Another big Sept rain event between roughly midnight Friday morning and midnight Sunday morning (bulk 9/29-30/2023)

[wdrag]

Periods of rain, some of it heavy at times is destined for most of the NYC subforum Friday-Saturday as low pressure develops off the mid Atlantic coast into a vertically deep slow moving cyclone. PW increases at times to near 1.7" in warm advection along the inverted trough Friday then the pinwheeling PWAT circles back around our area Saturday. Gusty northeast-east winds  Friday morning to 35 MPH and the constancy of northeast flow this week at the time of the highest tides in Sept should yield at least minor coastal Flooding within 2 hours of high tides Friday and possibly moderate coastal flooding at the highest tide cycle Saturday or Sunday as the backwash of the offshore storm shoots some 45 MPH north-northeast winds down the NJ coast by Sunday morning. 

The previous 3-4 day rains are attached, and the numbers for this coming one may exceed 6" again in parts of the NYC subforum.  If so, where?   It's possible, despite all this projected rain, that flooding might be imited to a few small areas. Too early to be sure as of 447PM/27.

The EPS has been most aggressive with this system since 9/24 cycles and the 12z/27 EPS mean rainfall is attached.  These values are quite high and much higher than the GEFS 12z/27 cycle with the GEPS midway between.  If it causes fresh water flooding---where?  Not sure this will be very much freshwater flooding except possibly NJ/CT/urban LI. 

This topic should serve also for the rainfall reports.

 

at 505PM added the tag power outages.  If this rainfall develops per the more aggressive 12z/27 EPS mean, rain softened ground from this past weekend combined with new 2+" rainfall may allow spotty power outages due to tree uproots of still fully leaved trees. 

[brooklynwx99]

Friday is concerning... persistent onshore flow leading to massive FGEN banding. as the banding pivots, it appears there is the potential for 2-4" amounts or greater, but who knows where the banding will set up. it's similar to a Norlun in that regard

classic sloped FGEN with potent 700mb omega. kinda similar to something you'd see in the winter

ENS and mesos are in agreement, and given the lead time of only two days, it appears like a significant flooding event is gaining traction

[Stormlover74]

1 minute ago, brooklynwx99 said:

Friday is concerning... persistent onshore flow leading to massive FGEN banding. as the banding pivots, it appears there is the potential for 2-4" amounts or greater, but who knows where the banding will set up. it's similar to a Norlun in that regard

classic sloped FGEN with potent 700mb omega. kinda similar to something you'd see in the winter

ENS and mesos are in agreement, and given the lead time of only two days, it appears like a significant flooding event is gaining traction

Yep the only question is where. Rgem is focused further east than the nams and hrrr

[Allsnow]

7 minutes ago, Stormlover74 said:

Yep the only question is where. Rgem is focused further east than the nams and hrrr

Rgem still pretty wet 

 

 

[Stormlover74]

1 minute ago, Allsnow said:

Rgem still pretty wet 

 

 

Yeah but 1 to 2 big difference from 6 to 8

[Allsnow]

5 minutes ago, Stormlover74 said:

Yeah but 1 to 2 big difference from 6 to 8

Icon over nyc 

[mob1]

4 minutes ago, Allsnow said:

Icon over nyc 

Yep, looks like a more realistic version of the NAM. 

[Superstorm93]

RRFS Ensembles (new HREF soon) all show significant events...just depends where at this time

 

 

[Stormlover74]

[qg_omega]

Upton not impressed

&& .HYDROLOGY... Rainfall from Thu night into Sat somewhat uncertain. Areas from NYC north/west and across SE CT/eastern Long Island appear most likely to see at least 1-1.5 inches. A stronger offshore trough/low could Fri into Sat could result in heavier rain of over 2 inches for parts of SE CT/eastern Long Island. Duration of this rainfall should limit any hydrologic impact.

 

[nycwinter]

maybe we can go over 10 inches for the month with this event..

[Rtd208]

This is something I said back on Monday. Some of the rainfall amounts being put out by the models are very concerning but tough to pinpoint.

[winterwarlock]

Mt holly doesn't  seem bullish as they are forecasting  just half inch to inch

[wdrag]

29 minutes ago, winterwarlock said:

Mt holly doesn't  seem bullish as they are forecasting  just half inch to inch

I think our WFO's tend to stay close to WPC beyond 12 hours... one NWS voice. They also had the conservative GEFS on their low side.  Just saw the 18z EC OP... continues bullish-attached.  Uncertainty with RRFS/NAM tending more NYS or west of NYC, while EC is definitely east of RRFS.  Time to iron this out and also figure the confidence of seeing any 6's.

 

NWS Blend of Models also much less than EC/EPS, GEPS, RRFS/NAM. 

Walt

[psv88]

Don’t even need to look at models. City west will get 9”, LI .5”. Book it 

[forkyfork]

10" max in nnj on the hrrr

[jm1220]

4 minutes ago, psv88 said:

Don’t even need to look at models. City west will get 9”, LI .5”. Book it 

We can always lean on the ol’ inverted troughs usually end up east of forecasts 48hrs out line. But then it’ll lurch all the way east and hit Cape Cod. 

[MJO812]

[Stormlover74]

1 minute ago, MJO812 said:

And still going

[Brian5671]

Crazy if this even comes close to verifying...and agree the IVT trough rule-usually a bit N and E of model forecasts

[Stormlover74]

Rgem further north and east 

[MJO812]

[jm1220]

27 minutes ago, Stormlover74 said:

Rgem further north and east 

Definitely hope it's the 1.5" shown here and not the 6+ on other models. 

[Franklin0529]

21 minutes ago, MJO812 said:

I just had over 5" here in Monmouth county. This would be bad. The beaches at Sandy Hook have taken a beating

 

[NJwx85]

If the HRRR verifies the river flooding along the Passaic basin could approach Irene levels. Water levels are already way above normal.

[Big Jims Videos]

Nws forecast just updated for me 1-2 inches of rain Friday now - on top of what falls tonight and Friday night.  

That's a big upgrade and I suspect the next discussion should be lengthy. 

[Rtd208]

[jm1220]

6z HRRR, RGEM absolute soakers here. I’m hoping they’re overdone. Really anywhere but I guess worse in NJ and upstate where the rain’s been so much worse that kind of rain will cause big problems especially so quickly. 

[Allsnow]

 

[wdrag]

I'll add my 2c at 5P...  suggest mowing completed today. You may not like your soggy ground even on a rain free Sunday I84 corridor southward NJ-seNYS-SNE-LI. My guess is that NWS is waiting on any FFA because the GEFS/SREF/NAEFS are much more conservative than the GEPS-EPS 2-4" event and as you've all posted the iso 7" on highly resolved mesoscale guidance.  Also, NWS may be holding off due to no ensemble guidance showing minor flooding which is because these river forecasts use the ensemble output which seems to me wayyy too low. 

 

More at 5P after mowing.