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NYC/PHL Potential Jan 11-14 Event Discussion Part Two


NickD2011

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it's my impression the general weenie gives more credence to the off-hour runs than actual mets... but i certainly could be wrong.

I use them all equally. It was probably true 10 years ago when data assimilation techniques weren't nearly as advanced as they are now. Models have changed.

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I use them all equally. It was probably true 10 years ago when data assimilation techniques weren't nearly as advanced as they are now. Models have changed.

The only one run of one model that I really have no use for is the 18Z NAM. For some reason, if one model is going to have a wacky run, it's that one.

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It seems the GFS still wants to track this storm east of the ECM in general...I wouldn't be surprised if it tucks in closer to the coast as the Euro shows (and what the 12z NAM displayed) and gets NYC with heavier CCB banding, but at least we're virtually assured of a 6" snowfall at that point with the potential for significantly more.

Snowman.gif

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE NEW YORK NY

427 PM EST SUN JAN 9 2011

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...

-- Changed Discussion --STRONG SUBSIDENCE CONTINUES INTO MON...SO A MOSTLY SUNNY DAY

EXPECTED WITH ONLY FEW-SCT STRATOCU ATOP THE INVERSION...AND

MIXING BELOW RESULTING IN ONE MORE DAY OF GUSTY NW WINDS.

HIGH PRESSURE WILL NOSE DOWN FROM ONTARIO MON NIGHT.

UNDERCUT COLDEST MOS GUIDANCE FOR LOWS...BUT NOT QUITE AS MUCH AS

I NORMALLY WOULD FOR SNOW COVERED AREAS...SINCE A 15-20 KT

NORTHERLY FLOW JUST OFF THE DECK SHOULD PROVIDE ENOUGH MECHANICAL

TURBULENCE TO LIMIT RADIATIONAL COOLING. SOME HIGH CLOUDS MAY MOVE

IN LATE.

FOCUS THEN TURNS TO WHAT WILL LIKELY BE ANOTHER MAJOR

SNOWSTORM...THE SECOND FOR MUCH OF THE AREA IN JUST A LITTLE OVER

TWO WEEKS AND THE THIRD FOR MUCH OF SOUTHERN CT! SIDED WITH A 12Z

NAM/ECMWF BLEND FOR THE NASCENT LOW PRESSURE SYSTEM EXTENDING FROM

THE SRN PLAINS AND LOWER MISSISSIPPI VALLEY INTO THE NORTHERN GULF

OF MEXICO. SAT WV IMAGERY ALREADY SHOWS A WELL DEVELOPED

BAROCLINIC LEAF AND COMMA HEAD...WITH SNOWFALL RATES OF 1-2

INCHES/HOUR ALREADY TAKING PLACE IN THE ARKLATEX REGION...AND A

SUBTROPICAL MOISTURE PLUME ORIGINATING FROM NEAR A TROPICAL

DISTURBANCE S OF MEXICO...AND ABOVE MENTIONED MODEL GUIDANCE HAS

PICKED UP ON THIS. PROLIFIC LIGHTNING OVER THE N CENTRAL GULF OF

MEXICO MAY BE INDICATIVE OF STRONGER SHORTWAVE RIDGING AHEAD OF

THE SYSTEM THAN MOST MODEL FORECASTS...WHICH MAY FORCE AN EVENTUAL

FARTHER W LOW TRACK...AND THE NAM SEEMS TO BE PICKING UP ON

THIS. EVEN SO...STRONG ISALLOBARIC N-NE LOW LEVEL FLOW INDUCED BY

RAPID PRESSURE FALLS AS THE DEVELOPING SFC LOW MOVES FROM NE OF

HATTERAS TO SOMEWHERE BETWEEN MONTAUK AND 40N/70W TUE NIGHT BY 12Z

WED SHOULD KEEP PRECIP ALL SNOW OVER NEARLY THE ENTIRE CWA...WITH

ONLY THE FORKS OF LONG ISLAND STILL IN QUESTION. WEAKER/LESS WET

GFS SFC SOLUTION ALLOWS FOR LESS OF AN ISALLOBARIC LOW LEVEL WIND

COMPONENT AND THEREFORE MORE ONSHORE AND BLYR WARMING...WITH MIXED

PRECIP TUE NIGHT ALL THE WAY BACK TO COASTAL CT AND ALL RAIN FOR

MOST OF THE NIGHT OVER LONG ISLAND. THIS SOLUTION HAS BEEN

REJECTED ESPECIALLY SINCE THE GFS WAS ALSO TOO WARM IN COASTAL

SECTIONS FOR THE LATE DECEMBER BLIZZARD.

WINDS COULD ALSO BE AN ISSUE IN NYC AND COASTAL SECTIONS DURING

THE HEIGHT OF THE STORM LATE TUE NIGHT INTO WED MORNING...WITH

GUSTS OVER 35 MPH POSSIBLE. THESE WINDS WILL LIKELY PRODUCE

BLOWING/DRIFTING OF SNOW...BUT IT IS TOO EARLY TO SAY WHETHER THEY

WILL COINCIDE WITH HEAVY SNOW FOR A LONG ENOUGH PERIOD TO PRODUCE

TRUE BLIZZARD CONDITIONS AS WITH THE LATE DECEMBER STORM.

THAT SAID...CONFIDENCE IN SIGNIFICANT SNOWFALL AMOUNTS OVER 6

INCHES IS RUNNING HIGH...WITH LIKELIHOOD OF MUCH GREATER TOTALS

WHERE MESOSCALE BANDING SETS UP...MUCH TOO EARLY TO PINPOINT WHERE

THIS WILL OCCUR. HWO WILL CONTINUE TO ADVERTISE THIS POTENTIAL...

AND IT IS POSSIBLE THAT WATCHES COULD BE RAISED OVERNIGHT.

AS THE UPPER LOW ASSOCIATED WITH THE STORM PASSES E OF THE AREA BY

MIDDAY WED...TROUGHING LAGGING BEHIND COULD ALLOW LIGHT SNOW TO

PERSIST INTO WED AFTERNOON...WHILE A BLUSTERY NW WIND CONTINUES.-- End Changed Discussion --

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It seems the GFS still wants to track this storm east of the ECM in general...I wouldn't be surprised if it tucks in closer to the coast as the Euro shows (and what the 12z NAM displayed) and gets NYC with heavier CCB banding, but at least we're virtually assured of a 6" snowfall at that point with the potential for significantly more.

i feel like with today's models coming in, there is sort of a consensus (maybe aside from the 12z NAM) that we are looking at a moderate snowstorm, maybe 4-6 in PHL, 8-10 in NYC......those might even be a little on the high end. Out of all the storms recently, this, to me at least, seems to have more model agreement as we get within 48 horus or so.

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It seems the GFS still wants to track this storm east of the ECM in general...I wouldn't be surprised if it tucks in closer to the coast as the Euro shows (and what the 12z NAM displayed) and gets NYC with heavier CCB banding, but at least we're virtually assured of a 6" snowfall at that point with the potential for significantly more.

Snowman.gif

It seems that even though the GFS is stronger this run with the sfc low, the S/W energy is faster and the low books it out of here. The 700mb low also doesn't close until it's pretty much out of here, so SNE gets in on the heavier banding that gets them to 1"+, but we get mostly heavier overrunning snow as the coastal bombs. Our storm is maybe 12 hours long tops on this run. The Euro also sped the storm up but the fast deepening made up for it. It's the difference IMO between a 5-10 and maybe 10-15" event for most of the area. Still a high end moderate to major event but nothing huge if it keeps speeding up.

It's not a huge concern of me right now, but hopefully the fast/progressive trend stops because we need the storm to be slow enough to allow the energy to catch up to it and cause the CCB to form in time. Right now it's a very close call.

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GFS EnSembles show .75-1 QPF for City(read on another board) and 50.75 back Further West into NJ.. Not bad Still think we haven't seen the Max QPF run(Judging by the Moisture Plume down South) with this storm which could happen tonight or Tomorrow morning.

that is the big player as of now for the big snows. the gfs i dont think is taking the huge moisture plume right now heading into the southern stream. the european i believe has the right idea and has amped up its qpf. the 0z runs of the gfs and the euro are going to be crucial tonight in taking in the additional moisture into the forecast

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Will the NYC/LI/Jersey shore areas have mixing issues with this scenario?

thats all going to depend on how quick the coastal low bombs out and crashes the rain/snow line offshore the weaker the storm the more likely mixing or changeover to rain in the coastal areas. upton has discounted the gfs weak solution that depicted that solution.

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that is the big player as of now for the big snows. the gfs i dont think is taking the huge moisture plume right now heading into the southern stream. the european i believe has the right idea and has amped up its qpf. the 0z runs of the gfs and the euro are going to be crucial tonight in taking in the additional moisture into the forecast

Where do these ideas come from? The 12z GFS actually has more moisture in the low levels tomorrow morning than the European does. The European dumps more QPF simply because it has a stronger low and more forcing for vertical ascent. That's it. The stronger the surface low gets (and associated northern stream dynamics aloft), the more QPF there will be.

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thats all going to depend on how quick the coastal low bombs out and crashes the rain/snow line offshore the weaker the storm the more likely mixing or changeover to rain in the coastal areas. upton has discounted the gfs weak solution that depicted that solution.

The weaker solutions are going to be colder, though, like the GFS; anytime the low is further east, it's going to keep the mix line offshore.

You can see that JFK is clearly all snow at 60 hours on the 18z GFS, and they're one of the warmest locations in this storm:

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Hopefully Upton is correct, and not the gfs.

the european has been the more consistent model here while the gfs has been inconsistent and too warm. upton i think is making the right call with the european currently, liable to change though, personally i think the qpf is going to increase signifigantly from here with the models with the introduction of gulf/stj moisture and it being incorporated into the next model runs

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Where do these ideas come from? The 12z GFS actually has more moisture in the low levels tomorrow morning than the European does. The European dumps more QPF simply because it has a stronger low and more forcing for vertical ascent. That's it. The stronger the surface low gets, the more QPF there will be.

im just trying to understand the storm, thanks for the correction though appreciate it am19psu.

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Where do these ideas come from? The 12z GFS actually has more moisture in the low levels tomorrow morning than the European does. The European dumps more QPF simply because it has a stronger low and more forcing for vertical ascent. That's it. The stronger the surface low gets (and associated northern stream dynamics aloft), the more QPF there will be.

AHH, not exactly so...what about when the low becomes vertically stacked??

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