ATL: NICHOLAS - Post-Tropical - Discussion

[ElectricStorm]

BULLETIN
Tropical Storm Nicholas Advisory Number 6
NWS National Hurricane Center Miami FL AL142021
1000 AM CDT Mon Sep 13 2021

...NICHOLAS MOVING ERRATICALLY NORTHWARD JUST OFFSHORE THE
SOUTHERN COAST OF TEXAS...
...FLASH FLOODING, DANGEROUS STORM SURGE, AND GUSTY WINDS EXPECTED
ALONG PORTIONS OF THE SOUTHERN AND MIDDLE TEXAS COASTS TODAY...


SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...26.4N 96.8W
ABOUT 45 MI...70 KM NE OF MOUTH OF THE RIO GRANDE
ABOUT 140 MI...225 KM S OF PORT OCONNOR TEXAS
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...N OR 5 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES

[tolakram]

000
WTNT44 KNHC 131436
TCDAT4

Tropical Storm Nicholas Discussion Number 6
NWS National Hurricane Center Miami FL AL142021
1000 AM CDT Mon Sep 13 2021

Doppler radar data from Brownsville and Corpus Christi, Texas, along
with reconnaissance aircraft flight-level wind data, indicate that
Nicholas' inner-core structure has undergone some radical changes
since the previous advisory. The earlier near-eyewall pattern
dissipated a few hours ago, and has been replaced with what appears
to be an ongoing reformation of a new center abut 90 nmi
north-northeast of the old center. The aircraft recently found a
pressure of 1000 to 1002 mb with the dissipating original center,
while Doppler radar velocity data show a pronounced mid- to
upper-level circulation forming farther north as previously
mentioned. The Air Force Reserve Hurricane Hunter aircraft is going
to be concentrating its reconnoiter mission in Nicholas'
northeastern quadrant to see if reformation of the low-level center
is occurring beneath the mid-level circulation noted in radar data.
The initial wind speed remains 50 kt based on recent aircraft 850-mb
flight-level winds of 59 kt, which equates to about 47 kt equivalent
surface winds.

The initial motion is an uncertain 005/10 kt due to the erosion and
ongoing reformation of the center. Despite the recent inner-core
erosion, the latest NHC model guidance remains in fairly good
agreement on Nicholas moving northward through a weakness in the
subtropical ridge. The GFS model has been performing exceptionally
well with predicting the recent erosion and more northward
reformation of the Nicholas' center. The new NHC track forecast is
similar to but slightly east or right of the previous advisory
track, and lies along the eastern edge of the track consensus model
envelope, which is to the left of the GFS track prediction.

Although the inner-core convective pattern has been disrupted,
recent trends in the radar data suggest that a new center should
reform farther northeast into the convective cloud shield. The
latest GFS- and ECMWF-based SHIPS shear analyses indicate that
westerly shear of near 20 kt is allegedly affecting Nicholas.
However, water vapor satellite imagery suggests that the upper-level
shear vector is actually from a south-southwesterly direction, which
is more along than across the cyclone's forward motion, thus
reducing the magnitude and negative effects of the vertical wind
shear. Therefore, strengthening is still expected until landfall
as Nicholas continues to move over slightly warmer Gulf waters. It
is possible that Nicholas could become a hurricane just before
landfall, and that's the reason for the northeastward extension of
the hurricane watch area. Nicholas should rapidly weaken after
landfall due to increased frictional effects, strong southwesterly
shear, and entrainment of mid-level dry air, resulting in
degeneration into a tropical depression by late Tuesday and a
remnant low on Wednesday. Otherwise, no significant changes were
made to the previous advisory intensity forecast.

Key Messages:

1. Heavy rainfall will impact portions of the Texas and Louisiana
coasts through the middle of the week. Significant rainfall amounts
are possible, potentially resulting in areas of life-threatening
flash and urban flooding, especially in highly urbanized
metropolitan areas. Minor to isolated moderate river flooding is
also expected.

2. There is the danger of life-threatening storm surge inundation
along the coast of Texas from Port Aransas to Sabine Pass.
Residents in these areas should follow any advice given by
local officials.

3. Nicholas is forecast to approach the middle Texas coast as a
strong tropical storm by this evening, and could be near hurricane
intensity at landfall. Tropical storm conditions are expected
along portions of the middle Texas coast beginning this afternoon,
with hurricane conditions possible from Port Aransas to San Luis
Pass by late afternoon through tonight.

4. Tropical storm conditions are expected along portions of the
coast of south Texas into the afternoon.

FORECAST POSITIONS AND MAX WINDS

INIT 13/1500Z 26.4N 96.8W 50 KT 60 MPH
12H 14/0000Z 27.5N 96.7W 60 KT 70 MPH
24H 14/1200Z 29.1N 96.3W 45 KT 50 MPH...INLAND
36H 15/0000Z 30.2N 95.4W 30 KT 35 MPH...INLAND
48H 15/1200Z 31.0N 94.0W 25 KT 30 MPH...INLAND
60H 16/0000Z 31.5N 92.5W 20 KT 25 MPH...INLAND
72H 16/1200Z 32.0N 91.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 17/1200Z...DISSIPATED

$$
Forecaster Stewart

[ElectricStorm]

The Storm Surge Warning has been extended from San Luis Pass to
Sabine Pass including Galveston Bay.

The Hurricane Watch has been extended northeastward to San Luis
Pass, Texas.

The Tropical Storm Warning has been extended eastward to Sabine
Pass.

The Storm Surge Watch from the Mouth of the Rio Grande to Baffin
Bay has been discontinued.

[LARanger]

I gotta say, as alarming as this potential flood factory is, the radar loop from this morning is utterly hilarious. It's like Nicholas was all "I'm goin' to Brownsville!" but, upon catching sight of the town, yeeted itself right the heck outta there with a right hearty "NOPE".

As I've said a few times, while 30 knots of shear isn't super high, it's apparently enough to push convection off to the east and disrupt Nicholas. This shear has been in the forecast for days too, though in the 40 knot range. Today will be a day for Nicholas to bump or stay sloppy. My bet is on sloppy ATM.

Well, yeah, obviously it's all the result of atmospheric effects, from the various causes of the center reformations (or attempts thereof) to the direct action of the shear at various levels. Just for science, I wouldn't mind if Nicholas puts on a little more of this hide-and-seek dancing show before petering out well before bothering anyone too much.

Literally Nicholas:

(Besides, if storms could decide where they went, anthropomorphically, a la my Brownsville joke, I think we all know there's no way any of them would come anywhere near Louisiana: "Oh sure, I'm a rotating mass of megatons of warm air, lightning, and excess moisture with a funky counter-rotating output chute stacked atop me, basically a monstrous swirling energy vampire drawing lifeforce from the warm water below, but even I'm not insane enough to roll up into that mass of voodoo cray-cray."

Of course, I could have the joke all wrong, and what actually happened is that Brownsville folk have the magic voodoo powers. In such a case, I'd just like to clarify that I wasn't making fun of Brownsville at all (please Brownsville don't hurt me).)

[GCANE]

62 mm/hr rain rate!
Definitely has the potential to go up a notch.

[HurricaneBrain]

I estimate new center is at 27N/95.3W per recon.

[tropicwatch]

I think the graphic folks might have oopps at the NHC. The new forecast cone position is way north of what the HH just reported. Unless I am missing something.

https://www.nhc.noaa.gov/storm_graphics/AT14/refresh/AL142021_5day_cone_no_line_and_wind+png/143722_5day_cone_no_line_and_wind.png

[tropicwatch]

I think the graphic folks might have oopps at the NHC. The new forecast cone position is way north of what the HH just reported. Unless I am missing something. The position also appears to be wrong in the latest advisory.

https://www.nhc.noaa.gov/storm_graphics/AT14/refresh/AL142021_5day_cone_no_line_and_wind+png/143722_5day_cone_no_line_and_wind.png

[tropicwatch]

Radar does indicate there is a center up there. We shall see when the HH comes south I guess.

[GCANE]

I am tempted to say a box of Cubans saz hurricane watch goes up for Galveston by the end of the day.

[xironman]

Nice to point out the relevance of relative shear

Although the inner-core convective pattern has been disrupted,
recent trends in the radar data suggest that a new center should
reform farther northeast into the convective cloud shield. The
latest GFS- and ECMWF-based SHIPS shear analyses indicate that
westerly shear of near 20 kt is allegedly affecting Nicholas.
However, water vapor satellite imagery suggests that the upper-level
shear vector is actually from a south-southwesterly direction, which
is more along than across the cyclone's forward motion, thus
reducing the magnitude and negative effects of the vertical wind
shear.

[GCANE]

Any big hot-tower will blow shear out of the water.
Could just happen based on the high rain rate recon is measuring.

[dpep4]

The most reformations since Hurricane Martin.

[ScottNAtlanta]

Looks like the GFS has beat the Euro again

[MBryant]

62 mm/hr rain rate!
Definitely has the potential to go up a notch.

That's about 2.5 inches/hour for those of us on the American System. Not quite so scary.

[capNstorms]

the circulation reformation was a tall tale that this was going to ramp up, expect a CAT 1 and hurricane warnings issued, this slow coast mover is going to cause some damage

[lrak]

https://www.ndbc.noaa.gov/station_page.php?station=42020

WOW!!!

[tolakram]

the circulation reformation was a tall tale that this was going to ramp up, expect a CAT 1 and hurricane warnings issued, this slow coast mover is going to cause some damage

tell tale? I think there's too much shear, but it will be a windy rainmaker for sure.

[jaguars_22]

Am I seeing more of a jog west?

[grapealcoholic]

New eyewall coming together

edit: not sure what recon is doing way up there? you can see the new eyewall coming together on radar..