NHC issues Tropical Cyclone Discussion (TCD) at Aug 18, 1:00 PM AST082
WTNT45 KNHC 180846
TCDAT5
Tropical Storm Ernesto Discussion Number 27
NWS National Hurricane Center Miami FL AL052024
500 AM AST Sun Aug 18 2024
Ernesto's cloud pattern hasn't changed much overnight, and lacks a
well-defined eye feature. Deep convection has been trying to
wrap around the eastern portion of the circulation, giving the
system a fairly symmetric overall appearance. The current
intensity estimate is held at 60 kt which is in good agreement with
the latest objective, AID, estimates from UW-CIMSS. Subjective
Dvorak satellite estimates are somewhat lower. Unfortunately the
most recent scatterometer overpasses missed most of the circulation.
The tropical cyclone continues on a rather slow north-northeastward
heading, with an initial motion estimate of 025/8 kt. The steering
flow on the east side of a large mid-tropospheric trough approaching
the U.S. east coast should cause an increase in forward speed during
the next day or so along with a turn toward the northeast. In 2-3
days, Ernesto is likely to turn toward the east-northeast with
additional acceleration as it becomes embedded in the mid-latitude
westerlies over the north Atlantic. The track guidance models
remain in good agreement, and little changes to the previous NHC
track forecast were required.
Ernesto is still over warm waters, and should remain over SSTs of
at least 27 deg C for the next 24 hours or so. Also, vertical wind
shear is forecast to remain low today with upper-level divergence
diagnosed over the area by the SHIPS model diagnostics. These
environmental factors favor a short period of restrengthening
today, and this reflected in the official forecast. In 36-48
hours, the cyclone will encounter much cooler waters and this
should cause weakening. Simulated IR satellite imagery from the
global models show an increasingly asymmetric cloud structure by
the time the system passes near Newfoundland, and the official
forecast indicates post-tropical transition by 48 hours. Ernesto
is predicted to open up and become a large trough over the
northeastern Atlantic by 96 hours.
Key Messages:
1. Even though Ernesto is forecast to remain well offshore of the
U.S. East Coast, swells generated by the hurricane are expected to
affect the area through early next week. Beach goers should be
aware that there is a significant risk of life-threatening surf and
rip currents, and should stay out of the water if advised by
lifeguards. Surf and rip currents are also possible on the Bahamas,
Bermuda, and Atlantic Canada during the next few days.
2. Ernesto could bring wind, wave and wave impacts to portions of
southeastern Newfoundland late Monday and Monday night.
FORECAST POSITIONS AND MAX WINDS
INIT 18/0900Z 34.6N 63.0W 60 KT 70 MPH
12H 18/1800Z 36.4N 62.2W 65 KT 75 MPH
24H 19/0600Z 39.4N 60.4W 70 KT 80 MPH
36H 19/1800Z 42.9N 56.5W 65 KT 75 MPH
48H 20/0600Z 46.4N 50.3W 55 KT 65 MPH...POST-TROPICAL
60H 20/1800Z 49.0N 41.4W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 21/0600Z 51.0N 31.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 22/0600Z...DISSIPATED
$$
Forecaster Pasch
Source:
NHC issues Tropical Cyclone Discussion (TCD) at Aug 18, 1:00 PM AST---------------
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