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Severe Weather possible weekend of the 21st?


weatherwiz

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FRIDAY INTO SATURDAY...

UPPER LEVEL LOW OVER HUDSON BAY WILL PUSH A BROAD TROUGH OVER THE
GREAT LAKES REGION. THIS WILL ALLOW FOR THE REGION TO BE IN A
POSSIBLE PRIME LOCATION FOR SEVERE WEATHER POTENTIAL. AS THE REGION
IS ALREADY IN A MOIST HUMID AIRMASS AND THE INSTABILITY WILL BE HIGH
AS WELL. A COLD FRONT DROPPING DOWN FROM CANADA WILL BE THE DRIVING
OR LIFT FACTOR FOR POSSIBLE CONVECTION DEVELOPMENT. CONFIDENCE IS
HIGH THAT HEAVY DOWNPOURS WILL BE ONE OF THE MAIN THREATS SO HAVE
ADDED THE ENHANCED WORDING INTO THE FORECAST. HOWEVER THIS IS STILL
SEVERAL DAYS OUT SO WE WILL NEED TO CONTINUE TO MONITOR THE LATEST
GUIDANCE TO SEE IF THE POTENTIAL CONTINUES.

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Beyond the obvious ML lapse rates, one of the underrated benefits of the EML is the initial CIN and tendency to keep things discrete at first.  It's pretty hard out here to give a supercell room to breathe for an extended period without going quasi linear and choking everything off.  

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Beyond the obvious ML lapse rates, one of the underrated benefits of the EML is the initial CIN and tendency to keep things discrete at first.  It's pretty hard out here to give a supercell room to breathe for an extended period without going quasi linear and choking everything off.  

CIN should be fairly weak this upcoming Saturday so I think things should fire up fairly quickly rather than having to wait. I just hope my area gets something good for once. It'd be nice to remember this summer for something other than dew points.

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we need eml advection... just looked at gfs bufkit and lapse rates stink this week

yeah, that's one thing we have seen with these ridge episodes this year, and that's a well time plateau air mass ejection that gets absorbed into the ridge where it rattles around and drive temps to 100 and beyond -- if we got some of that, it would make the approach of dynamics more interesting. 

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ZCZC SPCSWOD48 ALL
ACUS48 KWNS 150813
SPC AC 150813

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0313 AM CDT MON JUL 15 2013

VALID 181200Z - 231200Z

...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.

..EDWARDS.. 07/15/2013

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With the exception of one decent storm at the end of May, the severe season has been numbingly boring in Franklin County.  Could be worse, we could be in the midst of a deadly drought of epic proportions.  Oh wait, that was April.  :)

Severe has been numbingly boring everywhere in MA, except if you live in Danvers, MA or Stoughton, MA.

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 I'm not a discrete snob, will take a squall line or mcs/mcc any day.

 

I prefer the term connoisseur lol.

 

At least out here the squall lines always seem to peter out as they descend the east slope and hit the river.   You can pretty much count on a cool looking shelf, 30kts along the gust front, decent size droplets falling not too hard and if you're lucky maybe a few stray peas at the height before it washes through. 

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Beyond the obvious ML lapse rates, one of the underrated benefits of the EML is the initial CIN and tendency to keep things discrete at first.  It's pretty hard out here to give a supercell room to breathe for an extended period without going quasi linear and choking everything off.  

 

Absolutely. This is really key. Look at 6/1/11... that supercell along the Mass Pike had a clear area of nasty inflow to the south with no junk in CT messing it up. 

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Absolutely. This is really key. Look at 6/1/11... that supercell along the Mass Pike had a clear area of nasty inflow to the south with no junk in CT messing it up. 

 

Yeah exactly.  And the flip side were the supercells to the north, the first in Ashfield, the second near Northampton, that both might have gone tornadic with a continued feed of moist air. 

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Yeah exactly.  And the flip side were the supercells to the north, the first in Ashfield, the second near Northampton, that both might have gone tornadic with a continued feed of moist air. 

 

It was sort of a perfect storm too. The cap/EML helped suppress activity to the south and provided a clean channel for high theta-e air to race north. At the same time to the north where the cap had broken you had 2 separate supercells that were sending out some outflow boundaries that probably helped enhance SRH locally and maintained the tornadic circulation. 

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I was some numbers for the afternoon of June 1st near Springfield and wow, those are the highest combined values I've seen up in this part of the country...

STP: 3.01
SCP: 22

MLCAPE: 2500

EBS: 48

SRH: 400

ML LCL: 1000

 

4.22 (very high) on a scale of 0 to 5 for tornado probability. ("Q-tor")

I'll say this before, a 5 (extreme probability) is only theoretical if each of the variables above were maxed out near climatoligcal highs.

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The lapse rates do kinda suck for what generally speaking is a good severe mcs set up.  The lack of troughing in the west is cutting off the real low/mid-level warmth in the plains and the intermountain west from making good process east.  How often do you see 600dm ridges in july in ohio with only 18 to maybe 19c 850s?  

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CORRECTED IMAGE...as mentioned below, I had the wrong month for 2011.

 

Here is June 1st (not July 1st), 2011 and ML LR's according to this SPC re-analysis were near or just over 7.5°C/km in south-central Massachusetts:
19_laps.gif

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