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12/29 Winter Storm OBS/Disco Part II


earthlight

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I did some comparisons from what the 00z NAM soundings showed for my area (by Long Branch) at 1AM. The NAM showed .7C (or 33.2 Fahrenheit) at the surface. I was at 28.4 degrees at the time (or -2C) . This is almost a 3C difference, and 6 degree fahrenheit distance (do the math!) Point being is the NAM soundings are clearly too warm, at least at the surface. It is now 330AM, and my temperature is 30.3 , a 2 degree increase from the cloud cover (as expected).

I did GFS soundings earlier, and was too warm at surface as well, although not as pronounced as the NAM.

Point being lets not hug the models - low level warmth especially. The model does not take into effect the dynamic cooling which will occur when the precipitation is falling AND the warm surface temps are overdone, at least so far , and usually are. If precipitation is falling at a decent pace - I suspect most areas will be snow for the duration of the event (in the NYC/N NJ/ C NJ area). Any mixing or rain would most likely occur a little bit after the precipitation starts, and the areas highest at risk would obviously be coastal areas - although I'm not convinced it'll mix if precipitation starts falling hard early. If precipitation lightens up, don't be surprised to see the temp jump a degree or 2, and it to be "drizzling" .

Not sure we will see the amount 6z NAM depicts - NAM tends to overdo qpf amounts, but we shall see.

I'd say many people will see 2-4" from this event - with some areas higher especially those closer to the coast in general - but any mixing that would occur early on may hinder those totals obviously.

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New TAFs tell us where Upton is headed with this....they seem to think a hit on the backside as the low deepens but a mix initially....

KLGA 290830Z 2908/3006 VRB04KT P6SM FEW040 BKN100 BKN200

TEMPO 2913/2915 2SM -SN BR BKN012

FM291500 07006KT 2SM -SNRA BR BKN007 OVC015

FM291900 02012KT 1SM RASN BR BKN004 OVC012

FM292300 34014G22KT 1SM -SN BR OVC009

FM300500 32017G27KT P6SM OVC015

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Advisory continues for the 5 boros on west.

--

400 AM EST SAT DEC 29 2012

...WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM 8 AM THIS

MORNING TO 6 AM EST SUNDAY...

* LOCATIONS...THE LOWER HUDSON VALLEY OF NEW YORK...SOUTHERN

CONNECTICUT AND NORTHEAST NEW JERSEY.

* HAZARD TYPES...SNOW.

* ACCUMULATIONS...SNOW ACCUMULATION OF 3 TO 5 INCHES. A FEW SPOTS

MAY EXCEED 6 INCHES...ESPECIALLY OVER INTERIOR CONNECTICUT AND

THE HUDSON RIVER VALLEY.

* TEMPERATURES...IN THE UPPER 20S TO AROUND 30.

* VISIBILITIES...ONE QUARTER TO ONE HALF MILE AT TIMES.

* TIMING...THE SNOW WILL BEGIN THIS MORNING AND CONTINUE THROUGH

THIS EVENING...TAPERING OFF OVERNIGHT.

* IMPACTS...MODERATE SNOW WILL MAKE FOR DANGEROUS TRAVEL DURING

THE AFTERNOON AND INTO THE NIGHT.

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A few of us talked about this earlier, but the NAM closes off the mid level centers two or three hours earlier than it was previously. The best lift shifts to the NW side of the surface low which is slightly more tucked in off the coast. As a result the CCB develops basically overhead and you can see it here with this banding signal over NE NJ and NYC.

http://www.meteo.psu.edu/~fxg1/NAMSFC4_6z/rad16.gif

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A few of us talked about this earlier, but the NAM closes off the mid level centers two or three hours earlier than it was previously. The best lift shifts to the NW side of the surface low which is slightly more tucked in off the coast. As a result the CCB develops basically overhead and you can see it here with this banding signal over NE NJ and NYC.

http://www.meteo.psu...C4_6z/rad16.gif

Gee what a surprise.. NENJ in for another pounding.. How many times can a deform band form over u guys?

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Can't wait to see the freakout when there's a bit of shadowing between the initial lift over PA/NY and the coastal...should make it look like a nice screw zone setting up over NYC and I'm sure it will take less than 30 minutes for Noreaster27 and others to come in screaming about a bust. Save this post for tomorrow morning around 9am. You can see it here on the NAM

http://www.meteo.psu.edu/~fxg1/ETAFLOAT_6z/f12.gif

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Can't wait to see the freakout when there's a bit of shadowing between the initial lift over PA/NY and the coastal...should make it look like a nice screw zone setting up over NYC and I'm sure it will take less than 30 minutes for Noreaster27 and others to come in screaming about a bust. Save this post for tomorrow morning around 9am. You can see it here on the NAM

http://www.meteo.psu...LOAT_6z/f12.gif

The current forecast could bust tremendously. It appears to me that most of the area is going to miss the initial area of snow. I'm surprised to see the NWS forecasting any snow really before 12-1pm. I could see the far NW areas like Sussex or Orange seeing some snow from the first round but most of the area little else. Very possible if the band of snow associated with the surface low is a bit east of the RAP/NAM that places like TEB/EWR/NYC could see only 1-2 inches while LI sees 3-5 inches.

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Can't wait to see the freakout when there's a bit of shadowing between the initial lift over PA/NY and the coastal...should make it look like a nice screw zone setting up over NYC and I'm sure it will take less than 30 minutes for Noreaster27 and others to come in screaming about a bust. Save this post for tomorrow morning around 9am. You can see it here on the NAM

http://www.meteo.psu...LOAT_6z/f12.gif

hahahah yeah. Here's the next frame. We will be ripping under this

f15.gif

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Can't wait to see the freakout when there's a bit of shadowing between the initial lift over PA/NY and the coastal...should make it look like a nice screw zone setting up over NYC and I'm sure it will take less than 30 minutes for Noreaster27 and others to come in screaming about a bust. Save this post for tomorrow morning around 9am. You can see it here on the NAM

http://www.meteo.psu.edu/~fxg1/ETAFLOAT_6z/f12.gif

And since the coastal is stronger and develops earlier via the mid level centers closing off, the primary gets robbed, which further enhances the shadowing.

Also, if the trends for the coastal to close off its mid level center sooner remain true, that would greatly help the wind component in the BL for coastal regions, and any rain would turn over to snow quicker.

I'm still wary for LI, but I have my hopes. Tomorrow will be a great day to test nowcasting skills.

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The current forecast could bust tremendously. It appears to me that most of the area is going to miss the initial area of snow. I'm surprised to see the NWS forecasting any snow really before 12-1pm. I could see the far NW areas like Sussex or Orange seeing some snow from the first round but most of the area little else. Very possible if the band of snow associated with the surface low is a bit east of the RAP/NAM that places like TEB/EWR/NYC could see only 1-2 inches while LI sees 3-5 inches.

My forecast for LI is anywhere from 0-12". And I'm not totally kidding :P so much bust potential either way, based on the timing of the mid level centers closing off and where exactly the CCB sets up.

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