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NYC Area February 1st-2nd OBS and Discussion


earthlight

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Latest surface analysis shows a 1032 mb high still firmly parked just north of the NY/VT border. A 997 mb low is located over southern Illinois about to cross over into southern Indiana. The pressure was steady over the past two hours over much of the area but pressure falls were beginning to advance eastward. Our weak low from this morning was now located well SE of Cape Cod. Precip is beginning to break out in earnest just to the west of the CWA with temps well below freezing in most spots.

Nice summary/map--appreciate the contribution.

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As is always the case at this time frame, its now nowcasting time. I can see using the NAM since its a short range model to begin with but the GFS for all intents and purposes is about as usefull as an umbrella in a hurricane in this time frame.

NAM is actually pretty close in terms of placement of HP up north and SLP out in IL. The HP was progged perfectly by the NAM and the SLP was 2mb too high (NAM had it at 1000mb). Upper air maps are also fairly close. 850mb freezing line running across Northern PA and still up by southern Sullivan Co in NY at this time as depicted perfectly by the NAM. If anything, it just has the surface temps a degree or 2 high.

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again, very ROUGH approximations, comparing 18z 9hr NAM 2m temp forecast to actual 3z obs...

looks pretty much on track, although maybe a tick milder than forecast south, a tick cooler up north.

post-533-0-13345800-1296617746.jpg

now that is an insane temperature line on long island...now if you correlate the 26 line to the topographic maps of the island posted earlier, it seems that the areas with the highest elevation are all below 26...from those areas to just north of the south shore...any idea why that pattern other than elevation?

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NAM is actually pretty close in terms of placement of HP up north and SLP out in IL. The HP was progged perfectly by the NAM and the SLP was 2mb too high (NAM had it at 1000mb). Upper air maps are also fairly close. 850mb freezing line running across Northern PA and still up by southern Sullivan Co in NY at this time as depicted perfectly by the NAM. If anything, it just has the surface temps a degree or 2 high.

As I said, the NAM can be usefull but the GFS....not so much. The GFS is a very good medium range model.

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I was just basing that off of surface obs further to our west.

current synoptic setup is as clear and perfect of a CAD signiauture as I've seen in quite some time. Most guidance is now even keeping most if not all the area below freezing through 12z WED. Even if temps rise a degree or two it won't matter over the ISW areas.

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As of 10:25PM from Upton

SHORT TERM /1 AM WEDNESDAY MORNING THROUGH THURSDAY/...

-- Changed Discussion --HIGHLY COMPLEX SYSTEM TO IMPACT THE REGION OVERNIGHT THROUGH WED... WITH

SIGNIFICANT ICE ACCUMULATIONS FOR THE INTERIOR...AND FREEZING RAIN

CHANGING TO PLAIN RAIN AND POSSIBLY BECOMING HEAVY AT TIMES FOR

COASTAL AREAS.

LOW PRES OVER THE LOWER MISSISSIPPI VALLEY WILL TRACK NE INTO THE

TN AND OH VALLEYS BY MIDNIGHT...THEN MOVES INTO WESTERN NY BY WED

MORNING. MEANWHILE...A SECONDARY LOW WILL FORM SOMEWHERE OVER THE

DELMARVA LATE TONIGHT AND MAKE A RUN AT NYC WED MORNING THROUGH

EARLY AFTERNOON. THERE STILL IS SOME UNCERTAINTY AS TO THE TRACK

AND POSITIONING OF THE LOW...WHERE THE GFS IS THE SLOWER OF THE

MODELS...AND THERE APPEARS TO BE A GOOD CLUSTERING AMONG THE

OPERATIONAL GFS...THE GEFS AND EVEN THE ECMWF...WHILE THE NAM

SEEMS TO HAVE A SLIGHTLY FASTER TRACK AMONG THE MODELS.

SFC TEMPS WILL BE SLOW TO WARM LATE TONIGHT...AND AS PRECIP MOVES

INTO THE REGION...WILL GENERALLY EXPECT FREEZING RAIN WITH SOME

SLEET POSSIBLE. H8 TEMPS WILL WARM TO 0-2C ACROSS THE INTERIOR AND

TO 2-4C FOR THE SOUTH. WITH SFC TEMPS IN THE INTERIOR NOT WARMING

MUCH ABOVE THE UPPER 20S...THIS SETS UP FOR A PROLONGED FREEZING

RAIN EVENT. ICE STORM WARNING REMAINS UP FOR THESE AREAS...AS UP

TO 1/2" ICE ACCUMULATION IS EXPECTED. FOR THE REST OF THE AREA...

GENERALLY INCLUDING LONG ISLAND...NYC...COASTAL PORTIONS OF NE NJ

AND SOUTHERN AND EASTERN CT...ICE ACCUMULATIONS OF UP TO 1/4" ARE

EXPECTED BEFORE WINDS SHIFT TO THE EAST...AND ALLOW SFC TEMPS TO

WARM INTO THE MID AND UPPER 30S...POSSIBLY APPROACHING 40 IN SOME

SPOTS ON LONG ISLAND. SLEET AND FREEZING RAIN LOOK TO CHANGE TO

PLAIN RAIN WED MORNING ACROSS NYC/COASTAL NJ/LONG ISLAND AROUND

9AM...AND THEN AROUND NOON FOR SOUTHERN AND EASTERN CT. WITH SUCH

WARM AIR ALOFT...NOT EXPECTING SNOW DURING THE DAY...SO WILL

REMOVE FROM FCST. WITH PWATS APPROACHING 1 INCH IN THE

REGION...COULD EVEN EXPERIENCE SOME HEAVY RAIN AT TIMES DURING THE

DAY WED.

FOR INTERIOR PORTIONS OF NE NJ...THE LOWER HUDSON VALLEY AND

INTERIOR PORTIONS OF NW CT...TEMPS DO NOT LOOK TO RISE ABOVE

FREEZING AT ALL ON WED. SO ALL PRECIP THAT FALLS WILL BE FREEZING

RAIN ALONG WITH SOME SLEET AND NO PLAIN RAIN EXPECTED. THIS WILL

RESULT IN SIGNIFICANT ICE ACCUMULATIONS ON ROADS...WALKWAYS...

TREES AND POWER LINES. THIS IS A DANGEROUS SITUATION. NUMEROUS

TREES AND POWER LINES CAN BE EXPECTED TO FALL...RESULTING IN POWER

OUTAGES. EVEN AREAS UNDER THE ADVISORY AND NOT THE ICE STORM

WARNING SHOULD TAKE PRECAUTIONS...AS 1/4" OF ICE WILL MAKE TRAVEL

TREACHEROUS AND COULD ALSO RESULT IN DOWNED TREES AND POWER LINES.

PRECIP TAPERS OFF BY WED EVENING FROM WEST TO EAST...LIKELY AS

SNOW ACROSS THE INTERIOR AND A RAIN/SNOW MIX AT THE COAST.

WITH STRONG NW WINDS BEHIND THIS INTENSE SYSTEM...BITTERLY COLD

AIR WILL FUNNEL INTO THE LOCAL AREA WED NIGHT. TEMPS WILL DROP

FAIRLY RAPIDLY INTO THE 20S...POSSIBLY RESULTING IN A RAPID FREEZE

OF ANY LIQUID ON UNTREATED AND POSSIBLY EVEN TREATED SURFACES.

TRAVEL WED NIGHT COULD BECOME QUITE DANGEROUS.

CANADIAN HIGH PRESSURE AND WEAK RIDGING ALOFT BUILDS IN THURSDAY

WITH DRY AND COLD CONDITIONS EXPECTED.-- End Changed Discussion --

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Where do you get your temp from? I'm checking wunderground stations from central Brooklyn and they are at 28 degrees.

Very impressive as the ice area is expanding as we speak, as well as being fed by an influx of moisture coming in off the Gulf.

post-455-0-93997500-1296618647.gif

Temps in Southern Brooklyn has dropped 1 degree to 26* F from 27* F in the past 20 minutes with a NE wind still. Barometer remains unchanged for the past 2 hours @ 30.18".

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current synoptic setup is as clear and perfect of a CAD signiauture as I've seen in quite some time. Most guidance is now even keeping most if not all the area below freezing through 12z WED. Even if temps rise a degree or two it won't matter over the ISW areas.

not sure how accurate it is, but ewall surface maps show high pressure actually nosing further south over the last 2-3 hours across NYC metro and LI. that might partially explain why some temps across interior western LI have fallen into the mid-20s.

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