Tropical Depression Eighteen Advisory Number 1
NWS National Hurricane Center Miami FL AL182020
800 AM CVT Mon Sep 07 2020
...TROPICAL DEPRESSION FORMS OVER THE FAR EASTERN TROPICAL
ATLANTIC...
...EXPECTED TO BRING TROPICAL STORM CONDITIONS AND HEAVY
RAINFALL TO THE CABO VERDE ISLANDS...
SUMMARY OF 800 AM CVT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...15.2N 20.3W
ABOUT 250 MI...405 KM ESE OF THE CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES
WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:
The Government of the Cabo Verde Islands has issued a Tropical
Storm Warning for all of the Cabo Verde Islands.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Tropical Storm Warning is in effect for...
* Cabo Verde Islands
A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area, in this case within the
next 12 to 24 hours.
For storm information specific to your area, please monitor
products issued by your national meteorological service.
DISCUSSION AND OUTLOOK
----------------------
At 800 AM CVT (0900 UTC), the center of Tropical Depression Eighteen
was located near latitude 15.2 North, longitude 20.3 West. The
depression is moving toward the west near 12 mph (19 km/h), and
this general motion with some increase in forward speed is expected
over the next few days. On the forecast track, the center of the
cyclone is forecast to pass near or over the Cabo Verde Islands
later today and tonight.
Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Gradual strengthening is forecast during the next 48 hours, and the
depression is forecast to become a tropical storm later today or
tonight.
The estimated minimum central pressure is 1004 mb (29.65 inches).
HAZARDS AFFECTING LAND
----------------------
Key messages for the depression can be found in the Tropical
Cyclone Discussion under AWIPS header MIATCDAT3 and WMO header
WTNT43 KNHC.
RAINFALL: The tropical depression is expected to produce 2 to 5
inches of rain across portions of the Cabo Verde Islands through
Tuesday.
WIND: Tropical storm conditions are expected to begin over the
eastern portions of the Cabo Verde Islands later today and spread
westward across the remainder of those islands tonight.
NEXT ADVISORY
-------------
Next intermediate advisory at 1100 AM CVT.
Next complete advisory at 200 PM CVT.
$$
Forecaster Brown
Tropical Depression Eighteen Discussion Number 1
NWS National Hurricane Center Miami FL AL182020
800 AM CVT Mon Sep 07 2020
Shower and thunderstorm activity associated with the area of low
pressure over the far eastern Atlantic has continued to increase
and become organized in a band overnight. First light visible
satellite imagery suggests that the circulation has also become
better defined. Based on the above, advisories are being initiated
on a new tropical depression, the eighteenth of the 2020 Atlantic
hurricane seasons. Dvorak satellite estimates from both TAFB and
SAB support an intensity of 25 kt, but given the continued
improvement in organization the initial winds are set at 30 kt for
this advisory. ASCAT data later this morning should provide
additional information on the intensity of the cyclone.
The depression lies within a favorable upper-level environment and
the SHIPS guidance indicates that the vertical wind shear will
remain 10 kt or less over the next few days while the depression
traverses sea surface temperatures of around 27 degrees Celsius.
These conditions, along with a moist mid-level atmosphere should
allow for steady strengthening over the next few days, and the NHC
forecast calls for the system to become a tropical storm later
today, and a hurricane in about 72 hours. After that time, the
cyclone is forecast to pass over slightly cooler waters and the
global models depict an increase in southwesterly upper-level flow
over the system by the end of the period. These less conducive
factors are expected to slow the intensification process toward the
end of the period. The NHC intensity forecast is a blend of the
IVCN multi-model consensus and the HFIP corrected consensus.
The initial motion of the depression is a somewhat uncertain 280/10
kt. A narrow mid-level ridge to the north of the depression is
forecast to build westward over the next few days which is expected
to steer the system westward to west-northwestward, and the track
guidance is in good agreement through 72 hours. After that time, a
weakness is forecast to develop in the ridge near 40 degrees west.
and the cyclone is expected to turn west-northwestward and then
northwestward between the ridge to its northeast and Tropical
Depression Seventeen to its southwest. Since there could be some
binary interaction between the two tropical cyclones later in the
period, the longer range track guidance is not in as good of
agreement, and there is more uncertainty than average in the
long-range track forecast.
Key Messages:
1. The depression is forecast to strengthen into a tropical storm
later today and tropical storm conditions are expected to spread
over portions of the Cabo Verde Islands later today and tonight. A
Tropical Storm Warning is in effect for those islands.
2. The depression is expected to bring locally heavy rainfall to
portions of the Cabo Verde Islands through Tuesday morning.
FORECAST POSITIONS AND MAX WINDS
INIT 07/0900Z 15.2N 20.3W 30 KT 35 MPH
12H 07/1800Z 15.6N 22.0W 35 KT 40 MPH
24H 08/0600Z 16.0N 24.5W 40 KT 45 MPH
36H 08/1800Z 16.4N 27.3W 50 KT 60 MPH
48H 09/0600Z 16.8N 30.2W 55 KT 65 MPH
60H 09/1800Z 17.4N 32.9W 60 KT 70 MPH
72H 10/0600Z 18.1N 35.5W 65 KT 75 MPH
96H 11/0600Z 19.7N 39.6W 70 KT 80 MPH
120H 12/0600Z 22.4N 43.2W 70 KT 80 MPH
$$
Forecaster Brown