Hurricane Ernesto Discussion Number  19
NWS National Hurricane Center Miami FL       AL052024
500 AM AST Fri Aug 16 2024

Ernesto's strengthening trend has seemingly halted overnight.  The 
cloud pattern near the center has become less organized, and the 
system appears to be struggling with dry air again with some eyewall 
erosion in the western semicircle.  Still, the convective banding 
in the eastern side where the previous aircraft mission found the 
peak winds remains deep and well-defined, suggesting that Ernesto 
hasn't lost much strength.  The initial wind speed is kept at 85 kt 
for this advisory, a bit above the latest satellite estimates, 
pending the upcoming Air Force Reserve Hurricane Hunter aircraft 
mission this morning.

The environment near Ernesto could support some strengthening today. 
However, the most noticeable change in the overnight intensity 
guidance aids is that almost all of them are showing more shear 
today than previously expected.  This shear, combined with the 
environmental dry air, has led to this cycle's intensity forecast 
values being a lot lower than 6 h ago.  Given current trends, the 
NHC prediction has been decreased from the last forecast, and is 
still on the high side of the guidance.  It is worth noting that 
despite the peak wind speed reductions, the forecast size is 
generally larger than the previous forecast, so the 
life-threatening hazards from Ernesto are unchanged. After the 
hurricane passes Bermuda, there could be a brief window for some 
re-intensification in lighter shear conditions plus favorable trough 
influences before Ernesto crosses into cool waters, and little 
change was made at longer range.

Ernesto continues moving north-northeastward at about 11 kt, steered
by the flow between a ridge over the central Atlantic and a
large-scale trough off the U.S. east coast.  This general motion is
expected to persist for the next day or two, bringing the hurricane
near or over Bermuda on Saturday.  The trough is forecast is lift
out over the weekend, causing Ernesto to slow down and turn a bit to
the north or north-northeast.  Another trough is expected to
approach the cyclone late in the weekend, and that feature should
cause Ernesto to accelerate to the northeast near or east of
Newfoundland early next week.  The NHC track forecast continues to
the trend of the previous one, nudged a touch to the east and a
little slower through its passage near Bermuda to come into better
agreement with the latest aids.


Key Messages:

1. Ernesto is expected to bring a prolonged period of strong winds
and storm surge on Bermuda starting this afternoon through Saturday
night. A hurricane warning is in effect for the island, and
preparations to protect life and property should be rushed to
completion.

2. Heavy rainfall associated with Ernesto is expected to impact
Bermuda through this weekend and will likely result in considerable
life-threatening flash flooding.

3. Even though Ernesto is forecast to remain well offshore the U.S.
East Coast, swells generated by the hurricane are expected to affect
the area through the weekend.  Beach goers should be aware of a
significant risk of life-threatening surf and rip currents, and stay
out of the water if advised by lifeguards.  Surf and rip currents
are also possible on the Turks and Caicos, the Bahamas, Bermuda,
and Atlantic Canada during the next few days.


FORECAST POSITIONS AND MAX WINDS

INIT  16/0900Z 28.1N  67.0W   85 KT 100 MPH
12H  16/1800Z 29.6N  66.2W   90 KT 105 MPH
24H  17/0600Z 31.5N  65.2W   85 KT 100 MPH
36H  17/1800Z 32.8N  64.8W   80 KT  90 MPH
48H  18/0600Z 34.2N  64.4W   75 KT  85 MPH
60H  18/1800Z 36.2N  63.6W   75 KT  85 MPH
72H  19/0600Z 39.4N  61.6W   80 KT  90 MPH
96H  20/0600Z 47.0N  51.0W   60 KT  70 MPH...POST-TROPICAL
120H  21/0600Z 52.5N  31.0W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Blake