[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 041459
TCDAT1

Tropical Storm Earl Discussion Number   7
NWS National Hurricane Center Miami FL       AL062022
1100 AM AST Sun Sep 04 2022

This morning, Earl developed a large convective burst, with cold
convective cloud tops below -80 C and the larger cirrus plume
obscuring the low-level center. A NOAA-P3 mission has also be flying
through Earl this morning, showing that the center may be in the
process of reorganizing closer to this recent convective burst.
WSR-88D radar imagery from Puerto Rico earlier showed a well-defined
mid-level vortex associated with this convective burst up at 20 k
feet, which matched the NOAA-P3 TDR data, but it is unclear how
close the surface vortex is relative to this mid-level center.
Subjective Dvorak estimates from TAFB and SAB are T3.0/45-kt and
T3.5/55-kt respectively, though objective estimates are somewhat
lower, with ADT only at 33-kt and SATCON at 44-kt. A blend of these
estimates and the wind data from the NOAA-P3 mission support
maintaining the intensity at 45 kt for this advisory.

Earl appears to have slowed down further this morning, and may be in
the process of relocating closer to the convective burst, with the
latest motion an uncertain 310/3 kt. As mentioned previously, there
is a weakness in the mid-level ridging to the north of the storm,
and this should enable Earl to make a gradual turn to the
north-northwest and north over the next 24-72 hours. The mid-level
ridging then shifts mostly east of the cyclone, allowing a continued
slow north-northeastward motion thereafter. The latest track
guidance has shifted east in the short term due in part to the
initial position, and the latest NHC track forecast has been shifted
in that direction and lies just west of TVCN consensus. However, the
latest track forecast is not as far to the east as the HFIP
Corrected Consensus (HCCA), GFS or HWRF forecasts, and additional
eastward adjustments may be needed in subsequent forecasts.

The large convective burst this morning makes the short-term
intensity forecast somewhat tricky. If the low-level center is able
to reform and become better aligned with the mid-level center, some
intensification could occur. If and when this occurs is important,
with the latest HWRF and GFS forecasts suggesting this could occur
as soon as later today, resulting in more significant
intensification. However, the HMON, HAFS-S, and ECMWF suggest it may
take a few days for a more aligned structure to occur, likely
delayed by continued moderate (15-25 kts) southwesterly vertical
wind shear, which is expected to persist for the next 2-3 days. The
latest NHC intensity forecast opts to split the difference, now
showing gradual intensification over the next 24-48 hours, making
Earl a hurricane in 48 hours. This is higher than the previous NHC
intensity forecast, but is under the latest HCCA, HWRF, and
GFS-SHIPS guidance. After 72 h, shear is expected to decrease, and
more robust intensification is possible thereafter, with the latest
intensity forecast now making Earl a major hurricane by 120 h, in
good agreement with the IVCN and HCCA consensus aids.

At this juncture, 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 tonight.


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 today.  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 today, but gusty winds, especially in squalls,
remain possible on those islands.


FORECAST POSITIONS AND MAX WINDS

INIT  04/1500Z 19.5N  64.4W   45 KT  50 MPH
 12H  05/0000Z 20.4N  65.0W   50 KT  60 MPH
 24H  05/1200Z 21.5N  65.2W   55 KT  65 MPH
 36H  06/0000Z 22.6N  65.4W   60 KT  70 MPH
 48H  06/1200Z 23.5N  65.5W   65 KT  75 MPH
 60H  07/0000Z 24.7N  65.4W   70 KT  80 MPH
 72H  07/1200Z 25.7N  65.0W   75 KT  85 MPH
 96H  08/1200Z 27.2N  64.0W   85 KT 100 MPH
120H  09/1200Z 29.6N  61.8W  100 KT 115 MPH

$$
Forecaster Papin
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