December 9th-10th Forecast Map(s) Cut-Off Coastal Storm

A large storm system expected to bring rain, snow, and wind is eyeing the Northeast region this upcoming Tuesday through Thursday. Most of the action is expected to occur on Tuesday, however, since we are dealing with a cut-off storm lingering effects will last into Thursday. A 1040 mb High Pressure system is stationed over eastern Canada which will prevent this storm from scurrying out to sea. Instead, as the northern stream energy digs into the base of the trough, H5 is going to close off and the storm will cut-off from the jet stream. Once it does so, the surface low is expected to occlude (slow down and potentially stall) between Long Island and MA and retrograde back inland.

Rain Map:



The onshore flow in combination with the heavy rainfall rates means coastal flooding will be an issue. Not to mention the already saturated grounds from previous rainfall events, and this could spell flash flooding to flood prone areas located within the orange region of the map. Fortunately, while this storm will hang around the northeast region over 3 days, dry air is expected to works its way in and cut off the rain. Still, please be aware of the situation and know that heavy rainfall is expected through much of the day on Tuesday.




Snow Map:



Once the storm deepens and cuts off from the flow, that is going to help usher in colder air into interior parts of the northeast. Furthermore, a CCB band is going to develop between central and east-central PA through central and north-central NY. Those are the areas, especially in highest elevations, that can expect significant snowfall accumulations to occur. There is a slight chance late Wednesday night into Thursday that enough cold air makes it toward the coast and they see some snow showers as well, but their biggest threat will be the heavy rainfall on Tuesday.

Wind Map:



With an onshore flow and a deepening storm coming up the coast, winds will be a cause for concern for some areas, especially Long Island where gusts could exceed 50-60 mph at times. With a surface low located about 100 miles off our coast (remnants of Saturday's storm) and a strong piece of upper level energy phasing in, this will allow 925 mb winds to get to higher than normal levels along the immediate coast. On a side note, winds up in eastern Canada where the low interacts with the HP will see gusts as high as 60-70 mph! Impressive to say the least.

Timing:

Start: 5-7am Tuesday

Heaviest Precip: 11am-4pm Tuesday

End: 7-9pm Tuesday with lingering clouds, rain/snow showers possible through Thursday. This is when minor accumulations could be possible for areas just north and west of NYC. A coating in and around the city can not be ruled out either.

The models are still struggling with the location of where the surface low tracks, but since coastal storms this season so far seem to take the low pressure just west of the BM, that is the track I am going with. It is possible I update these maps tomorrow before the storm hits.

Nice write up I had to stay up to read this : ) Not gonna stay for Euro, I told u about the winds lol, do you think high wind warnings may be issued if the higher levels are met, you do have me in the highest part of the storm except the snow, oh well we cannot have everything. I will try to get out there and get some wind readings if the rain doesn't totally blind me lol. When do you expect the highest winds to be?

On another note I think you have this nailed, if anything it will be stronger IMO, but I do not think it will bust low. And its probably inferred but with the saturation in my area down pretty deep, with the winds power outages from uprooted trees could be a problem (maybe some broken branches but that seems less likely unless the wind gets 45-60. Is this where you want the storn discussion to continue tomorrow?

jmanley32 wrote:Nice write up I had to stay up to read this : ) Not gonna stay for Euro, I told u about the winds lol, do you think high wind warnings may be issued if the higher levels are met, you do have me in the highest part of the storm except the snow, oh well we cannot have everything.  I will try to get out there and get some wind readings if the rain doesn't totally blind me lol. When do you expect the highest winds to be?

I am trying to figure out why there are no high wind watches out right now.

Me too right? NWS says advisories may be needed for LI, personally my best buess is high wind warnings will be in effect from southern westchester, coastal northern NJ, NYC, LI, coastal CT, RI and MA.

jmanley32 wrote:Me too right?  NWS says advisories may be needed for LI, personally my best buess is high wind warnings will be in effect from southern westchester, coastal northern NJ, NYC, LI, coastal CT, RI and MA.

Would not surprise me. 925 mb winds look very impressive.

Look at 00z NAM

I added to the post above about trees possibly toppling after your reply. My only guess is NWS is being cautious as high wind watches/warnings get people really worried about ie power outages and they want to wait till tomorrows 12z. This is sure complex and I so wish I didn;t have to work Tuesday lol, I would be Jim Cantore out there lol, maybe I can sneak away for a bit around the afternoon when the worst seems to be.

And what does 925 equate to down on the surface, and I know due to the heavy rain they will be able to mix down easily so is it the same strength cause damn thats easily 60mph for my area and LI could see 70 if its just right. Crazy, imagine if this were all snow, Frank I can only hope we have a repeat in the dead of winter.

Oh shit and those are kts damn!

925 mb is about 2500 feet up in the air

850 mb is 5,000 feet. I always remember to take half for 925 mb. I forgot who taught me that. 1000mb is surface

That can't be right is it? 850mb winds are higher in the air per a discussion I had with ryan maue on wxbell and that was like 1500 ft for 925mb, so what I was asking was are those numbers you make on your maps factoring in that NAM map? You staying for Euro its so close I might as well stay with ya.

wait somewhere I have a grid that explains this, I believe you but I just want to look and see if I can find it.

jmanley32 wrote:That can't be right is it? 850mb winds are higher in the air per a discussion I had with ryan maue on wxbell and that was like 1500 ft for 925mb, so what I was asking was are those numbers you make on your maps factoring in that NAM map?  You staying for Euro its so close I might as well stay with ya.

Yea, 850 mb is higher.

850 mb = 5,000 ft up in the air

925 mb = 2,500 ft up in the air

1000 mb = near surface (not many outlets show this)

Iv'e made it this far...mine as well stay up for EURO

did u see sref sustained 10m winds from earlier this evening damn!

where did u get that 925mb wind map for NAM? 12z Euro had surface gusts at a 12 hr period of gusts from 50-60kts for area from me out to LI (higest being LI), the 50 was right over me which is almost 60mph

Euro coming in strong, looks beastly.

Where do you ant posts to go for this from now on I realized this is the map section u want posts continued on the other page?

One of my fav websites

http://weather.cod.edu/forecast/

Also like twisterdata.com

Bookmark both

jmanley32 wrote:Where do you ant posts to go for this from now on I realized this is the map section u want posts continued on the other page?

Was that english?

LOL hey man I am tired too, do you want posts to go here on the storm or back on the other thread?

Maybe some snow showers Wed. morning per EURO. No accumulations for NYC

jmanley32 wrote:LOL hey man I am tired too, do you want posts to go here on the storm or back on the other thread?

Oh, haha. Here is good. We'll start observation thread tomorrow night

ok, euro snow map is high already at hr 54 jeeze, if this happens you'd better up your totals.