ATL: NICHOLAS - Post-Tropical - Discussion

[GCANE]

Seeing some warm-core features on IR

[cycloneye]

Showers and thunderstorms associated with a broad area of low
pressure over the southwestern Bay of Campeche have increased
overnight and are showing signs of organization. Environmental
conditions are conducive for additional development, and a tropical
depression is expected to form later today or tonight while the
system moves northwestward and then northward near the coast of
northeastern Mexico. Additional development is possible through the
middle of next week if the system remains over water, and interests
along the western and northwestern Gulf coast should monitor the
progress of this disturbance as watches may be required for portions
of the coasts of northeastern Mexico and Texas later this morning or
this afternoon. An Air Force Hurricane Hunter aircraft is currently
en route to investigate the system this morning.

Regardless of development, the disturbance will continue to produce
heavy rain across portions of southern Mexico today, which may lead
to flash flooding and mudslides. By late today, heavy rain is
expected to reach portions of the Texas and Louisiana coasts, with
a heavy rain threat continuing across those coastal areas through
the middle of the week. Localized significant rainfall amounts are
possible, potentially resulting in areas of flash, urban, and
isolated river flooding.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.

[wxman57]

Still looks like a moderate TS moving inland between Brownsville & Matagorda Bay Monday afternoon to Tuesday morning. GFS & EC indicate 30-40 kt westerly winds aloft across the upper TX coast and northern Gulf. The stronger it gets, the farther east it tracks but the more shear it encounters. If it stays weaker, then it tracks inland closer to Brownsville. Since it will be moving parallel to the coast, a minor track change means a significantly different point of landfall. Hoping to get some rain for my dry yard here in Houston. Could see 5-10".

I doubt that this morning's recon will tell us anything that we don't already know. Might find a broad weak circulation forming that doesn't qualify for TD. It's what happens tomorrow that matters more. I'm surprised the NHC hasn't initiated PTC advisories already. It's now less than 36 hours before possible TS winds NE MX or Brownsville. Consensus says Matagorda Bay. That's what their PTC track will show this morning. I assume they'll issue one by 15Z.

[GCANE]

I got a feeling this one may have a surprise or two up its sleeves that the models aren't really picking up on.

[Stormcenter]

Agree

I got a feeling this one may have a surprise or two up its sleeves that the models aren't really picking up on.

[NDG]

I am 50/50 that the recon will find a well defined circulation for it to qualify as a TD, this afternoon would had been a better chance.
The GFS has been persistent during the past 4 runs of landfall in SW LA.
SHIPS model shows wind shear under 20 knots over the next 36 hrs while tracking over 30 C SSTs.
I wouldn't doubt it gets to at least a strong TS if not a weak Cat 1 before the dry air and stronger shear gets to it further north.

[GCANE]

Recon currently flying at 25K ft and flight level winds are very light.

[GCANE]

In the last 2 hours I have seen two high-helicity hot towers fire off.

[aspen]

The UL setup will provide some good ventilation for 94L during the next 36-48 hours, assuming it stays over water for that amount of time. 55 kt seems like a reasonable estimate for the low end of possible peak intensities, while 80 kt seems like a good high end estimate. You can never trust a system with 24 hours or more over 30C Gulf waters with low shear, but thankfully 94L probably won’t have enough time to truly bomb out, and the UL flow will probably cause it to weaken before landfall.

Dry air probably won’t be an issue until early Tuesday when the UL flow shifts to the east. Until then, upper and low-level flow will be coming from the south, and 94L is embedded in a large swath of moisture. It’ll take the high shear of the UL jet to thrust any dry air into this.

[GCANE]

Hot Tower at 21N 94W looks pretty darn good with lots of lightning.
Let's see if recon takes a dive into it.

[GCANE]

Recon is closing in on the tower and descending

[GCANE]

Flight Level winds picking up dramatically as recon descends.
Could be a TS if they find west winds.

[NDG]

Indeed it is already finding TS force winds on the NE quadrant, like ASCAT showed last night.

131030 2148N 09308W 9582 00470 0107 +232 +230 127036 039 030 001 00
131100 2146N 09309W 9605 00446 0105 +232 +224 131037 038 038 004 00
131130 2144N 09308W 9600 00446 0102 +233 +212 131040 043 041 001 00
131200 2143N 09308W 9594 00453 0104 +226 +207 135044 044 038 003 00
131230 2141N 09307W 9597 00450 0103 +222 +209 134043 044 039 001 03

[GCANE]

Recon levelled off at 960 mb with unflagged SFMR at 38 knts

[NDG]

Still flying straight south.
Edit: A heading towards the SW in the last couple of minutes.

URNT15 KNHC 121322
AF303 01DDA INVEST HDOB 16 20210912
131300 2140N 09307W 9596 00449 0103 +216 //// 134040 043 038 003 01
131330 2139N 09307W 9597 00450 0104 +216 //// 135040 041 039 002 01
131400 2137N 09306W 9633 00424 0109 +218 //// 136038 039 039 001 01
131430 2136N 09306W 9698 00359 0105 +223 //// 136037 039 038 001 01
131500 2135N 09305W 9707 00349 0104 +225 //// 139038 039 038 002 01
131530 2134N 09305W 9694 00365 0105 +223 //// 142037 038 037 001 01
131600 2133N 09305W 9702 00357 0105 +225 +222 142036 037 036 003 00
131630 2131N 09304W 9694 00364 0105 +225 //// 145033 035 033 002 01
131700 2130N 09304W 9703 00357 0106 +225 //// 145034 035 033 001 01
131730 2129N 09304W 9695 00362 0105 +225 //// 145034 034 031 001 01
131800 2127N 09304W 9700 00358 0104 +228 +228 145034 035 031 002 00
131830 2126N 09304W 9694 00364 0105 +226 //// 144032 034 031 002 01
131900 2125N 09304W 9702 00351 0103 +231 +227 149035 036 031 002 00
131930 2123N 09304W 9697 00359 0103 +229 //// 150033 036 033 000 01
132000 2122N 09304W 9696 00359 0103 +229 //// 149033 034 033 001 01
132030 2121N 09305W 9695 00359 0103 +230 +226 148034 035 028 000 00
132100 2120N 09306W 9700 00359 0105 +230 +226 147033 035 029 001 00
132130 2119N 09307W 9701 00357 0104 +230 +223 151034 035 029 001 00
132200 2118N 09309W 9703 00356 0105 +229 +227 150033 034 029 002 00
132230 2117N 09310W 9691 00366 0104 +229 //// 150032 034 030 002 01
$$
;

[aspen]

Plenty of 35-40 kt surface winds. This’ll be TS Nicholas the moment they find a closed circulation.

[GCANE]

Looking good so far
Could be a tight one.

[wxman57]

Needs a circulation to be upgraded. Tropical waves often produce TS winds in the squalls.

[underthwx]

Still looks like a moderate TS moving inland between Brownsville & Matagorda Bay Monday afternoon to Tuesday morning. GFS & EC indicate 30-40 kt westerly winds aloft across the upper TX coast and northern Gulf. The stronger it gets, the farther east it tracks but the more shear it encounters. If it stays weaker, then it tracks inland closer to Brownsville. Since it will be moving parallel to the coast, a minor track change means a significantly different point of landfall. Hoping to get some rain for my dry yard here in Houston. Could see 5-10".

I doubt that this morning's recon will tell us anything that we don't already know. Might find a broad weak circulation forming that doesn't qualify for TD. It's what happens tomorrow that matters more. I'm surprised the NHC hasn't initiated PTC advisories already. It's now less than 36 hours before possible TS winds NE MX or Brownsville. Consensus says Matagorda Bay. That's what their PTC track will show this morning. I assume they'll issue one by 15Z.

Thx for the excellent update

[cycloneye]

 https://twitter.com/cyclonicwx/status/1437048165828546568