[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 092036
TCDAT3

Hurricane Lee Discussion Number  18
NWS National Hurricane Center Miami FL       AL132023
500 PM AST Sat Sep 09 2023

Lee's satellite presentation has changed little today.  The center
is embedded within an area of cloud tops below -75C, and the Air
Force Reserve reconnaissance aircraft that was in the storm earlier
this afternoon continued to report that Lee has a small eye.
However, the eye remains obscured in both visible and infrared
satellite imagery. A blend of the flight-level and SFMR winds, as
well as dropsonde data from the earlier mission, yields an intensity
of around 100 kt, and the advisory intensity remains that value.
Dropsonde data in the center just before 1700 UTC supported a
minimum pressure of 958 mb. A NOAA P-3 aircraft is scheduled to be
in the storm environment again this evening to provide additional
information on the structure and strength of the hurricane.

Shear analysis from UW/CIMSS indicates that there is still about
15-20 kt of southwesterly shear over Lee.  The GFS continues to
suggest that the shear will lessen during the next couple of days,
creating a more favorable environment for Lee to strengthen.
However, the ECMWF and UKMET still favor the notion that the
upper-level wind pattern will not become quite as conducive for a
couple of more days.  Most of the intensity guidance calls for
gradual restrengthening and the NHC forecast follows suit.  The NHC
intensity forecast is close to the consensus models, but not as
high as some of the dynamical model guidance and the HFIP corrected
consensus.

Satellite and aircraft fixes show that Lee is moving west-
northwestward at about 9 kt. There has been no change to the track
forecast philosophy.  A mid-level ridge to the north of Lee is
foreast to shift west-southwestward during the next few days,
causing Lee's forward speed to slow considerably through early next
week.  By midweek, a mid-latitude trough moving across the Great
Lakes region and into the eastern United States is expected to
weaken the ridge and allow Lee to turn north-northwestward and
northward on days 4 and 5.  There is still a significant amount of
spread in the deterministic guidance and global model ensembles as
to exactly when and where the northward turn takes place.  In fact,
the GFS and ECMWF models are about 275 n mi apart at day 5,
primarily due to along-track spread related to how fast Lee begins
moving northward.  The NHC track forecast continues to lie near the
latest consensus aids, and the new track is very similar to the
previous forecast.

The center of Lee passed about 75 n mi south of NOAA buoy 41044 this
afternoon, and that buoy has reported peak 1-minute sustained winds
of 47 kt with a gust to 58 kt.  That data along with a couple of
earlier scatterometer overpass have shown that the tropical-storm
force wind field has expanded outward over the eastern semicircle,
and that has been reflected in the latest analysis and forecast.


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 affect Puerto Rico,
Hispaniola, the Turks and Caicos, the Bahamas, and Bermuda during
the next several days.

3. It remains 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. Users should continue to
monitor updates to the forecast of Lee during the next several days.


FORECAST POSITIONS AND MAX WINDS

INIT  09/2100Z 20.7N  59.1W  100 KT 115 MPH
 12H  10/0600Z 21.4N  60.3W  105 KT 120 MPH
 24H  10/1800Z 22.1N  61.6W  110 KT 125 MPH
 36H  11/0600Z 22.9N  62.9W  115 KT 130 MPH
 48H  11/1800Z 23.3N  64.1W  120 KT 140 MPH
 60H  12/0600Z 23.6N  65.3W  120 KT 140 MPH
 72H  12/1800Z 23.9N  66.3W  115 KT 130 MPH
 96H  13/1800Z 25.1N  67.8W  105 KT 120 MPH
120H  14/1800Z 27.9N  68.2W  100 KT 115 MPH

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