7/19 - 7/21 Severe Threat

[user13]

Euro and GFS have been in agreement for a few days regarding organized convective activity in the area this weekend. With a potent cold front approaching, this could be one of our best opportunities to see a wide spread outbreak this summer.

[user13]

SPC:

...DISCUSSION...

PATTERN FCST TO BECOME FAVORABLE FOR CORRIDORS OF ENHANCED SVR

POTENTIAL BETWEEN UPPER MIDWEST AND MID-ATLC/NEW-ENGLAND REGION.

THIS MAY INCLUDE SWATH OF DAMAGING WIND ON ONE OR MORE DAYS WITHIN

DAY-4 TO DAY-6 TIME FRAME...AND RELATIVELY DENSE DIURNAL

CONCENTRATIONS OF MULTI-MODAL SVR CONVECTION OTHERWISE. TO SOME

EXTENT...SVR THREATS ON DAYS 5-6 DEPEND ON EACH DAY PRIOR...HOWEVER

GIVEN OVERALL FAVORABLE PATTERN AND PROBABILITY OF STG BUOYANCY IN

PRECONVECTIVE AIR MASS...WILL MAINTAIN 30% AREAS FROM PREVIOUS FCST

WITH ONLY MINOR ADJUSTMENTS. BEYOND THAT...POTENTIAL BECOMES TOO

CONDITIONAL FOR OUTLOOK. OPERATIONAL SPECTRAL/ECMWF...AS WELL AS

ENSEMBLES OF EACH...HAVE BECOME REMARKABLY CONSISTENT WITH EACH

OTHER AND FROM RUN TO RUN WITH PATTERN EVOLUTION DISCUSSED BELOW.

IN MID-UPPER LEVELS...ANOMALOUS COLD-CORE CYCLONE NOW OVER OK WILL

MOVE SWWD TO SONORA AND GET ABSORBED INTO BROADER SUBTROPICAL

TROUGHING BY DAY-4/18TH-19TH. RIDGING WILL DOMINATE MOST OF CONUS

TO ITS N AND NE...EXCEPT FOR CORRIDOR FROM NRN PLAINS ACROSS GREAT

LAKES TO NEW ENGLAND. EXPECT INCREASE IN CYCLONIC CURVATURE AND

STRENGTH OF FLOW OVER THAT BELT DAYS 4-7 WITH ACCOMPANYING SEWD

MOVEMENT OF SEASONALLY STG COLD FRONT. FAVORABLE LOW-LEVEL MOISTURE

IS ALREADY IN PLACE OVER MUCH OF MIDWEST/NERN STATES AND SHOULD

REMAIN SO PRIOR TO FROPA OR MCS USAGE. AS CYCLONE NOW OVER GULF OF

AK DIGS SWD...PORTION OF INITIALLY CUT-OFF LOW OFFSHORE CA WILL

EJECT NEWD THROUGH MEAN RIDGE OVER PAC NW AND BC DAY-3...THEN ESEWD

ACROSS SRN PRAIRIE PROVINCES TO NRN MN DAY-4/18TH-19TH. SFC

CYCLOGENESIS OVER DAKOTAS AND RESULTING MASS RESPONSE BENEATH SRN

RIM OF FAVORABLE WNW FLOW ALOFT SHOULD CONTRIBUTE TO SVR THREAT

INCLUDING SUPERCELL RISK...POTENTIALLY EVOLVING UPSCALE INTO MCS

OVERNIGHT AND MOVING EWD ALONG BAROCLINIC ZONE INTO UPPER GREAT

LAKES REGION.

SYNOPTIC AMPLIFICATION ALOFT AND PERHAPS OUTFLOW SHOULD SHUNT

LOW-LEVEL FRONTAL ZONE AND CORRIDOR OF ORGANIZED SVR THREAT SWD

DAY-5/19TH-20TH INTO VERY MOIST AND LIKELY HIGH-CAPE AIR MASS...WITH

MID-UPPER WINDS NEARLY PARALLEL TO FRONTAL ZONE OVER MUCH OF AREA.

CONTINUED MID-UPPER AMPLIFICATION/SWD SHIFT OF CYCLONIC FLOW ALOFT

SHOULD OCCUR DAY-6/20TH-21ST...WITH SVR THREAT SHIFTED ACCORDINGLY

EWD AND SEWD. ANY ORGANIZED SVR-WIND EVENT THAT DEVELOPS MAY

OVERLAP PARTS OF TWO OUTLOOK-DAYS.

[IsentropicLift]

Reminds me an awful lot of the pattern that setup before the big Mid-West to Mid-Atlantic derecheo last year. It was over 100 degrees that day if I remember correctly.

 

The 00z GGEM had several waves of precip impacting the area beginning at hr 144 and continuing through day 10.

[user13]

SPC:

  ...D5/SAT...   A CONTINUATION OF THE ORGANIZED SEVERE WEATHER THREAT WILL SPREAD   EAST ACROSS THE NORTHEAST ON SAT. UPPER TROUGH WILL CONTINUE TO   DEEPEN/AMPLIFY WITH A SHARP FRONTAL ZONE ADVANCING EWD/E-SEWD INTO   INCREASINGLY UNSTABLE AIRMASS DURING THE DAY. AFTER A LULL IN MORE   WIDESPREAD SEVERE WEATHER THREAT FROM LATE FRIDAY NIGHT INTO   SATURDAY MORNING...STORMS WILL INCREASE IN COVERAGE AND INTENSITY AS   PRE-FRONTAL AIRMASS DESTABILIZES. LINE SEGMENTS ALONG AND AHEAD OF   THE FRONT WILL AGAIN POSE A THREAT FOR DAMAGING WINDS FROM THE ERN   GREAT LAKES TO NEW ENGLAND AND SOUTH TO THE UPPER OH VALLEY AND   DELMARVA REGION. SHEAR/FORCING WILL BE WEAKER WITH SWD/SWWD EXTENT   ALONG THE FRONT BUT MAY BE COMPENSATED TO SOME EXTENT BY DEGREE OF   POTENTIAL DESTABILIZATION. COLD FRONT SHOULD MOVE ACROSS THE   NORTHEAST U.S. COAST DURING SUNDAY MORNING.

[ag3]

0z euro has good timing with the front on it's latest run. Brings it through NYC from 2pm to 8pm on Saturday.

[earthlight]

Good wind fields and tons of instability with a well timed front. My main concern with these events is always the lapse rates, which for the most part have had a tendency to be crap over the last 5 years or so in every event. So we will have to see how the models handle it as we draw closer.

We saw last year how we can get screwed even despite a well timed front, good wind fields and high instability. 4000 joules of cape went to nothing last year because of bad lapse rates and the storms outrunning the best forcing. If we see that again, we'll be watching a big line in Central PA collapsing to garden variety storms redeveloping on their own gust fronts.

We will see.

[easternsnowman]

Much rather have excessive heat instead of severe junk!

[SnoSki14]

Much rather have excessive heat instead of severe junk!

 

That's your opinion, but I can't stand this heat, though it's mostly the oppressive humidity that's been unbearable. I'll be happy once we get past the worst heat of the year and finally start to cool down even a little bit. We're right around the peak heat of the year and soon the days will be getting noticeably shorter and the averages will start to tick down. 

Good wind fields and tons of instability with a well timed front. My main concern with these events is always the lapse rates, which for the most part have had a tendency to be crap over the last 5 years or so in every event. So we will have to see how the models handle it as we draw closer.

We saw last year how we can get screwed even despite a well timed front, good wind fields and high instability. 4000 joules of cape went to nothing last year because of bad lapse rates and the storms outrunning the best forcing. If we see that again, we'll be watching a big line in Central PA collapsing to garden variety storms redeveloping on their own gust fronts.

We will see.

 

That's honestly what I'm expecting it to happen. It'll look really good over PA and then as soon as it crosses into NJ it'll fall apart. I haven't seen true severe weather in years around here. This year has been pathetic so far, a few rumblings, a few lightning strikes but nothing memorable. 

[user13]

Good wind fields and tons of instability with a well timed front. My main concern with these events is always the lapse rates, which for the most part have had a tendency to be crap over the last 5 years or so in every event. So we will have to see how the models handle it as we draw closer.

We saw last year how we can get screwed even despite a well timed front, good wind fields and high instability. 4000 joules of cape went to nothing last year because of bad lapse rates and the storms outrunning the best forcing. If we see that again, we'll be watching a big line in Central PA collapsing to garden variety storms redeveloping on their own gust fronts.

We will see.

Yea lately we always seem to get into the blow offs and even though its far out the 0z Euro has the blow off getting to us way ahead of the storms again

 

-06 GFS had pop up storms on Thursday and Friday as well, so we should have a few chances

[mupawxnut]

Good wind fields and tons of instability with a well timed front. My main concern with these events is always the lapse rates, which for the most part have had a tendency to be crap over the last 5 years or so in every event. So we will have to see how the models handle it as we draw closer.

We saw last year how we can get screwed even despite a well timed front, good wind fields and high instability. 4000 joules of cape went to nothing last year because of bad lapse rates and the storms outrunning the best forcing. If we see that again, we'll be watching a big line in Central PA collapsing to garden variety storms redeveloping on their own gust fronts.

We will see.

Are you referring to 7/26/2012?

[Stormlover74]

Are you referring to 7/26/2012?

That would be the day

[jm1220]

That's your opinion, but I can't stand this heat, though it's mostly the oppressive humidity that's been unbearable. I'll be happy once we get past the worst heat of the year and finally start to cool down even a little bit. We're right around the peak heat of the year and soon the days will be getting noticeably shorter and the averages will start to tick down. 

 

That's honestly what I'm expecting it to happen. It'll look really good over PA and then as soon as it crosses into NJ it'll fall apart. I haven't seen true severe weather in years around here. This year has been pathetic so far, a few rumblings, a few lightning strikes but nothing memorable. 

Yep. As others have mentioned, we rarely do well when storms blow up hundreds of miles west and progress east. I'm not a fan of over 90F heat, so it will be refreshing to have cool weather again.

[earthlight]

Some of the medium range model guidance had hints of a remnant eml or at least moderately favorable mid level lapse rates. The latest sref has a 10 % chance of mid level lapse rates over 7.

 

http://www.spc.noaa.gov/exper/sref/gifs/latest/SREF_prob_H7_to_H5_LapseRate_7__f087.gif

 

Given the environment otherwise, I think mid level lapse rates over 6.5 could be okay. But obviously the general idea on the models is that the mid level lapse rates won't be as spectacular as some of the other features lining up, namely the instability and favorable wind fields.

[tmagan]

I think the term is used too much, but I can see a 'derecho' in the northeast from this.

[Weathergun]

The GFS has 6.5-7 C/km 700-500mb lapse rates. But were are between two 850mb jet streaks, Saturday afternoon. Which may limit shear and forcing in our area. Especially further south and east:

 

[IsentropicLift]

The analog guidance is hinting at 30% for wind near the region on Saturday.

 

PPF24windprobtopgfs212F096.png

SPC has maintained our region in a day 4 severe outlook which equates to 30% prob. We have been in a day 7, day 6 and day 5 risk consecutively. Hard to remember the last time that happened.

 

[user13]

SPC has maintained our region in a day 4 severe outlook which equates to 30% prob. We have been in a day 7, day 6 and day 5 risk consecutively. Hard to remember the last time that happened.

 

SPC:

VIGOROUS/SEVERE TSTMS CAN BE EXPECTED AS LIFT ALONG THE FRONTAL ZONE   ACTS ON VERY WARM AND MOIST AIR FROM OH TO NEW ENGLAND DURING THE   DAY SAT. STRENGTHENING WIND FIELDS WILL SUPPORT BANDS OR LINES OF   STORMS SPREADING ESEWD WITH DAMAGING WINDS BEING THE PRIMARY SEVERE   WEATHER HAZARD.

[user13]

4k Sim has one long line of storms there.

- It has another MCS coming through on Friday

[bluewave]

The Euro looks really active for Saturday. It may start out severe and evolve into the potential

for localized flooding where training sets up along the trailing end of the cold front.

 

[IsentropicLift]

18z NAM has basically a thin squall line that dies out as it hits the coast. It also gets temps into the 90's for much of the area before the precip arrives.

[SnoSki14]

I'm thinking more localized flooding than severe. I have a hard time believing we're gonna see severe weather. Those in more typical spots probably will (Central/Eastern PA, upstate NY, NW NJ, but those to the E/SE will probably get the scraps/junk storms.

[IsentropicLift]

The 18z 4k NAM simulated radar for early Saturday morning has a potent look to it.

 

[Superstorm93]

For the NYC metro, Saturday really doesn't seem like a setup that holds too much severe potential (I don't even think that there is a setup that ever does for the region) 

 

The bulk of the wind reports on Saturday should be in east/central Pennsylvania, upstate New York, and possibly NW NJ. 

 

Last severe thunderstorm here was over four years ago and I don't think that going to change anytime soon. 

[BxEngine]

For the NYC metro, Saturday really doesn't seem like a setup that holds too much severe potential (I don't even think that there is a setup that ever does for the region)

The bulk of the wind reports on Saturday should be in east/central Pennsylvania, upstate New York, and possibly NW NJ.

Last severe thunderstorm here was over four years ago and I don't think that going to change anytime soon.

Huh? There is zero chance the last severe storm in the Upton area was 4 years ago.

[mob1]

Huh? There is zero chance the last severe storm in the Upton area was 4 years ago.

He meant a widespread legitimate verified severe weather event, we came up 1 EML short last year as the storms outran the best forcing and we had meh lapse rates.

[bluewave]

He meant a widespread legitimate verified severe weather event, we came up 1 EML short last year as the storms outran the best forcing and we had meh lapse rates.

 

The last few years have been some of the most active on record for severe around here. Breezy Point and Islip

Tornadoes last summer. Three inch diameter record breaking hailstones on Long Island during August 2011 and

the NYC Macroburst and tornado in 2010. An west to east raker Derecho ala Labor Day 1998 is always

the exception rather than the rule. If people want the classic MDT or High Risk they will have to move west.

[mob1]

The last few years have been some of the most active on record for severe around here. Breezy Point and Islip

Tornadoes last summer. Three inch diameter record breaking hailstones on Long Island during August 2011 and

the NYC Macroburst and tornado in 2010.

But all those were relatively isolated and confined to portions of the city (I believe superstorm is from NE NJ) Good point about how rare widespread events are though, the 98 labor day derecho is the only one I remember. (on a more positive note, my area was hit with an EF1 in 2007)

[IsentropicLift]

After riding out the Mid-Atlantic derecho last year in an RV, I have to say severe weather isn't all it's cracked up to be.

[bluewave]

But all those were relatively isolated and confined to portions of the city (I believe superstorm is from NE NJ) Good point about how rare widespread events are though, the 98 labor day derecho is the only one I remember. (on a more positive note, my area was hit with an EF1 in 2007)

 

Well yeah, widespread events are always less common here. But each of the last few years provided several firsts orvery rare events at different locations around the area. I think that people try to compare an active severe

thunderstorm day here to what happens in the Plains or Midwest.

[ag3]

After riding out the Mid-Atlantic derecho last year in an RV, I have to say severe weather isn't all it's cracked up to be.

Queens, specifically Northern Queens, experienced an EF1 tornado AND a 125mph macroburst with the same storm in September of 2010.

The damage I saw around Flushing/Bayside was remarkable and I doubt any storm ever does that type of damage again in this area.