000
WTNT44 KNHC 130850
TCDAT4
Tropical Storm Nicholas Discussion Number 5
NWS National Hurricane Center Miami FL AL142021
400 AM CDT Mon Sep 13 2021
Radar data from Brownsville shows that the center of Nicholas is on
the southwestern side of a large area of deep convection over the
western Gulf of Mexico. While southwesterly shear continues to
affect the storm, the radar presentation has recently improved,
with what could be the start of a partial eyewall forming in the
northern quadrant. The initial wind speed remains 50 kt based on
earlier aircraft flight-level winds of 59 kt, believable SFMR
values up to 50 kt, along with radar winds at 5000 ft near 60 kt.
The storm is moving north-northwestward at about 12 kt. Nicholas is
forecast to turn northward soon into a weakness in the subtropical
ridge. The track prediction is only nudged slightly westward from
the previous one through landfall, consistent with recent model
guidance. Thereafter, there isn't good agreement among the models
on how quickly the tropical cyclone will move northeastward out of
Texas. Generally the models are faster this cycle, which seems
believable given the large northward re-formation earlier likely
exposing Nicholas to stronger mid-latitude flow. Thus the new NHC
forecast is trended faster as well, but remains behind the model
consensus. Obviously the forward speed is important to the heavy
rainfall forecast, and this trend will be one to watch.
Nicholas should continue to strengthen up until landfall due
primarily to the very warm Gulf waters and the recent inner-core
improvements. Moderate southwesterly shear and some dry air are the
main inhibiting factors and will hopefully keep the strengthening in
check. However, it is possible that Nicholas could become a
hurricane before landfall, and that's the reason for the hurricane
watch area. Nicholas should weaken after landfall, diminish into a
tropical depression within a couple of days, and degenerate into a
remnant low in about 3 days. No significant changes were made to
the previous NHC wind speed prediction.
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 considerable flash
and urban flooding, especially in highly urbanized metropolitan
areas. Isolated minor to 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 San Luis 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 today, and could be near hurricane
intensity at landfall. Tropical storm conditions are expected
along portions of the middle Texas coast beginning by this
afternoon, with hurricane conditions possible from Port Aransas to
Freeport this afternoon and tonight.
4. Tropical storm conditions are expected along portions of the
northeastern coast of Mexico and the coast of south Texas beginning
during the next few hours.
FORECAST POSITIONS AND MAX WINDS
INIT 13/0900Z 25.5N 96.6W 50 KT 60 MPH
12H 13/1800Z 27.3N 96.8W 60 KT 70 MPH
24H 14/0600Z 29.2N 96.5W 45 KT 50 MPH...INLAND
36H 14/1800Z 30.6N 95.8W 35 KT 40 MPH...INLAND
48H 15/0600Z 31.5N 94.5W 30 KT 35 MPH...INLAND
60H 15/1800Z 32.1N 93.0W 25 KT 30 MPH...INLAND
72H 16/0600Z 32.5N 91.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 17/0600Z...DISSIPATED
$$
Forecaster Blake
