Coastal Storm 9/25/14

A couple of days ago, there were some signs on the models that a coastal storm may effect the area. The models kept keeping the storm off the coast, or showing a glancing blow, but there has been a sudden turn around in the last 12 hours that is bringing this storm right along the coast. Heavy rain will be the biggest factor with this storm, with some wind as well. 

12z GFS:



12z EURO:



One positive that we can take out of this is we can use the rain. It has been drier than normal for much of the area. Also, this will not be a strong storm. Most models project it between 1010-1020 mb, which is not strong at all. As you can see from the GFS / EURO, the heaviest will come Thursday morning, between 7am - 11am. 


Total rainfall map from the EURO is between 1.50-3.00 inches of rain. Judging by the current radar, these amounts are not out of the ordinary and I think 2-3 inches of rain could be the common range among most of the region. However, with additional models runs still to go, there is a chance this storm shifts east last minute and we avoid the heaviest rain, which would put us more in a 1-2 inch rainfall. 



Wind wise, we are probably looking at gusts between 20-30 mph, less the further west you live. East end of Long Island will be looking at 30+ mph wind gusts. Like I said before, this is a weak storm so I am not worried about the wind. It has a lot of moisture though, so it will be quite rainy. 

Timing:

Start: 2-3am Thursday 

End: 4-5pm Thursday (still uncertain with end time, will update again tomorrow morning)

Lots of moisture associated with this storm. If it shifts west some more, there could be places that see rain amounts in excess of 3 inches. I will keep a close eye as always.

Thanks Frank nice update, is there any chance this deepens more than expected? I mean it already changed alot or is that stretching it too far? A wind driven rain (even 20mph is enough to make umbrullas useless. I will be sure to leave extra early Thursday as gosh knows the roads here in NYC area will be hell.

Another thought, being there is tropical moisture involved is there the potential for t-storms or possible tornados? Frank good to see your back on with wx-bell, best graphics in my book, but I do like the other one you use, what is that called?

jmanley32 wrote:Thanks Frank nice update, is there any chance this deepens more than expected? I mean it already changed alot or is that stretching it too far?  A wind driven rain (even 20mph is enough to make umbrullas useless.  I will be sure to leave extra early Thursday as gosh knows the roads here in NYC area will be hell.

No, the upper air pattern is not condusive for a deepening storm. I do not even think there is much tropical activity involved with this storm. The 500mb maps show most of the energy coming in from the west. That is where the storm is getting most of its energy. 

jmanley32 wrote:Another thought, being there is tropical moisture involved is there the potential for t-storms or possible tornados? Frank good to see your back on with wx-bell, best graphics in my book, but I do like the other one you use, what is that called?

No severe weather expected. 

Yea, I just subscribed back to WeatherBell and StormVista

18z NAM bringing it west with alot of precip, but seems later than past runs its not even into NYC area by 12z on 25th.



Update: 18z NAM keeps most the precip south of NYC, I don't usually go by NAM though it has been ok before. We will see.

We have to watch the timing of when the HP moves east from the Great Lakes, it could supress it south and east....but with our track record in NENJ, it will go east!

Frank thanks fo r listening in starting a new thread - I had to run to my soccer game - back in it after 7 year hiatus - coaching that is not playing those days ended 20 years ago.

Bring on the pattern change with coastal's I say and Janet that HP is progged to weaken as it moves east if I am reading it correctly.

Gotta love the weather - hope this happens with winter - woop!!

18z NAm and GFS take it east and GFS have 2-5 inches of rain just offshore, one of you said you do not really trust the 18z though, any particular reason? Wonder what 00z will show.

I still do not trust this storm. Would not surprise me at all if it went east. There is a an arching ridge in the western US keeping the flow looking progressive. And as Janet mentioned, there is an HP near the Great Lakes sliding east which will also have an influence on this storms final track. That rolling ridge in conjuction with the HP leads me to believe the storm track will stay on the east side more than the west.

jmanley32 wrote:18z NAm and GFS take it east and GFS have 2-5 inches of rain just offshore, one of you said you do not really trust the 18z though, any particular reason?  Wonder what 00z will show.

That was me!! Mugs

Good news for most is that thursday most schools will have off for jewish holiday. So no worries on that traffic which, if you have been on the parkways these past 2 weeks, has been a nightmare on sunny days. Hope we get to see Jeter's last game at the stadium though.

frank when looking at the 500mb maps it's hard to believe that we could get so much rain from this system. there is a weakening closed/cutoff low over the Carolinas that rides up the coast. very little energy left when it reaches our area. the main player in this is the digging trough/closed low over the pacific n/w which forms a building ridge over the rocky mountains. this forces the moisture over the s/e which is tropical in nature to come due north into surface HP. this is only evidence (tropical moisture) I see in such high rainfall amounts with such a weak LP. almost looks like an overrunning event. wish I could post map but I am having trouble doing so. question can a 500mb HP close off like a LP does and if so is there one off the NC coast Thursday morning?

Euro 00z Wed
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GFS 00z Wed
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We are going to have to watch the satellites between Wed and Thursday to see if the ULL in the SE remains closed or opens up after being captured by the short wave.  
EURO 6z Thursday
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GFS 6z Thursday
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Notice that by 00z Friday the steering flow at 500mb is still NE on the Euro whereas its basically due east on the GFS.  
EURO 00z Friday
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As a result of still being closed at 500mb there still is a weak closed surface LP as well still drawing in moisture over LI and SE New England.  
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GFS00z Friday
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So the Key here is if the ULL over the SE CONUS stays closed or not and the timing of that as well.  Open vs closed I think depends on how much the shortwave digs and how fast it is.  The difference can be seen in the total precip maps.  Look at the sharp cutoff in the precip into our area between the two outcomes.  IMO this will boil down to observations on water vapor imagery come wed into Thursday.  You have to respect the Euro though.
EURO precip  
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GFS Precip
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If this sucker opens up early and the HP builds in from the west fast and furious we could see last minute totals decrease dramatically. Im stoked there is something to analyze.

Even though I am a Met fan, it would really be a shame if Jeter's final regular season game on Thursday gets rained out. ..

Math23x7 wrote:Even though I am a Met fan, it would really be a shame if Jeter's final regular season game on Thursday gets rained out. ..

Same here. Met Fan hoping this does not interfere with Derek Jeter's final home game.Hope he goes out blasting a home run or two for the Yankee Fans.

I am sure they will get this game in one way or another.  

Here are the precip totals 00z 's from last night.  00z EURO esp, came in a bit dryer; Although, 6zz GFS and NAM came in wetter than their 00z.  Notice the difference in ideas in the distribution of the precip.  The Euro and Nam have a swath of higher totals that extends up through SNJ and into PA and another swath off shore; whereas, the GFS and the CMC have sharp cutoffs to the west leaving the heavier precip at the coastline.  I think because there is somewhat of a disconnect between the weak closed 500mb LP and the weak surface LP leaving a void of lesser amts in the middle.  It looks like an area of increased vertical velocities combined with high relative humidity over PA will lead to higher totals in these areas as the Euro and NAM are showing.   Ill be at the game regardless.  
Euro
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NAM
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GFS
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CMC
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Scott - Great Analysis but one thing I am hoping for is a good soaking rain for the western parts of the NYC metro area - we need it!!

The 6Z GFS says so jogged west with precip amounts:

amugs wrote:Scott - Great Analysis but one thing I am hoping for is a good soaking rain for the western parts of the NYC metro area - we need it!!

The 6Z GFS says so jogged west with precip amounts:

As did the NAM.  Let it soak early, and be done by say 4pm.  Enough time to dry up th field.  I may be ambitious here

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Uptons take:
http://www.erh.noaa.gov/okx/stormtotalprecip.php

Right now I'm siding with models that have this further east, such as the GFS and CMC. I think the NAM is dead wrong. Will be interesting 12z model runs.

Looking at the upper air pattern, this is why I feel the storm will ultimately take a track following the black line I drew, or even further east than that (I kinda wanted to draw it a little further east). The pattern is fast-paced with a large trough entering the Pac. NW and a rolling ridge coming through the center of the country. Once the storm recognizes the High moving east, its track will get shunned east and dry air may try to eat away at the moisture on the western fringe of the storm. 

That being said, .50-1.00 inches of rain look most likely, but not those 2-3+ inch amounts some models were advertising yesterday.

It seems most of the models are slowing that HP down allowing for more rain, but I'll be waiting to see the 12z runs as well....

12z nam showing .5 to 1" for most areas except for the eastern half of Long Island where it shows more than 1 inch. I expect other models to come down with rainfall amounts and I agree with you Frank less than an inch of rain from this system. closer to a Half inch. actually northern half of New Jersey and hudson valley May see less than a half inch.