Hurricane Ernesto Discussion Number  25
NWS National Hurricane Center Miami FL       AL052024
500 PM AST Sat Aug 17 2024

Recent infrared and microwave imagery indicate show that Ernesto's 
convective activity is a little thin, with the deepest convection 
located in a small band just north of the center.  Subjective and 
objective satellite intensity estimates have decreased through the 
day, and combined with the earlier data from the Hurricane Hunter 
aircraft--which only measured 700-mb wind of 74 kt--it is estimated 
that Ernesto's maximum sustained winds are near 65 kt.

Ernesto has slowed down during the day while moving away from 
Bermuda, and the initial motion is north-northeastward (030 
degrees) at 5 kt.  This slow motion is likely to continue for the 
next 12 hours or so, before the flow increases ahead of an 
approaching trough and causes Ernesto to accelerate toward the 
north-northeast on Sunday.  The cyclone is forecast to turn 
northeastward on Monday, and model guidance continues to show the 
center passing just to the southeast of Newfoundland late Monday or 
Monday night.  After passing Newfoundland, Ernesto is expected to 
accelerate further toward the east-northeast over the north 
Atlantic.  The track guidance is very tightly packed through 72 
hours, and no significant changes were required from the previous 
NHC forecast.

Despite Ernesto's recent weakening, the hurricane will move over 
warm waters of 28 degrees Celsius and within a light-shear 
environment for the next 24 hours or so.  The storm's current broad 
structure may not allow for significant strengthening within this 
otherwise favorable environment, but many of the dynamical 
hurricane models, global models, and consensus aids suggest that 
Ernesto could re-intensity by 5-10 kt over the next day or so.  
This is reflected in the official intensity forecast.  Weakening 
should begin by 48 hours due increasing shear and Ernesto moving 
over colder waters north of the Gulf Stream, and the cyclone is 
likely to become post-tropical by 60 hours while it is passing near 
southeastern Newfoundland.  The GFS and ECMWF models indicate that 
dissipation should occur by day 4 when the circulation opens up 
into a trough over the north Atlantic.


Key Messages:

1. Ernesto is moving slowly, and its impacts on Bermuda are
not over.  Strong winds, heavy rainfall, coastal flooding, and
battering waves should continue through tonight.  The heavy rains 
will likely result in considerable life-threatening flash flooding,
especially in low-lying areas on the island.

2. 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 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.

3. Ernesto could bring wind, wave, and rain impacts to portions of
southeastern Newfoundland late Monday and Monday night.


FORECAST POSITIONS AND MAX WINDS

INIT  17/2100Z 33.3N  64.0W   65 KT  75 MPH
12H  18/0600Z 34.3N  63.6W   65 KT  75 MPH
24H  18/1800Z 36.5N  62.6W   70 KT  80 MPH
36H  19/0600Z 39.5N  60.9W   70 KT  80 MPH
48H  19/1800Z 43.0N  57.2W   65 KT  75 MPH
60H  20/0600Z 46.4N  50.9W   55 KT  65 MPH...POST-TROP/EXTRATROP
72H  20/1800Z 48.9N  42.1W   45 KT  50 MPH...POST-TROP/EXTRATROP
96H  21/1800Z...DISSIPATED

$$
Forecaster Berg