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Tropical Storm Zeta Discussion Number   6
NWS National Hurricane Center Miami FL       AL282020
1100 PM EDT Sun Oct 25 2020
 
The tropical storm continues to produce deep convection on its south
side, with the low-level center estimated to be near the northern
edge of the thunderstorms.  The last pass from the NOAA Hurricane
Hunters a few hours ago indicated that the minimum pressure had
fallen to 997 mb, and since the storm appears better organized than
before the initial intensity is nudged up to 50 kt.  This intensity
estimate is slightly above the latest Dvorak numbers. The NOAA
Hurricane Hunters are planning to be in Zeta again overnight and
that data will be helpful in assessing the storm's intensity and
structure.
 
Zeta has not moved much during the past several hours, and the 
initial motion is a very slow north-northwest drift.  As ridging 
begins to build over and near Florida, Zeta is forecast to move 
faster to the northwest overnight and Monday, and that should take 
the center of the cyclone near or over the northeastern portion of 
the Yucatan Peninsula in about 24 hours.  The ridge is then expected 
to shift eastward over the western Atlantic on Tuesday and Wednesday 
as a large and quite powerful mid- to upper-level low moves eastward 
across the southwest and south-central United States.  This change 
in the steering pattern should cause Zeta to accelerate northward 
toward the northern Gulf Coast, and likely make landfall there on 
Wednesday.  The models remain in poor agreement on the details of 
the evolution of the steering pattern and consequently, there is 
about a 300 n mi spread in the landfall locations from the various 
models, which currently spans the region from the far western 
Florida panhandle to western Louisiana.  The NHC track forecast is a 
little west of the previous one trending toward the middle of the 
guidance envelope. Based on the poor model agreement, the confidence 
in the track forecast is lower than normal.  It is hoped that data 
being collected by the NOAA Gulfstream jet flying around Zeta 
and special NWS weather balloon launches will help the models come 
into better agreement on the future track of Zeta soon.
 
Given the low wind shear conditions, moist air mass, and high
oceanic heat content over the northwestern Caribbean, steady
strengthening seems likely until Zeta reaches the Yucatan Peninsula
by late Monday.  The cyclone is expected to be a hurricane at
landfall in Mexico, and the new forecast shows a slightly higher
intensity there based on the new models and favorable conditions.
The models differ on how long the core of Zeta will be inland over
the Yucatan, but in general, it seems likely that significant
weakening won't occur given the storm's expected increasing forward
speed.  The overall environmental conditions are anticipated to
remain generally favorable while Zeta moves across the southern Gulf
of Mexico, but there should be an increase in shear when it reaches
the central Gulf and the cyclone will then be moving over the
cooler shelf waters over the northern Gulf.  The combination of the
stronger shear and cooler waters should cause Zeta to level off
in strength and perhaps weaken slightly before the U.S. landfall.
The intensity models are in fair agreement, and the NHC forecast
lies near the HCCA and IVCN consensus models.
 
KEY MESSAGES:
 
1. Hurricane conditions and storm surge are expected in portions of
the northern Yucatan Peninsula of Mexico Monday night and early
Tuesday. Tropical storm conditions could occur over extreme western
Cuba on Monday.
 
2. Through Wednesday, heavy rainfall is expected from Zeta across
portions of central and western Cuba, the Cayman Islands, Jamaica,
the northeast Yucatan peninsula of Mexico, southern Florida and the
Keys. This rainfall could lead to flash flooding in urban areas.
 
3. Zeta is forecast to be at or near hurricane strength when
it approaches the northern Gulf Coast on Wednesday, and there is an
increasing risk of storm surge, rainfall, and wind impacts from
Louisiana to the Florida Panhandle. Residents in these areas should
monitor the progress of Zeta and updates to the forecast.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  26/0300Z 18.1N  83.8W   50 KT  60 MPH
 12H  26/1200Z 18.9N  84.7W   60 KT  70 MPH
 24H  27/0000Z 20.2N  86.5W   75 KT  85 MPH
 36H  27/1200Z 21.8N  88.6W   65 KT  75 MPH
 48H  28/0000Z 24.0N  90.4W   65 KT  75 MPH
 60H  28/1200Z 27.1N  91.1W   65 KT  75 MPH
 72H  29/0000Z 31.1N  89.6W   50 KT  60 MPH...INLAND
 96H  30/0000Z 38.7N  78.8W   30 KT  35 MPH...POST-TROP/EXTRATROP
120H  31/0000Z...DISSIPATED
 
$$
Forecaster Cangialosi
 
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