[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 062100
TCDAT1

Tropical Storm Earl Discussion Number  16
NWS National Hurricane Center Miami FL       AL062022
500 PM AST Tue Sep 06 2022

Earl has become somewhat better organized this afternoon. After the
previous reconnaissance mission concluded, deep convection increased
closer to the low-level circulation, with evidence of deep
convection rotating more up-shear on convectional satellite imagery.
An AMSR2 microwave pass at 1728 UTC also showed this improved
structure, with a formative inner core with at least 50 percent
convective coverage, though it was still evident that the mid-level
center remains displaced to the northeast. This afternoon's Air
Force Reserve Reconnaissance mission confirmed Earl has strengthened
from this morning, with peak 850 mb flight level winds of 72 kt and
SFMR at 63 kt. The second pass through also had a minimum pressure
of 991 mb. These values support increasing the initial intensity to
60 kt this advisory.

Aircraft fixes indicate that Earl has resumed a northward motion,
with the latest estimate at 355/6 kt. There is not much change in
the track reasoning this cycle, as the mid-level ridge over Earl is
expected to break down further and a positively-tilted deep-layer
trough moves offshore of the eastern United States. This trough is
expected to capture the tropical cyclone, helping Earl to recurve to
the northeast with a faster forward motion after 36 hours. The track
guidance did shift a bit to the west this cycle and the latest NHC
track forecast is also bit west of the previous cycle, closest to
the HCCA consensus aid, which remains slightly east of the latest
GFS Forecast.

Earl seems to be effectively battling some rather hostile westerly
deep-layer (200-850 mb) vertical wind shear, estimated at 25-30 kt
in the GFS and ECMWF-based SHIPS. Earl's resiliency is possibly
related to the shear under this deep-layer being lower in magnitude
and Earl's vortex column not extending all the way to 200 mb. Given
the improvement in structure today, the latest intensity forecast
now shows some slow intensification despite the shear in the next
12-24 hours. After this period, the shear is forecast to rapidly
decrease to under 10 kt by 48 hours, as the cyclone continues to
traverse anomalously warm 29-30 C sea-surface temperatures. The
majority of the models respond to this favorable environment by
showing significant deepening. The latest NHC intensity forecast is
a bit higher than the prior one, now showing a peak of 110 kt in 72
hours, similar to the latest HCCA guidance. Thereafter, Earl will
likely begin the process of extratropical transition as it interacts
with a mid-latitude trough, with this transition likely to complete
sometime between the 4-5 day time frame when all deep convection is
stripped away.

Earl's center is expected to pass to the southeast of Bermuda in
48-60 hours. However, the size of the wind field of the tropical
cyclone is expected to increase significantly, and the Bermuda
Weather Service has issued a tropical storm watch for the Island of
Bermuda.


FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 24.1N  65.8W   60 KT  70 MPH
 12H  07/0600Z 25.0N  65.7W   65 KT  75 MPH
 24H  07/1800Z 26.3N  65.6W   70 KT  80 MPH
 36H  08/0600Z 27.9N  65.2W   80 KT  90 MPH
 48H  08/1800Z 29.9N  64.5W   90 KT 105 MPH
 60H  09/0600Z 31.9N  62.7W  100 KT 115 MPH
 72H  09/1800Z 35.0N  59.1W  110 KT 125 MPH
 96H  10/1800Z 42.0N  50.0W   90 KT 105 MPH
120H  11/1800Z 45.0N  41.5W   60 KT  70 MPH...POST-TROP/EXTRATROP

$$
Forecaster Papin
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