[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 140000
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
800 PM EDT Thu Sep 13 2018

Tropical Weather Discussion for North America, Central America
Gulf of Mexico, Caribbean Sea, northern sections of South
America, and Atlantic Ocean to the African coast from the
Equator to 32N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 1800 UTC surface analysis and satellite imagery through
2315 UTC.

...SPECIAL FEATURES...

Hurricane Florence is centered near 33.7N 76.2W at 13/2100 UTC or
90 nm ESE of Wilmington North Carolina moving WNW at 4 kt.
Estimated minimum central pressure is 955 mb. Maximum sustained
wind speed is 85 kt with gusts to 105 kt. Scattered moderate to
strong convection is from 32N-37N between 72W-80W. The present
WNW motion is forecast to continue into Friday. A slow westward to
west- southwestward motion is expected Friday night and Saturday.
On the forecast track, the center of Florence will approach the
coasts of North and South Carolina later tonight, then move near
or over the coast of southern North Carolina and northeastern
South Carolina in the hurricane warning area on Friday. A slow
motion across portions of eastern and central South Carolina is
forecast Friday night through Saturday night. The combination of
a dangerous storm surge and the tide will cause normally dry areas
near the coast to be flooded by rising waters moving inland from
the shoreline. Public Advisories for Florence are issued under
WMO header WTNT31 KNHC and under AWIPS header MIATCPAT1. Forecast/
Advisories for Florence are issued under WMO header WTNT21 KNHC
and under AWIPS header MIATCMAT1.

Tropical Storm Isaac is centered near 14.9N 63.2W at 13/2100 UTC
or 190 nm SSE of St. Croix moving W at 14 kt. Estimated minimum
central pressure is 1006 mb. Maximum sustained wind speed is 35 kt
with gusts to 45 kt. Scattered moderate to isolated strong convection
is from 12N-16N between 55W-63W. A westward motion with a
decrease in forward speed is expected to continue through the next
few days. Isaac should move farther away from Lesser Antilles
today, and then move across the eastern and central Caribbean Sea
through the weekend. Isaac is forecast to gradually weaken over
the next few days, and could degenerate into a tropical wave
during that time. Public Advisories for Isaac are issued under
WMO header WTNT34 KNHC and under AWIPS header MIATCPAT4. Forecast/
Advisories for Isaac are issued under WMO header WTNT24 KNHC and
under AWIPS header MIATCMAT4.

Tropical Storm Helene is centered near 26.3N 37.0W at 13/2100 UTC
or 900 nm SW of Lajes Air Base In The Azores moving N at 18 kt.
Estimated minimum central pressure is 993 mb. Maximum sustained
wind speed is 55 kt with gusts to 65 kt. Scattered moderate/
isolated strong convection is from 26N-31N between 36W-39W. The
system is expected to accelerate and turn toward the northeast by
Monday. On this forecast track, Helene will be crossing over or
near the Azores late Saturday or Sunday. Public Advisories for
Helene are issued under WMO header WTNT33 KNHC and under AWIPS
header MIATCPAT3. Forecast/ Advisories for Helene are issued under
WMO header WTNT23 KNHC and under AWIPS header MIATCMAT3.

Subtropical Storm Joyce is centered near 33.6N 44.2W at 13/2100
UTC or 880 nm WSW of the Azores moving SW at 5 kt. Estimated
minimum central pressure is 1003 mb. Maximum sustained wind speed
is 35 kt with gusts to 45 kt. Isolated moderate convection is from
32N-37N between 39W-45W. A turn toward the south-southwest and
then toward the south is expected later today through early
Friday. A gradual turn toward the east-northeast and northeast
with an increase in forward speed is expected Saturday and Sunday.
Little change in strength is forecast during the next 48 hours.
Joyce could transition to a tropical storm in the next day or two.
See latest NHC forecast/advisory under AWIPS/WMO headers
MIATCPAT5/WTNT35 KNHC for more details.

A weak low pressure center has formed a couple of hundred miles
east-southeast of Brownsville, Texas. Showers and thunderstorms
have become more numerous today. Scattered moderate convection is
between 20N-30N between 90W-99W. An Air Force reconnaissance
plane investigating the disturbance in the western Gulf of Mexico
found a broad and elongated area of low pressure with a few
squalls. Upper-level winds are conducive for development, and a
tropical depression could still form before the system moves
inland along the western Gulf coast on Friday. Another Air Force
reconnaissance plane will investigate the system on Friday if
necessary. Regardless of development, heavy rainfall and gusty
winds are expected across portions of northeastern Mexico and
Texas on Friday and Saturday. Please read the latest Tropical
Weather Outlook under WMO header ABNT20 KNHC, and under the AWIPS
header MIATWOAT for more details.

...TROPICAL WAVES...

A tropical wave is along 23W, from 06N-24N, movingW at 10 kt. The
wave is supported by well pronounced 700 mb troughing as depicted
in the GFS model guidance. Scattered moderate convection is
between 04N-10N between 17W-28W.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from W Africa near 16N17W to 09N23W to
10N40W. The ITCZ continues from 10N40W to 10N50W to 14N56W. Aside
from the convection associated with the tropical wave along 23W,
scattered moderate convection is from 07N-10N between 38W-46W.

...DISCUSSION...

GULF OF MEXICO...

Please read the SPECIAL FEATURS section for details about an area
of disturbed weather that is in the western Gulf of Mexico. An
upper-level low over the Florida Peninsula has moved westward into
the NE Gulf near 29N83W. Widely scattered moderate convection is
over the far NE Gulf of Mexico and Florida.

A dissipating stationary front is located along the Texas and SW
Louisiana coasts with scattered showers and isolated moderate
thunderstorms north of 27N to the Gulf Coast between 88W-96W.

CARIBBEAN SEA...

Please read the SPECIAL FEATURES section for details about
Tropical Storm Isaac.

The eastern extent of the eastern Pacific monsoon trough passes
through Costa Rica and Panama along 10N. Scattered moderate
convection is within 120 nm S of the monsoon trough.

An large upper level low is in the western Caribbean Sea near
18N80W. Isolated weak convection is between 13N-20N between 78W-
83W.

An an upper level high is centered in the NE Caribbean Sea near
19N69W, producing a good amount of shear over T.S. Isaac.

ATLANTIC OCEAN...

Please read the SPECIAL FEATURES section, for details about
Hurricane Florence, Tropical Storm Helene, and Subtropical Storm
Joyce.

No other significant features are noted in the Atlantic other than
the features mentioned above.

For additional information please visit
http://www.hurricanes.gov/marine

$$
Formosa
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