mid-Atlantic coast potential subtropical storm development sometime between Sept 28-Oct 1?

[wdrag]

Uncertainty but I think there will be substantial northeast-east isobaric gradient developing sometime in this time frame with tides starting out 1/2-3/4 foot higher than than that of current Ophelia impact.  This combined with the continued daily constancy of onshore flow that began Sept 22 for NJ-DE-MD suggests to me increased beach erosion-coastal flooding """potential"""" beyond that of Ophelia  Questions: If this low pressure system does form, can it muster subtropical characteristics and la-lo track of the center.  Worthy of monitoring. Right now I can't grab anything from the FSU web site to check phase diagrams.

 

I added the EPS 24 hr QPF ending Saturday morning suggesting something going on late this coming week.

[Amped]

Hopefully not. Don't need 2 weekends in a row ruined. Hopefully the gfs is overdone withe the wind.

[jbenedet]

Fascinating if nothing else.

This is the remnants of Ophelia. Not sure if it will be captured by the NHC as such; but the surface low is clearly associated with it across guidance. Very weak signature, as modeled, but upside potential is if the surface vort stays more robust; could spin something up a lot faster than current guidance consensus. 

[jm1220]

1 hour ago, wdrag said:

Uncertainty but I think there will be substantial northeast-east isobaric gradient developing sometime in this time frame with tides starting out 1/2-3/4 foot higher than than that of current Ophelia impact.  This combined with the continued daily constancy of onshore flow that began Sept 22 for NJ-DE-MD suggests to me increased beach erosion-coastal flooding """potential"""" beyond that of Ophelia  Questions: If this low pressure system does form, can it muster subtropical characteristics and la-lo track of the center.  Worthy of monitoring. Right now I can't grab anything from the FSU web site to check phase diagrams.

 

I added the EPS 24 hr QPF ending Saturday morning suggesting something going on late this coming week.

Ugggh  not again. But thanks as always for the analysis Walt. 

[Eskimo Joe]

Bring it on. We need the rain and It would be interesting to see Ivan 2.0.

[wdrag]

More background...

 

Ophelia leaves behind an impression at the surface, but a new short wave cutting across CHIcago 12z Wed, sort of gets absorbed into the remnant trough aloft off the mid Atlantic coast with subsequent building heights in southern Canada forcing the trough to become stronger and possibly sag west or southwest. 

 

Upwelling from recent Tropical systems still leaves behind 70+SST off the mid Atlantic coast, and with the system lingering over those 70+SST waters Oct 1... I could see this starting to transition to at least partial warm core, if not Sunday..maybe Monday or Tuesday. 

Hope this is of value.  Don't like wasting time. I see 12z Modeling keeps this option open.  Right now, it's further south than I anticipated.  However, if this does go subtropical and lingers long enough over those waters, it eventually heads north or northeast. 

Anyway,  I think it bears monitoring and I wouldn't put away the sand shovels yet along the waterfronts, nor leave my car parked near the break wall, thinking this weekend was the worst.  Just don't know. 

•  

[Normandy]

I don’t see too much potential with this one beyond Ophelia.  I see potential for a subtropical storm but not something of hurricane strength because of cooler waters and this coming in at a higher latitude.  Will def still track though.  The season of east coast lows continues!

[MattPetrulli]

[GaWx]

 I don’t know whether or not this is related to this thread’s idea of an offshore Mid-Atlantic formation within 4-7 days because it is further S, but I’m posting the 12Z UKMET just in case. The 12Z UKMET has a TC form just offshore the SE US on Thu (9/29) followed by very slow E movement for 3 days due to the blocking high sort of keeping it stuck:

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 102 HOURS
              FORECAST POSITION AT T+102 : 32.2N  78.8W

                        LEAD                 CENTRAL     MAXIMUM WIND
      VERIFYING TIME    TIME   POSITION   PRESSURE (MB)  SPEED (KNOTS)
      --------------    ----   --------   -------------  -------------
    0000UTC 29.09.2023  108  32.5N  77.1W     1011            29
    1200UTC 29.09.2023  120  33.3N  76.6W     1010            29
    0000UTC 30.09.2023  132  34.8N  75.0W     1010            32
    1200UTC 30.09.2023  144  34.4N  74.1W     1009            36
    0000UTC 01.10.2023  156  33.4N  73.4W     1007            34
    1200UTC 01.10.2023  168  33.1N  72.4W     1005            34

[Normandy]

Looking at the GFS vs Euro, Phillipe and 91L hold the key to the future of this system in my opinion.  The Euro is sending both aforementioned systems much further west.  if the Euro is correct there are too many players on the field for this subtropical system to develop.  if the GFS is correct and both 91L and Philippe recurve together, that opens up the western basin for this subtropical system.

[wdrag]

Have waited this out and so as a NON-expert in tropical storm genesis... but using extra tropical ensemble upper air guidance and the surface response off the mid-Atlantic coast late this week, I think we'll see a significant low roughly 37/72 by 12z/30, meander east-then south or south-southwest in the following days and go through a phase change over the warmer SST's between Oct 1-3. I'll leave it at that since I'm not an expert but I think the western Atlantic is interesting, not only from the cold core development 29th-30th, then thereafter the possible evolution the first week of October. Just looks to me like the door is open off the southeast-mid Atlantic coast first week of October. I don't know how the currently modeled tropical systems south central Atlantic play into this. 

[NorthHillsWx]

All I’ll say is this parade of coastal storms better continue into the winter…

[wdrag]

NON TS expert comment. Just using guidance. Will review much more closely on the 29th when our low pressure off the mid Atlantic coast is becoming better defined. All I see on FSU multi global model phase diagrams(00z/28) is opportunity to become a warmer core by Oct 1, with track Oct 1 onward having opportunity to drift south to southwest but still well off the Carolinas. For now it's nothing and good to keep a lid on what I see is as a meandering potential tropical system early next week off the se USA coast.  If this does happen, then it eventually picks up in a NNE track by the 7th. Still of interest for me...but thinking will know much more late Friday on it's potential evolution to a warmer core.   Just need to monitor. 8A/28.

[wdrag]

So what I'm following in the modeling this weekend and to whatever it is or isn't early next week.

Attached 48 HRRR satellite and gust prediction--a model individual cycle snapshot for 18z Saturday Oct 30.  Gusts probably 10 MPH too high at 48 hours but worthy of monitoring?

 

[wdrag]

Letting this die away quietly. Still keeping an eye off the se USA coast later this week but for now... nothing.   If something got going out there, there would be a chance for something weak to sweep north toward the benchmark. For now, not modeled.  

Of interest, the value of differing contributing factors to big events. 9/29 NYC for example... pathetic weak surface low, but right amounts of instability, concentrated inflow lift for 18 hours and PW near 1.7". Yield-impact was pretty large there, in case you missed the news for the top 10 daily rainfall JFK, NYC CP. 

[jbenedet]

1 hour ago, wdrag said:

Letting this die away quietly. Still keeping an eye off the se USA coast later this week but for now... nothing.   If something got going out there, there would be a chance for something weak to sweep north toward the benchmark. For now, not modeled.  

 

yea I agree this window is interesting. But I’m seeing more tropical than stc interest this time. For one you can see it in the short term forecasts—weather in Easter CONUS more akin to late summer than early fall. Dews and 80’s are back; the tapestry has shifted to summer.

Currently very low odds, but a few members of the GEFS show Phillipe with a much later recurve and interacting with the deep CONUS trough later week. Phillip is currently far south and weak enough to miss the early recurve altogether, and continue along the easterlies.