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Tropical Storm NICHOLAS

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.
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