[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 100843
TCDAT3

Hurricane Lee Discussion Number  20
NWS National Hurricane Center Miami FL       AL132023
500 AM AST Sun Sep 10 2023

Lee still seems to be feeling the effects of moderate southwesterly
wind shear, dry air, and internal structural changes.  An Air Force
Reserve Hurricane Hunter aircraft reported earlier that the eyewall
had deteriorated to only a few curved bands.  Geostationary
satellite imagery and earlier dropsonde data suggested that some dry
air is wrapping around the eastern and northern portion of the
circulation. The aircraft found maximum surface winds of 86 kt, and
a minimum central pressure of 957 mb.  The initial intensity is held
at a possibly generous 90 kt based on these data.

The hurricane is moving to the west-northwest at 8 kt on the
southern side of a mid-level high pressure system.  The high is
expected to build west-southwestward over the next day or so, which
should slow Lee's forward speed.  By mid-week, a mid-latitude trough
is forecast to weaken the ridge and gradually turn Lee northward.
Global models differ significantly in the forward speed of the
hurricane, especially by the end of the forecast period. The
official track forecast is similar to the previous advisory and
generally favors the slower guidance, lying between the HCCA and
TCVN consensus aid.

A satellite analysis product from UW/CIMSS indicates that there is a
gradient of moderate-to-strong southwesterly shear over Lee.  This
product suggests that the GFS, which is analyzing lower values of
shear, may not be accurately representing the environment near the
hurricane.  Still, most of the model guidance predicts the shear
should relax, allowing Lee to strengthen in the next 36-48 h.  The
latest intensity forecast has been lowered slightly from the
previous advisory, now showing a peak intensity of 115 kt.  Beyond
day 2, environmental and oceanic conditions are expected to become
less conducive and cause Lee to gradually weaken.  The NHC track
forecast remains in the middle of guidance envelop, 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 early this
week.

2. Dangerous surf and life-threatening rip currents are affecting
portions of the northern Leeward Islands and Puerto Rico.  These
conditions are spreading westward and northward and will affect
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, especially 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 soon and continuing through the week as Lee
grows in size. Users should continue to monitor updates to the
forecast of Lee during the next several days.


FORECAST POSITIONS AND MAX WINDS

INIT  10/0900Z 21.4N  60.5W   90 KT 105 MPH
 12H  10/1800Z 22.0N  61.5W   95 KT 110 MPH
 24H  11/0600Z 22.8N  62.8W  105 KT 120 MPH
 36H  11/1800Z 23.3N  64.0W  115 KT 130 MPH
 48H  12/0600Z 23.6N  65.2W  115 KT 130 MPH
 60H  12/1800Z 23.9N  66.1W  110 KT 125 MPH
 72H  13/0600Z 24.5N  66.9W  105 KT 120 MPH
 96H  14/0600Z 26.5N  68.0W   95 KT 110 MPH
120H  15/0600Z 30.2N  68.0W   80 KT  90 MPH

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