[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 131806
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
205 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 1200 UTC surface analysis and satellite imagery through
1715 UTC.

...SPECIAL FEATURES...

The center of Hurricane Florence at 13/1800 UTC is near 33.6N
76.0W. Florence is moving NW, or 315 degrees, at 9 knots. This
position is about 95 nm ESE of Wilmington in North Carolina, and
about 145 nm E of Myrtle Beach in South Carolina. The estimated
minimum central pressure is 955 mb. The maximum sustained wind
speeds are 90 knots with gusts to 110 knots. Scattered moderate to
strong convection is from 31N-37N between 72W-79W. The present NW
motion is forecast to continue through today, with a decrease in
forward speed. A turn to the west-northwest and west at an even
slower forward speed is expected Thursday night and Friday, and a
slow west-southwestward motion is forecast Friday night and
Saturday. On the forecast track, the center of Florence will
approach the coasts of North and South Carolina later today, then
move near or over the coast of southern North Carolina and
northeastern South Carolina in the hurricane warning area tonight
and Friday. A slow motion over eastern South Carolina is forecast
Friday night through Saturday night. Little change in strength is
expected before the center reaches the coast, with weakening
expected after the center moves inland. 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 centered near 14.9N 62.5W at 13/1800 UTC or
70 nm WSW of Dominica moving W at 16 kt. The estimated minimum
central pressure is 1006 mb. The maximum sustained wind speeds are
40 knots with gusts to 50 knots. Scattered moderate convection is
from 12N-17N between 56W-63W. A westward motion with a decrease
in forward speed is expected to continue through the next few
days. On the forecast track, Isaac is forecast to move farther
away from the Lesser Antilles today, and then move across the
eastern and central Caribbean Sea through the weekend. 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 24.8N 37.3W at 13/1500 UTC
or 985 nm SW of Lajes Air Base In The Azores moving N at 12 kt.
The estimated minimum central pressure is 989 mb. The maximum
sustained wind speeds are 60 knots with gusts to 75 knots.
Scattered moderate/isolated strong convection is from 25N-29N
between 36W-40W. The system should accelerate and turn toward the
northeast by Sunday. Continued weakening is forecast over the
next couple of days. 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.

The center of Subtropical Storm Joyce at 13/1500 UTC is near
33.7N 43.7W. The estimated minimum central pressure is 1006 mb.
The maximum sustained wind speeds are 35 knots with gusts to 45
knots. Isolated moderate convection is from 32N-36N between 40W-
44W. A turn toward the south-southwest and then toward the south
is expected later today through early Friday. A graudal 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 21N-27N between 91W-97W. While upper-level winds are
conducive for development of a tropical depression, the system has
only about a day before it reaches the western Gulf coast. An Air
Force Reserve Hurricane Hunter aircraft is currently en route to
investigate the low. Heavy rainfall and gusty winds are expected
across parts of northeastern Mexico and Texas on Friday and
Saturday. Please monitor the progress of this system, and refer to
bulletins and forecasts from your local weather office. This
system has a medium chance of tropical cyclone development before
it moves inland on Friday. 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 22W, from 06N-24N. The wave is supported
by well pronounced 700 mb troughing as depicted in the GFS model
guidance. Scattered weak/isolated moderate convection is between
04N-10N between 17W-28W.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from W Africa near 17N16W to 08N24W to
10N41W. The ITCZ continues from 10N41W to 10N49W to 13N55W. Aside
from the convection associated with the tropical wave along 22W,
scattered weak/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 28N83W. The Gulf east of 87W is free of any
significant convection at this time.

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
15N78W. 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

$$
Hagen/MT
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