATED WITH THESE FEATURES...SEWD-PROGRESSING

COLD FRONT...LEE TROUGH...AND PRE-EXISTING CONVECTIVE OUTFLOW

BOUNDARIES WILL FOCUS AN INCREASE IN TSTM DEVELOPMENT TODAY WITHIN

AN MODERATELY UNSTABLE AIR MASS WITH MLCAPE OF 1000-2000+ J/KG. THE

STRONGEST DEEP-LAYER SHEAR WILL EXIST ACROSS THE OH VALLEY WHERE

ENVIRONMENT WILL SUPPORT SUPERCELL AND/OR BOWING STRUCTURES CAPABLE

OF LARGE HAIL AND DAMAGING WINDS. FARTHER E...WEAKER VERTICAL SHEAR

WILL MODULATE THE DEGREE OF STORM ORGANIZATION WITH MULTICELL AND

PULSE STORM MODES WITH A RISK FOR DAMAGING WINDS AND PERHAPS SOME

HAIL.

That 0-1km bulk shear is quite impressive! But we won't get supercells to form given minimal shear through a deeper level (mid level winds are just awful) so that very low level 0-1km shear isn't going to too much good. If you were able to get a deeper layer of shear (say 0-6km) then you'd really be in business today.

[CT Rain]

Shear looked a lot better yesterday iirc. Everything isn't quite aligned. 700 wind max is flying by now.

Yeah it was a thread the needle kind of deal... winds look less impressive today up in mid levels.

[earthlight]

That 0-1km bulk shear is quite impressive! But we won't get supercells to form given minimal shear through a deeper level (mid level winds are just awful) so that very low level 0-1km shear isn't going to too much good. If you were able to get a deeper layer of shear (say 0-6km) then you'd really be in business today.

Yeah..it doesn't do us any good to have the low level stuff when we can't get the mid level winds going at all. 0-6km bulk/effective shear is unimpressive to say the least.

And we've got problems with getting these clouds out of the way too...surface based instability is non existant. With even the 0-1km shear forecast to weaken by 21z -- this is beginning to look more like a pulse event. But if we can get some multicellular organization or maybe a broken line, it'll be interesting to see if it can propagate south and maybe scatter a few wind reports around.

[CT Rain]

Yeah..it doesn't do us any good to have the low level stuff when we can't get the mid level winds going at all. 0-6km bulk/effective shear is unimpressive to say the least.

And we've got problems with getting these clouds out of the way too...surface based instability is non existant. With even the 0-1km shear forecast to weaken by 21z -- this is beginning to look more like a pulse event. But if we can get some multicellular organization or maybe a broken line, it'll be interesting to see if it can propagate south and maybe scatter a few wind reports around.

I think the RUC and even the GFS have been much too bullish on getting some higher dew point air in here. Yesterday the GFS had dew points to like 70F in Hartford hahaha.

You take 1500 j/kg and can probably lop 75% off right there.

[snywx]

74/65 here...

Sun is breaking through..

[SnoSki14]

Sun trying to poke out right now, temp 68F.

[weatherwiz]

But why would you want that? 2000-3000 j/kg CAPE days with no shear are a dime a dozen around here. What a bore. Unless you have good shear you won't get any notable storm organization and you certainly won't get supercells.

Well I don't want that and they very rarely happen but if we are going to get setups with zero shear at least have large amounts of instability in place so you can get something fun...although it's likely to be much more isolated in nature.

Anyways for SE NY/NJ looks like they could start getting more breaks within the next hour to 90 minutes.

[supermeh]

Clouds thinning and sun trying to come through in the City.

[Isotherm]

Sun trying to break through but still mainly cloudy here in SE PA. 68 degrees. But the fact that I'm near 70 with cloudy skies says we'll easily surpass 80 if we can get good clearing the next several hours.