Tropical Storm ETA (Text)

Tropical Storm Eta Discussion Number  33
NWS National Hurricane Center Miami FL       AL292020
1000 AM EST Sun Nov 08 2020
Eta remains a sheared tropical storm, although the low-level center
has become embedded a little farther into the convective cloud mass.
Cuban radar data from Camaguey indicate that Eta's center has moved
back over water and is now located just offshore the east-central
coast of Cuba. Radar imagery also indicates that a fairly
impressive band of deep convection wraps more than half way around
the center, especially in the western semicircle. Cirrus outflow
has expanded in the southern semicircle, and indication that the
shear may be decreasing somewhat. However, water vapor satellite
imagery still shows a fair amount of dry mid-/upper-level air
impinging on the cyclone from the southwest. The initial intensity
of 55 kt is based on a report of 850-mb flight-level winds of 70 kt
and reliable SFMR winds of 55-57 kt.
The initial motion estimate is now 355/10 kt. Eta is interacting
with a sharp mid-/upper-level, negatively tilted trough that
extends east-southeastward across the Gulf of Mexico and into the
northwestern Caribbean Sea. The eastern end of the trough is
forecast to develop into a cutoff low alter today, which will act
to turn Eta northwestward by this afternoon, and westward later
tonight. The complex interaction between these two features is
forecast to continue through 72 hours, resulting in the development
of weak steering currents and Eta slowing down and possibly
stalling near or just west of the Florida Keys by day 3.
Thereafter, the global and regional models show widely varying
solutions ranging from a motion toward the south or southwest
(UKMET) toward Yucatan, to slow northward (ECMWF) or northeastward
motion (GFS/HWRF) over the eastern Gulf of Mexico. The new NHC
track forecast lies to the north, or to the right, of the  12Z
interpolated models and consensus models (due to the interpolater
possibly having some problems handling the sharp westward turn that
Eta is forecast to make), and lies close to the previous advisory
track and a blend of the operational 00Z ECMWF, and 06Z GFS and
UKMET model tracks.
Now that Eta's center is back over water, gradual re-strengthening
is expected to begin later this afternoon. The global models are
forecasting to vertical wind shear to steadily decrease across the
center for the next next 48 hours as Eta moves north of the cutoff
low and into a col small region region between the low and an
upper-level trough moving eastward across northern Florida. The
GFS- and ECMWF-based SHIPS intensity guidance indicate that the
shear will decrease to less than 10 kt by 36 hours, but the shear
will likely decrease sooner since SHIPS model uses winds that extend
out 500 km (270 nmi) from the center, which are not always
representative of the wind flow near the center. With favorable
low-shear conditions and sea-surface temperatures warmer than 28 deg
C, the only hindering factor appears to be proximity to dry
mid-level air, which could get entrained into the inner core and
inhibit development of deep convection in that part of the cyclone.
For now, the new NHC intensity forecast remains similar to the
previous advisory, which is above the model guidance up to 36 hours
and a little below the guidance thereafter, and shows Eta at 65 kt
or Category 1 hurricane intensity in the 24-72 hour period. However,
it is certainly possibly that if dry air does not penetrate into
Eta's inner core later today, then the cyclone could become a
hurricane before it reaches the Florida Keys tonight. For this
reason, a Hurricane Warning has been issued for portions of the
Florida Keys.
Key Messages:
1. Heavy rainfall from Eta will continue across portions of Cuba,
Jamaica, the Bahamas, and southern Florida and spread north into
central Florida. This rain may result in significant,
life-threatening flash flooding and river flooding in Cuba. Flash
and urban flooding will also be possible for Jamaica, the Bahamas
and southern Florida, along with potential minor river flooding in
central Florida.
2. Tropical storm conditions are expected to continue today in
portions of Cuba and the northwestern Bahamas, where Tropical Storm
Warnings are in effect.
3. Hurricane conditions are expected in portions of the Florida 
Keys by early Monday where a Hurricane Warning is now in effect.  
Damaging tropical-storm-force winds are expected to begin in the 
Florida Keys by this afternoon. Tropical Storm conditions are also 
expected and hurricane conditions are possible for portions of the 
southern Florida peninsula where a Tropical Storm Warning and 
Hurricane Watch are in effect. Elsewhere across portions of the east 
and west coasts of the Florida peninsula, the risk of 
tropical-storm-force winds will extend well away from Eta's center, 
and Tropical Storm Watches and Warnings are in effect.
4. A dangerous storm surge is expected in portions of the Florida 
Keys where a Storm Surge Warning is in effect. A Storm Surge 
Watch is also in effect for portions of the southern coast of 
the Florida peninsula.  Residents in the Storm Surge Warning 
and Watch areas should follow any advice given by local officials.
INIT  08/1500Z 22.5N  79.2W   55 KT  65 MPH
 12H  09/0000Z 24.1N  79.8W   60 KT  70 MPH
 24H  09/1200Z 24.5N  82.4W   65 KT  75 MPH
 36H  10/0000Z 23.9N  84.1W   65 KT  75 MPH
 48H  10/1200Z 23.8N  85.0W   65 KT  75 MPH
 60H  11/0000Z 24.0N  85.5W   65 KT  75 MPH
 72H  11/1200Z 24.9N  85.2W   65 KT  75 MPH
 96H  12/1200Z 26.2N  84.5W   55 KT  65 MPH
120H  13/1200Z 26.9N  83.9W   50 KT  60 MPH
Forecaster Stewart

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Page last modified: Thursday, 31-Dec-2020 12:10:45 UTC