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Tropical Storm Zeta Discussion Number 5
NWS National Hurricane Center Miami FL AL282020
500 PM EDT Sun Oct 25 2020
Although the overall cloud pattern of Zeta is still not very well
organized, with a lack of distinct banding features, it continues to
generate very intense deep convection mainly over the southeastern
portion of the circulation. Moreover, in spite of its ragged
appearance, the storm has strengthened today. Reports from a NOAA
Hurricane Hunter aircraft investigating the system this afternoon
indicate that, based on adjusted flight-level and SFMR-observed
surface winds, the intensity has increased to near 45 kt and the
central pressure has fallen to 999 mb. Since the storm will be
moving over the high oceanic heat content of the northwestern
Caribbean Sea and in a moist environment with low vertical shear
through Monday, strengthening is forecast and Zeta will likely
become a hurricane before it nears the Yucatan Peninsula in a day or
so. After Zeta moves into the Gulf of Mexico, southwesterly shear
is likely to increase and oceanic heat content below the cyclone
will diminish, especially when the system approaches the northern
Gulf coast on Wednesday. Therefore, no strengthening is forecast in
2-3 days and Zeta could be weakening by the time it reaches the
northern Gulf coast. However, the intensity forecast is still
subject to significant uncertainty.
The center has been meandering this afternoon, and apparently has
reformed nearer to the deep convection over the southeastern
quadrant. Since this is not considered representative of
larger-scale motion, the system is still considered to be
quasi-stationary at this time. However, the track guidance is in
agreement that Zeta will move northwestward over the next 1-2 days,
passing near or over the Yucatan Peninsula. Thereafter, the cyclone
is likely to turn north-northwestward to northward while it moves on
the western side of a mid-tropospheric anticyclone near Florida. A
turn toward the north-northeast is expected when Zeta nears the
northern Gulf coast, due to an approaching shortwave trough. The
track guidance has more than the usual amount of spread at the
72-hour time frame, with the ECMWF and the GFS predictions being
about 300 miles apart near the northern Gulf coast. The official
forecast track lies between these 2 solutions, and is similar to the
previous NHC track. However, given the inherent uncertainties, one
should not focus on the exact forecast track.
Based on the new intensity forecast, the government of Mexico has
issued a Hurricane Warning for a portion of the Yucatan peninsula.
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 may lead to flash flooding in urban areas.
3. Zeta is forecast to be at or just below 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 25/2100Z 17.7N 83.4W 45 KT 50 MPH
12H 26/0600Z 18.7N 84.3W 55 KT 65 MPH
24H 26/1800Z 19.7N 85.7W 65 KT 75 MPH
36H 27/0600Z 21.1N 87.6W 65 KT 75 MPH...INLAND
48H 27/1800Z 23.2N 89.6W 65 KT 75 MPH
60H 28/0600Z 25.7N 90.8W 65 KT 75 MPH
72H 28/1800Z 29.4N 90.3W 60 KT 70 MPH...INLAND
96H 29/1800Z 37.0N 83.0W 25 KT 30 MPH...INLAND
120H 30/1800Z...DISSIPATED
$$
Forecaster Pasch
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