Tropical Report

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Sun Sep 23 2018

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on weakening
Tropical Depression Eleven, located several hundred miles east of
the Windward Islands, and on Tropical Storm Kirk, located several
hundred miles south-southwest of the Cabo Verde Islands.

1. A broad area of low pressure located between Bermuda and the Bahamas
continues to produce limited shower and thunderstorm activity.
The strong upper-level winds currently affecting the system are
expected to diminish, and this could favor some development during
the next couple of days. The low is forecast to move westward and
west-northwestward at about 10 mph over the southwestern Atlantic
Ocean and by Tuesday or Wednesday, upper-level winds are forecast
to strengthen again, likely limiting the development. By then,
the system is expected to be moving by the southeastern coast of
the United States.
* Formation chance through 48 hours…low…20 percent.
* Formation chance through 5 days…low…30 percent.

2. The evolution of a complex weather system over the central Atlantic
Ocean could lead to two separate episodes of subtropical or
tropical development during the upcoming week. First, a non-
tropical low pressure system currently located about 1000 miles
west-southwest of the Azores is producing gale-force winds with
some associated showers and thunderstorms. Conditions appear
conducive for this system to acquire some subtropical or tropical
characteristics during the next day or so while meandering over the
central Atlantic Ocean, and the low could become a subtropical or
tropical cyclone before it is overtaken and absorbed by a cold front
late Tuesday or Wednesday. Additional information on this system
can be found in High Seas Forecasts issued by the National Weather
Service.
* Formation chance through 48 hours…high…70 percent.
* Formation chance through 5 days…high…70 percent.

3. A second non-tropical low pressure system is expected to form
along the central Atlantic cold front by Wednesday several hundred
miles west of the Azores. Conditions appear conducive for this
system to also acquire subtropical or tropical characteristics by
the latter part of this week.
* Formation chance through 48 hours…low…near 0 percent.
* Formation chance through 5 days…low…30 percent.

Public Advisories on Kirk are issued under WMO header WTNT32 KNHC
and under AWIPS header MIATCPAT2. Forecast/Advisories on Kirk are
issued under WMO header WTNT22 KNHC and under AWIPS header
MIATCMAT2.

High Seas Forecasts issued by the National Weather Service can be
found under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and
on the Web at https://ocean.weather.gov/shtml/NFDHSFAT1.shtml.

Forecaster Avila

KIRK ACCELERATING WESTWARD OVER THE EASTERN TROPICAL ATLANTIC

Tropical Storm Kirk Discussion Number 5
NWS National Hurricane Center Miami FL AL122018
1100 AM AST Sun Sep 23 2018

Kirk’s cloud pattern has a figure 6 configuration, with most of the
deep convective bands over the western semicircle of the
circulation. Microwave imagery indicates that the center is near
the eastern side of the main area of deep convection, as before.
Dvorak classifications from both TAFB and SAB support keeping the
intensity at 35 kt. The storm will be moving over warmer waters
with fairly low shear for the next day or two, so some strengthening
is anticipated in the short term. Later in the forecast period,
increasing westerly shear should cause weakening. The official
intensity forecast is similar to the model consensus through 48
hours, and follows the trends shown by the ECMWF and GFS global
guidance thereafter. The latter models suggest that Kirk could open
up into a trough when it nears the Caribbean.

Center fixes indicate that Kirk has been accelerating westward and
the initial motion estimate is now 280/18 kt. A well-defined
mid-level ridge to the north of the cyclone should cause an even
faster westward motion over the next few days. Near the end of the
forecast period, a weakness in the ridge is likely to lead to a
slowing of the forward speed. The official forecast is a blend of
the latest simple and corrected model consensus forecast tracks and
is also similar to the previous NHC track.

FORECAST POSITIONS AND MAX WINDS

INIT 23/1500Z 9.3N 30.2W 35 KT 40 MPH
12H 24/0000Z 9.8N 33.2W 40 KT 45 MPH
24H 24/1200Z 10.2N 37.3W 45 KT 50 MPH
36H 25/0000Z 10.5N 41.5W 50 KT 60 MPH
48H 25/1200Z 10.7N 45.6W 50 KT 60 MPH
72H 26/1200Z 11.2N 52.4W 45 KT 50 MPH
96H 27/1200Z 12.3N 57.5W 40 KT 45 MPH
120H 28/1200Z 13.5N 62.0W 35 KT 40 MPH

Remnants of Eleven Forecast Discussion