[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 040234
TCDAT1

Tropical Storm Earl Discussion Number   5
NWS National Hurricane Center Miami FL       AL062022
1100 PM AST Sat Sep 03 2022

There are no indications that Earl has strengthened further than it
did this afternoon.  The low-level center is a little difficult to
locate since it's obscured by high-level cirrus clouds, but it
appears to have moved out ahead of the deep convection again.  The
initial intensity remains 45 kt, and this fits a blend of the
latest Dvorak estimates of T3.5 and T2.5 from TAFB and SAB,
respectively.

Earl continues to move west-northwestward, or 285/9 kt, to the south
of a low- to mid-level ridge.  However, a break is developing in the
ridge over the western Atlantic, which should allow Earl to turn
northwestward on Sunday, followed by a recurvature toward the north
and northeast Tuesday through Thursday.  Although the track models
agree on this scenario, the biggest differences among them is the
along-track component, or how much Earl accelerates toward the north
and northeast on days 3 through 5.  Interestingly, both the GFS and
ECMWF ensemble means are well west and slower than their respective
deterministic runs, and the deterministic GFS in particular is an
extreme outlier and much faster than all other guidance by day 5
(likely because it carries a much stronger cyclone).  With so many
ensemble solutions slower and to the west, the updated NHC track
forecast is placed to the west of many of the multi-model consensus
aids, and it's just slightly west of the previous forecast.

The moderate to strong shear affecting Earl is unlikely to abate
through much of the forecast period.  Despite this shear, very warm
waters of at least 29 degrees Celsius and an unstable atmospheric
environment are expected to encourage gradual strengthening during
the next couple of days.  Then, around day 3, Earl could get an
additional positive boost from interaction with an upper-level
trough over the western Atlantic, and the official forecast shows
the system reaching hurricane strength by day 4 and intensifying
through the end of the forecast period.  It should be noted that a
few models show significant strengthening by days 4 and 5, but for
now the official forecast is conservative and is only nudged upward
toward the IVCN model consensus.

Tropical-storm-force winds are still forecast to remain on the
northern and eastern side of the circulation, and are not expected
to move across the northern Leeward Islands, the Virgin Islands, or
Puerto Rico.  However, gusty winds in squalls are possible at these
locations through Sunday.


KEY MESSAGES:

1.  Heavy rainfall from Earl is expected to lead to limited flash,
urban, and small stream flooding impacts over the Leeward Islands,
U.S. and British Virgin Islands, and Puerto Rico this weekend. Rapid
rises on rivers and mudslides in areas of steep terrain are possible
in Puerto Rico.

2.  Earl is forecast to pass to the north of the the Virgin Islands
and Puerto Rico overnight and on Sunday. Gusty winds, especially in
squalls, area possible on those islands through Sunday.


FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 19.5N  64.2W   45 KT  50 MPH
 12H  04/1200Z 20.0N  65.3W   45 KT  50 MPH
 24H  05/0000Z 20.9N  66.1W   50 KT  60 MPH
 36H  05/1200Z 21.7N  66.6W   50 KT  60 MPH
 48H  06/0000Z 22.7N  66.9W   55 KT  65 MPH
 60H  06/1200Z 23.5N  67.0W   60 KT  70 MPH
 72H  07/0000Z 24.3N  66.9W   60 KT  70 MPH
 96H  08/0000Z 25.6N  65.8W   70 KT  80 MPH
120H  09/0000Z 27.5N  63.6W   80 KT  90 MPH

$$
Forecaster Berg
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