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May 2011 NYC metro area obs./discussion


tmagan

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MESOSCALE DISCUSSION 0809

NWS STORM PREDICTION CENTER NORMAN OK

0947 AM CDT THU MAY 19 2011

AREAS AFFECTED...PARTS OF CENTRAL/ERN NY...ERN PA...AND CENTRAL/NRN

NJ

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 191447Z - 191615Z

SEVERE TSTM WATCH ISSUANCE MAY BE NEEDED BY EARLY AFTERNOON ACROSS

PARTS OF ERN PA...NRN NJ INTO PORTIONS OF CENTRAL AND ERN NY. HAIL

IS EXPECTED TO BE THE PRIMARY THREAT.

A SLIGHT RISK AREA WILL BE ADDED TO THE DAY 1 CONVECTIVE OUTLOOK FOR

THIS MESOSCALE DISCUSSION AREA.

VISIBLE SATELLITE IMAGERY SHOWED BREAKS IN CLOUDINESS ACROSS NORTH

CENTRAL-NERN PA...NJ AND INTO MUCH OF NY...WITH SURFACE HEATING ALSO

EXPECTED IN THE WAKE OF CONVECTION CURRENTLY TRACKING NWD THROUGH

SRN/CENTRAL NY. OBJECTIVE ANALYSES SHOWED THE AIR MASS FROM

DELMARVA/MID ATLANTIC REGION NWD INTO NY DESTABILIZING /MUCAPE

500-1000 J/KG/...GIVEN SURFACE HEATING BENEATH MIDLEVEL LAPSE RATES

CLOSE TO 7 C/KM. ALTHOUGH MIDLEVEL WINDS SHOULD TEND TO WEAKEN WITH

THE APPROACH THE MIDLEVEL CLOSED LOW FROM THE UPPER OH VALLEY...

EFFECTIVE BULK SHEAR OF 25-30 KT WILL BE SUFFICIENT FOR MULTICELLS

AND LINE SEGMENTS. FORCING FOR ASCENT ATTENDANT TO A MIDLEVEL

IMPULSE TRACKING NWD FROM ERN VA AND THE CLOSED LOW ITSELF IS

EXPECTED TO SUPPORT NEW TSTM DEVELOPMENT ACROSS ERN PA BY EARLY

AFTERNOON...WITH ACTIVITY SPREADING INTO NJ AND PARTS OF CENTRAL/ERN

NY. COLD MIDLEVEL TEMPERATURES PER AREA 12Z SOUNDINGS /-18 TO -20 C

AT 500 MB/ ADVECTING OVER THIS REGION AND STEEPENING LAPSE RATES

WILL SUPPORT HAIL AS THE PRIMARY SEVERE WEATHER THREAT.

11Z WRF-HRRR AND 00Z 4 KM WRF-ARW/WRF-NMM SUPPORT THE CONVECTIVE

SCENARIO SHOWING ONE OR MORE CLUSTERS/BROKEN LINES OF CONVECTION

DEVELOPING OVER ERN PA AND SPREADING INTO NJ/NY.

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The 12z GFS gives everyone in NJ around an inch more of rain through 48hrs and east of that around a half inch with amounts decreasing as you move east. Looks like the threat for training will be higher today and situated over NJ and PA which means most everyone in this sub-forum won't care. :P

Today's 12z GFS does not give anyone in NJ an inch of rain through 48 hours. I'm not sure which model you're looking at. Again with the illusions. Below is the 60 hour total from today's 12z GFS, ending Saturday night. Blue shade is .50-.75"... an inch is only bullseyed over northeastern PA, and western New England. whistle.gif

post-705-0-66523500-1305821558.jpg

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Today's 12z GFS does not give anyone in NJ an inch of rain through 48 hours. I'm not sure which model you're looking at. Again with the illusions. Below is the 60 hour total from today's 12z GFS, ending Saturday night. Blue shade is .50-.75"... an inch is only bullseyed over northeastern PA, and western New England. whistle.gif

shocker, he exagerated something.

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SEL7

URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 307

NWS STORM PREDICTION CENTER NORMAN OK

1220 PM EDT THU MAY 19 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

CENTRAL AND NORTHERN NEW JERSEY

SOUTHERN TIER OF NEW YORK

EASTERN PENNSYLVANIA

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 1220 PM UNTIL

800 PM EDT.

HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70

STATUTE MILES EAST AND WEST OF A LINE FROM 55 MILES NORTHEAST OF

BINGHAMTON NEW YORK TO 30 MILES WEST SOUTHWEST OF PHILADELPHIA

PENNSYLVANIA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.

DISCUSSION...THUNDERSTORMS WILL CONTINUE TO DEVELOP WITHIN A

DESTABILIZING AIR MASS ACROSS ERN PA AND SPREAD INTO NJ AND PARTS OF

SRN AND SERN NY THIS AFTERNOON AND EARLY EVENING. MULTICELLS

PRODUCING SEVERE HAIL AND STRONG WIND GUSTS WILL THE PRIMARY

THREATS.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 400. MEAN STORM

MOTION VECTOR 20020.

...PETERS/IMY

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Today's 12z GFS does not give anyone in NJ an inch of rain through 48 hours. I'm not sure which model you're looking at. Again with the illusions. Below is the 60 hour total from today's 12z GFS, ending Saturday night. Blue shade is .50-.75"... an inch is only bullseyed over northeastern PA, and western New England. whistle.gif

when I see a broad area of around 0.75" on the GFS I bump it up just a hair to account for the lower resolution. Not really sure why it matters though, its generally a terrible model to use for short term QPF. Sure there are days that it does a good job and then you get days like yesterday where none of the models did a very good job on picking it up. And before a smart one on here says that I'm wrong about none of the models doing a good job yesterday, that came right from Upton's AFD yesterday.

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when I see a broad area of around 0.75" on the GFS I bump it up just a hair to account for the lower resolution. Not really sure why it matters though, its generally a terrible model to use for short term QPF. Sure there are days that it does a good job and then you get days like yesterday where none of the models did a very good job on picking it up. And before a smart one on here says that I'm wrong about none of the models doing a good job yesterday, that came right from Upton's AFD yesterday.

:banned:

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Very impressive hourly rainfall amounts under those back-building cells.

yeah if we get into it here out in Jersey we could definitly see a repeat if not worse than yesterday. I heard the traffic was horrible yesterday around Rt. 46 & 3 due to flooding. I saw some minor street flooding on Rt. 23 also with one lane partially blocked near High Crest Road.

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yeah if we get into it here out in Jersey we could definitly see a repeat if not worse than yesterday. I heard the traffic was horrible yesterday around Rt. 46 & 3 due to flooding. I saw some minor street flooding on Rt. 23 also with one lane partially blocked near High Crest Road.

If the storms train right over your area you will pick up a lot of rain in a short period of time.

There's no shortage of heavy rain/flooding closed low analogs.

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NEAR TERM /THROUGH TONIGHT/...

1220 PM UPDATE...A SEVERE THUNDERSTORM WATCH WAS ISSUED BY THE SPC

FOR AREAS W OF THE HUDSON RIVER INCLUDING NORTHEAST NJ AND ORANGE

AND ROCKLAND COUNTIES UNTIL 8 PM THIS EVENING.

BASED ON CURRENT OBSERVATIONS AND NEAR TERM FORECAST TRENDS...THE

HIGHEST THREAT IS MODERATE FOR BOTH LARGE HAIL AND DAMAGING WINDS.

IN ADDITION...NARROW BANDS OF HEAVY SHOWERS AND TSTMS WILL PRODUCE

TORRENTIAL RAINFALL WITH RATES OF 1 INCH PLUS PER HOUR. THIS MAY

LEAD TO ADDITIONAL URBAN AND SMALL STREAM FLOODING ACROSS THE

REGION AS SMALL STREAMS SLOWLY RECEDE ACROSS NORTHEAST NJ AND THE

LOWER HUDSON VALLEY.

STAY TUNED FOR POSSIBLE WARNINGS AND ADVISORIES.

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I don't think the storms make it as far east as the watch extends. I would expect they remain back west where the best dynamics and lift are. Don't think things shift east until it is to late for some area. Just had a nice cell move through here in Newark, DE. Nice louds claps of thunder and some torrential rains, but that is all.

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latest infrared images show considerable cooling of the cloud tops over NJ

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

Primarily high clouds, cirrus wrapping around the flow and being further saturated from above, not below or near the surface. What you see is streaming clouds associated with the jet, there is nothing building up underneath them, convectively, so to speak. In fact, the high clouds are precluding destabilization/surface instability by putting a lid on the heating. Not to say that thunderstorms won't progress or initiate over NJ/NYC, but those cooling cloud tops are not indicative of any threat. I think most of the precip will stay confined where surface based instability is being realized over eastern PA, and later into extreme western/southern NJ.

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when I see a broad area of around 0.75" on the GFS I bump it up just a hair to account for the lower resolution. Not really sure why it matters though, its generally a terrible model to use for short term QPF. Sure there are days that it does a good job and then you get days like yesterday where none of the models did a very good job on picking it up. And before a smart one on here says that I'm wrong about none of the models doing a good job yesterday, that came right from Upton's AFD yesterday.

Its not a broad area of .75" though. Its .50"-.75". And checking soundings, MMU is .57", so its closer to .50" then .75"

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Its not a broad area of .75" though. Its .50"-.75". And checking soundings, MMU is .57", so its closer to .50" then .75"

A higher res version like the one for the NAM on E-WALL would have probably yielded pockets of heavier QPF. The GFS fields in my opinion are way too smooth for this type of convective activity.

Those storms over SE PA have barely moved. Estimated dopplar radar total accumulations in a few spots are exceeding 3" with one bullseye of 5"+. So while the very heavy rain will fall in isolated areas, those that do get it will get quite alot.

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