[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 091444
TCDAT3

Hurricane Lee Discussion Number  17
NWS National Hurricane Center Miami FL       AL132023
1100 AM AST Sat Sep 09 2023

Satellite imagery shows that deep convection continues to pulse
near the center of Lee.  Recent reports from reconnaissance
aircraft and an earlier SSMIS microwave image indicates that Lee
has a small (5 to 10 n-mi-wide) eye that is obscured by the
higher convective cloud tops.  The NOAA P-3 Hurricane Hunter
aircraft penetrated the eye around 1013 UTC this morning and found
that the pressure was down a few millibars.  The NOAA aircraft
measured peak SFMR surface winds of 100 kt, and 700-mb flight-level
winds of 103 kt.   An Air Force Reserve reconnaissance aircraft
remains in the storm environment, but due to safety concerns was
not able to penetrate the northeastern eyewall on its first pass
through the storm due to very strong convection and mesovortices
orbiting the small eye.  A recent center drop from the Air Force
plane suggest that the minimum pressure is around 957 mb.  Drops
from both aircraft and Doppler radar data from the earlier NOAA
aircraft indicate that there is some southwest to northeast tilt
to the vortex.  Based on the aircraft data, the initial intensity
remains 100 kt for this advisory.

There is still some question as to how conducive the upper-level
environment will be during the next few days.  The GFS and regional
hurricane models indicate that the shear that has been affecting
Lee will decrease today, and that the upper-level wind pattern will
become much more favorable for restrengthening.  Meanwhile, the
ECMWF and UKMET models depict a less favorable environment, with a
continuation of at least some moderate shear.  The NHC forecast
follows the scenario that there will be at least some relaxation of
the shear and it calls for gradual restrengthening during the next
two to three days.  The official wind speed forecast is not as high
as some of the dynamical model guidance, but is a blend of the HFIP
corrected consensus model and the IVCN multi-model consensus.

Lee is still moving west-northwestward or 300/10 kt. A mid-level
ridge located over the central Atlantic is forecast to build
west-southwestward during the next few days.  This should keep Lee
on a general west-northwestward heading, but the building ridge is
expected to impede Lee's progress, and a much slower forward speed
is anticipated over the next several days. By Wednesday, Lee should
begin to turn northwestward, and then north-northwestward as a
mid-latitude trough moves into the Great Lakes region and eastern
United States.  While the cross track spread in the guidance
remains fairly low, there is significant long track (forward speed)
spread in the models.  The GFS and ECMWF depict similar overall
tracks, but the cross-track spread between those two typically
reliable models is more than 150 n mi by day 3. The NHC forecast
splits these speed differences and lies near the various consensus
aids.


KEY MESSAGES:

1. Lee's core is expected to move well north of the northern
Leeward Islands, the Virgin Islands, and Puerto Rico this weekend
and early next week.

2. Dangerous surf and life-threatening rip currents are affecting
portions of the northern Leeward Islands.  These conditions are
spreading westward and northward and will begin affecting Puerto
Rico, Hispaniola, the Turks and Caicos, the Bahamas, and Bermuda
later today and Sunday.

3. It is way too soon to know what level of impacts, if any, Lee
might have along the U.S. East Coast, Atlantic Canada, or Bermuda
late next week, particularly since the hurricane is expected to
slow down considerably over the southwestern Atlantic.  Regardless,
dangerous surf and rip currents are expected along most of the U.S.
East Coast beginning Sunday and Monday.  Continue to monitor
updates to Lee's forecast during the next several days.


FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 20.3N  58.2W  100 KT 115 MPH
 12H  10/0000Z 21.0N  59.3W  100 KT 115 MPH
 24H  10/1200Z 21.7N  60.6W  105 KT 120 MPH
 36H  11/0000Z 22.4N  61.9W  110 KT 125 MPH
 48H  11/1200Z 22.9N  63.1W  115 KT 130 MPH
 60H  12/0000Z 23.3N  64.2W  120 KT 140 MPH
 72H  12/1200Z 23.6N  65.3W  120 KT 140 MPH
 96H  13/1200Z 24.4N  67.0W  110 KT 125 MPH
120H  14/1200Z 26.8N  67.8W  105 KT 120 MPH

$$
Forecaster Brown
This weather bulletin was brought to you by:
www.nashvilleweather.net