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Tropical Storm Zeta Discussion Number   7
NWS National Hurricane Center Miami FL       AL282020
500 AM EDT Mon Oct 26 2020
 
Zeta's satellite presentation has continued to improve overnight. 
The cold convective cloud shield has expanded northwestward over the 
center and there has been a continued increase in banding over the 
southern and southeastern portions of the circulation. With the 
expansion of the convection over the center, it appears that a CDO 
feature is trying to form. A NOAA P-3 reconnaissance aircraft that 
has been investigating Zeta overnight has reported that the pressure 
has fallen to 990 mb.  The aircraft has found peak 850-mb 
flight-level winds of 69 kt and believable SFMR winds of around 60 
kt, with some higher flagged values.  These data support increasing 
the initial intensity to 60 kt for this advisory.
 
Recent aircraft fixes indicate that Zeta has begun its expected 
northwestward motion at about 315 degrees at 8 kt.  The storm should 
begin to move at an even faster pace toward the northwest as a 
mid-level ridge builds over the western Atlantic and Florida during 
the next 24 to 36 hours. This ridge will steer Zeta across the 
northern portion of the Yucatan peninsula tonight, and over the 
south-central Gulf of Mexico on Tuesday.  A vigorous mid- to 
upper-level trough currently over the western United States is 
forecast to begin ejecting out of the southwestern U.S. by mid-week, 
which will erode the western portion of the aforementioned ridge.  
This should cause Zeta to accelerate northward and approach the 
northern Gulf of Mexico on Wednesday.  The 0000 UTC global models, 
which incorporated dropwindsonde data from the earlier NOAA G-IV 
synoptic surveillance mission, have come into somewhat better 
agreement this cycle.  While there is still some spread on exactly 
when the northward turn takes place and how quickly Zeta accelerates 
north-northeastward over the Gulf of Mexico, the cross-track spread 
at 60 h is about half of what it was before, resulting in an 
increase in track-forecast confidence.  The latest NHC track is in 
best agreement with the GFS ensemble mean and the GFEX consensus 
aid.  This is a little right of the TVCA and HCCA multi-model 
consensus, but quite close to the previous NHC track forecast.
 
With the recent improvement in the outflow over Zeta, it appears 
that the shear that had prevented strengthening has abated.  The 
shear ahead of the storm is expected to remain low while the cyclone 
traverses the deep, warm water of the northwestern Caribbean Sea. 
As a result, Zeta is forecast to become a hurricane this morning, 
and continued strengthening is likely until Zeta moves over the 
Yucatan peninsula this evening. The landfall intensity is likely to 
be a little stronger than shown below since Zeta will be inland over 
the Yucatan peninsula by the 24-hour forecast point.  Environmental 
conditions over the southern Gulf of Mexico are forecast to be 
conducive for some re-strengthening as Zeta moves over the 
south-central Gulf on Tuesday.  Increasing shear and the cooler 
shelf waters of the northern Gulf are likely to result in some 
reduction in intensity before Zeta reaches the northern Gulf coast. 

KEY MESSAGES:
 
1. Hurricane conditions and storm surge are expected in portions of
the northern Yucatan Peninsula of Mexico tonight and early Tuesday.
Tropical storm conditions could occur over extreme western Cuba
beginning later today.
 
2. Through Tuesday, heavy rainfall is expected from Zeta across the 
Yucatan Peninsula of Mexico, the Cayman Islands, and central to 
western Cuba. This rainfall may 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  26/0900Z 18.7N  84.3W   60 KT  70 MPH
 12H  26/1800Z 19.5N  85.5W   75 KT  85 MPH
 24H  27/0600Z 20.8N  87.5W   75 KT  85 MPH...INLAND
 36H  27/1800Z 22.5N  89.6W   65 KT  75 MPH...OVER WATER
 48H  28/0600Z 24.7N  91.1W   70 KT  80 MPH
 60H  28/1800Z 27.7N  90.8W   65 KT  75 MPH
 72H  29/0600Z 31.8N  88.2W   45 KT  50 MPH...INLAND
 96H  30/0600Z 39.0N  75.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  31/0600Z...DISSIPATED
 
$$
Forecaster Brown
 
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