NYC CWA Feb 1-2 Storm Discussion

[jconsor]

No, they have 2-5" for the Bronx, too. In fact, the text of the Winter Storm Watch for the Bronx appears to be exactly the same as for other parts of NYC.

* LOCATIONS...THE BRONX.

* HAZARDS...SNOW AND SLEET TUESDAY. SNOW...SLEET AND FREEZING

RAIN TUESDAY NIGHT. FREEZING RAIN TO RAIN WEDNESDAY.

* ACCUMULATIONS...2 TO 5 INCHES OF SNOW ACCUMULATION...AND A

QUARTER TO PERHAPS A HALF INCH OF ICE ACCUMULATION BY LATE

WEDNESDAY.

So they have Manhattan for 2-5" and 5-9" for the Bronx. Well, the Bronx is on the mainland and Manhattan and the other boros arent Manhattan and Staten Island are on their own islands and Brooklyn and Queens are part of Long Island.

[simpsonsbuff]

No, they have 2-5" for the Bronx, too. In fact, the text of the Winter Storm Watch for the Bronx appears to be exactly the same as for other parts of NYC.

* LOCATIONS...THE BRONX.

* HAZARDS...SNOW AND SLEET TUESDAY. SNOW...SLEET AND FREEZING

RAIN TUESDAY NIGHT. FREEZING RAIN TO RAIN WEDNESDAY.

* ACCUMULATIONS...2 TO 5 INCHES OF SNOW ACCUMULATION...AND A

QUARTER TO PERHAPS A HALF INCH OF ICE ACCUMULATION BY LATE

WEDNESDAY.

It could be they are setting themselves for a shift down the line...

[Hailstorm]

Per these maps, only 3 tenths of an inch of pure liquid rainfall falls in NYC! Thus, the snow pack will mostly be intact after the event!

[jconsor]

That map is showing the amount of ice that accrues on the ground and other exposed surfaces, not the liquid equivalent that falls as freezing rain.

However, I agree that little rain will fall at Central Park - perhaps just the last 3-4 hours of the significant precip. on Wed afternoon, if at all. JFK and southern Queens/Brooklyn are a different story.

Per these maps, only 3 tenths of an inch of pure liquid rainfall falls in NYC! Thus, the snow pack will mostly be intact after the event!

[tmagan]

06Z RGEM Total Freezing Rain through hour 54

[Hailstorm]

That map is showing the amount of ice that accrues on the ground and other exposed surfaces, not the liquid equivalent that falls as freezing rain.

However, I agree that little rain will fall at Central Park - perhaps just the last 3-4 hours of the significant precip. on Wed afternoon, if at all. JFK and southern Queens/Brooklyn are a different story.

I think there is a misunderstanding. I meant to say that according to the snow map, 4.2" is depicted in NYC which equates to 0.4" of liquid water. Combine that with 0.31" of ice accrual from the ice map and you end up with about 0.71" of frozen precipitation. Then, you take a look at the liquid map which tells you that a total of 1.05" has fallen throughout the event, counting the frozen and freezing precipitation types also. Thus, 1.05" minus 0.71" equals only about 0.34" falling as plain rain. I hope that clears it up.

[simpsonsbuff]

06Z RGEM Total Freezing Rain through hour 54

Where do u get those maps? I gotta bookmark it .

[tmagan]

06Z RGEM Three hour Dominant Precip. at hour 54

[jconsor]

0.31" of ice accrual does not mean 0.31" of QPF falls as ice, it means 0.31" of ice accrues on exposed surfaces.

I think there is a misunderstanding. I meant to say that according to the snow map, 4.2" is depicted in NYC which equates to 0.4" of liquid water. Combine that with 0.31" of ice accrual from the ice map and you end up with about 0.71" of frozen precipitation. Then, you take a look at the liquid map which tells you that a total of 1.05" has fallen throughout the event, counting the frozen and freezing precipitation types also. Thus, 1.05" minus 0.71" equals only about 0.34" falling as plain rain. I hope that clears it up.

[tmagan]

Where do u get those maps? I gotta bookmark it .

1) Go to http://meteocentre.com/home_e.html

2) Scroll down to: Vizaweb: web access to CMC products.

[A-L-E-X]

No, they have 2-5" for the Bronx, too. In fact, the text of the Winter Storm Watch for the Bronx appears to be exactly the same as for other parts of NYC.

* LOCATIONS...THE BRONX.

* HAZARDS...SNOW AND SLEET TUESDAY. SNOW...SLEET AND FREEZING

RAIN TUESDAY NIGHT. FREEZING RAIN TO RAIN WEDNESDAY.

* ACCUMULATIONS...2 TO 5 INCHES OF SNOW ACCUMULATION...AND A

QUARTER TO PERHAPS A HALF INCH OF ICE ACCUMULATION BY LATE

WEDNESDAY.

Ah ok-- when he said they have the Bronx listed by itself, I thought he meant they had diff accum for them. Personally, I like the graphics much more as they give much more info than a text based forecast ever could.

[Snowlover11]

oh boy, 5-9" of snow and upwards of an half inch of ice

[A-L-E-X]

That map is showing the amount of ice that accrues on the ground and other exposed surfaces, not the liquid equivalent that falls as freezing rain.

However, I agree that little rain will fall at Central Park - perhaps just the last 3-4 hours of the significant precip. on Wed afternoon, if at all. JFK and southern Queens/Brooklyn are a different story.

Is the airmass going to be about as cold as Jan 1994 or VD 2007 was? Both of those times, JFK stayed below freezing, while areas east of Oceanside got above freezing. The 0C line was oriented SW / NE

I remember seeing some PWS from VD 2007 (Jan 1994 was too early for wunderground PWS data) and it was interesting how JFK had a high around 30, while it was in the upper 30s and lower 40s east of here around Freeport and to our south in Long Beach.

[tmagan]

06Z RGEM Total Snow through hour 54.

[tmagan]

06Z RGEM Total Rain through hour 54.

[Hailstorm]

0.31" of ice accrual does not mean 0.31" of QPF falls as ice, it means 0.31" of ice accrues on exposed surfaces.

Oh, I see now. Thanks.

By the way, you did a great job with analyzing the tropical season last year in the old Eastern WX forums. I loved reading your insightful posts about the memorable hurricanes last year. I hope you will do the same this year. I have a feeling a cyclone will impact the NYC area sooner or later because we are still in a La Nina. It was a real close call with Hurricane Earl last year.

[tmagan]

06Z RGEM one hour dominant precip. at hour 54.

[tmagan]

If you assume a 12Z Wednesday transition to rain for NYC and Long Island, there is still, with clogged storm drains, a very significant flooding threat for those aforementioned areas.

[tmagan]

06Z RGEM hour 54 mslp superimposed with the change in pressure with respect to time over a three hour period.

[jconsor]

The air mass is expected to be at least 5F warmer than Jan 1994 and about as cold as VD 2007, but not as dry (dew points only around 10F instead of around -5 to -10F prior to VD 2007). I would expect the surface isotherms to be oriented WSW-ENE in this case, but perhaps curving more SW-NE over Suffolk County where there will likely be a coastal front.

Thus Oceanside should be only about 1-2F warmer than JFK, but ISP has a good chance of getting much warmer than JFK.

Is the airmass going to be about as cold as Jan 1994 or VD 2007 was? Both of those times, JFK stayed below freezing, while areas east of Oceanside got above freezing. The 0C line was oriented SW / NE

I remember seeing some PWS from VD 2007 (Jan 1994 was too early for wunderground PWS data) and it was interesting how JFK had a high around 30, while it was in the upper 30s and lower 40s east of here around Freeport and to our south in Long Beach.

[A-L-E-X]

If you assume a 12Z Wednesday transition to rain for NYC and Long Island, there is still, with clogged storm drains, a very significant flooding threat for those aforementioned areas.

It's hilarious to see Upton forecasting 9" of snow for the southern CT coast, while 4" for the north shore of Long Island. BOX's numbers are way different.

[SnowGoose69]

06z GFS 3C cooler at 850mb at hour 54 than the 00z run at hour 60...it seems the off hour runs in these events often come in colder for some reason.

[tmagan]

Looking at the dp/dt map at hour 54, it seems to indicate a secondary redevelopment along the Jersey shore.

[A-L-E-X]

0.31" of ice accrual does not mean 0.31" of QPF falls as ice, it means 0.31" of ice accrues on exposed surfaces.

How do they determine how much will accrue? It has to be an estimate, because different surfaces accrue at different rates. It would be so much easier just to say-- this is the amount of liquid precip that falls with the surface temp under 0 C.

[A-L-E-X]

The air mass is expected to be at least 5F warmer than Jan 1994 and about as cold as VD 2007, but not as dry (dew points only around 10F instead of near 0F prior to VD 2007). I would expect the isotherms to be oriented WSW-ENE in this case, but perhaps curving more SW-NE over Suffolk County where there will likely be a coastal front.

Thus Oceanside should be only about 1-2F warmer than JFK, but ISP has a good chance of getting much warmer than JFK.

Thanks-- I love these little details for some reason. Each storm seems to have its own "personality" and its intriguing seeing where these microfronts set up.

[tmagan]

It's hilarious to see Upton forecasting 9" of snow for the southern CT coast, while 4" for the north shore of Long Island. BOX's numbers are way different.

In my opinion, the flooding threat is not being emphasized enough.

[A-L-E-X]

06z GFS 3C cooler at 850mb at hour 54 than the 00z run at hour 60...it seems the off hour runs in these events often come in colder for some reason.

Im wondering the reasons for this too. The NCEP guys seem insistent there's no difference between the runs and the verification scores are the same, but the 6z and especially the 18z runs seem always be out on their own. If theyre all ingesting new data, I wonder what the reasons for this might be?

[A-L-E-X]

If you assume a 12Z Wednesday transition to rain for NYC and Long Island, there is still, with clogged storm drains, a very significant flooding threat for those aforementioned areas.

Im wondering if we all warm up quicker than expected and end up in the lower 40s for a time.

[A-L-E-X]

Whats the GFS showing for the weekend storm? Still OTS?

[tmagan]

Im wondering if we all warm up quicker than expected and end up in the lower 40s for a time.

I think the models are running a little too cold for this event, but the 06Z UKMET bisects L.I. and NYC with the 0^oC isotherm for the entire day on Wednesday. Fun to forecast, I'll have to say that.