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老農民版夜神月|2020-11-1 05:00
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本帖最後由 老農民版夜神月 於 2020-11-1 05:03 編輯
NHC21Z升格29L,首報上望75節000
WTNT44 KNHC 312050
TCDAT4
Tropical Depression Twenty-Nine Discussion Number 1
NWS National Hurricane Center Miami FL AL292020
500 PM EDT Sat Oct 31 2020
Showers and thunderstorms have continued to become better organized
in association with a tropical wave which has been moving westward
across the central Caribbean Sea. It was unclear this morning if
the system had developed a closed low-level circulation, since
scatterometers have avoided the system over the past 24 hours, but
recent visible and microwave satellite images suggest that the
system almost certainly now has a well-defined center. For that
reason, the system is being designated as a tropical depression with
30-kt winds, based on Dvorak classifications of T2.0 from both TAFB
and SAB.
A low- to mid-level ridge axis that extends from the subtropical
Atlantic southwestward to Cuba and the Bahamas is currently steering
the depression toward the west (270 degrees) at an estimated speed
of 13 kt. Model guidance is in fairly good agreement on the
depression's future track for the first 48 hours or so. The cyclone
is expected to continue westward for the first 36 hours and then
slow down and turn west-southwestward by 48 hours as it approaches
the coasts of Nicaragua and Honduras, in response to a building
ridge over the Gulf of Mexico. After that time, however, there is
significant divergence in the models. For example, the ECWMF and
its ensemble members continue on a faster westward motion across
Central America, while the GFS and its ensemble members stall the
system over the western Caribbean Sea through day 5. Given this
discrepancy, the NHC official track forecast shows a slow motion on
days 3 through 5, and brings the cyclone's center slowly across
northern Nicaragua, more or less in line with the multi-model
consensus aids. This forecast is of generally low confidence,
however, and significant changes could be required in later advisory
packages depending on model trends.
The waters over the Caribbean Sea remain very warm--around 29
degrees Celsius--and the environment is characterized by low
vertical shear of 10 kt or less. Along with plenty of ambient
moisture, these parameters suggest the system is primed for steady,
if not significant, strengthening during the next few days. The NHC
official forecast generally lies between the SHIPS guidance and the
HCCA corrected-consensus aid, which lie near the upper bound of the
intensity guidance, and it brings the system to hurricane strength
in 48 hours. The intensity forecast hinges greatly on whether or
not the cyclone's center moves inland over Central America, but
regardless, the system is expected to be a hurricane when it
approaches the Honduras and Nicaragua coasts in a few days.
Key Messages:
1. The depression is expected to strengthen to a hurricane early
next week as it approaches the coast of Central America late Monday
and Monday night, and there is a risk of storm surge,
hurricane-force winds, and heavy rainfall for portions of Nicaragua
and Honduras. Hurricane Watches could be needed for portions of
those areas later tonight.
2. Through Thursday afternoon, heavy rainfall from the system will
likely lead to flash flooding and river flooding across portions of
Jamaica, the Cayman Islands, and Central America, which could result
in landslides in areas of higher terrain. Flooding is also possible
near the southern coast of Hispaniola.
FORECAST POSITIONS AND MAX WINDS
INIT 31/2100Z 15.0N 73.2W 30 KT 35 MPH
12H 01/0600Z 15.1N 75.6W 35 KT 40 MPH
24H 01/1800Z 15.4N 78.3W 45 KT 50 MPH
36H 02/0600Z 15.5N 80.4W 55 KT 65 MPH
48H 02/1800Z 15.1N 82.1W 65 KT 75 MPH
60H 03/0600Z 14.3N 83.1W 75 KT 85 MPH
72H 03/1800Z 13.8N 83.7W 70 KT 80 MPH...INLAND
96H 04/1800Z 13.5N 85.5W 40 KT 45 MPH...INLAND
120H 05/1800Z 14.0N 86.9W 25 KT 30 MPH...INLAND
$$
Forecaster Berg
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