Official Discussion issued by the National Hurricane Center

Ernesto (AL052024) DATA RELEASED: 8/18/2024 9:00:00 AM UTC

Copy of official data

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