[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 100005
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 PM EDT Sun Sep 9 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
2330 UTC.

...SPECIAL FEATURES...

The center of Hurricane Florence at 09/2100 UTC is near 24.4N
57.0W. Florence is moving W, or 270 degrees, 06 knots. The
estimated minimum central pressure is 975 mb. The maximum
sustained wind speeds are 75 knots with gusts to 90 knots.
Scattered moderate to strong rainshowers are within 30 nm of the
center everywhere. Numerous strong rainshowers are from 24N to
26N between 56W and 58W. Scattered moderate to isolated strong
rainshowers are elsewhere from 21N to 27N between 53W and 61W.
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.

The center of Tropical Storm Isaac at 09/2100 UTC is near 14.5N
40.3W. Isaac is moving W, or 275 degrees, 10 knots. The estimated
minimum central pressure is 997 mb. The maximum sustained wind
speeds are 60 knots with gusts to 75 knots. Numerous strong
rainshowers are from 14N to 15N between 40W and 42W. Scattered
moderate to isolated strong rainshowers are elsewhere from 12N to
16N between 40W and 44W. Public Advisories for Tropical Storm
Isaac are issued under WMO header WTNT34 KNHC and under AWIPS
header MIATCPAT4. Forecast/Advisories for Tropical Storm Isaac are
issued under WMO header WTNT24 KNHC and under AWIPS header
MIATCMAT4.

The center of Hurricane Helene at 09/2100 UTC is near 13.4N
26.0W. HELENE is moving W, or 280 degrees, 11 knots. The estimated
minimum central pressure is 992 mb. The maximum sustained wind
speeds are 65 knots with gusts to 80 kt. Scattered moderate to
strong rainshowers are from 10N to 15N between 24W and 30W.
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.

...TROPICAL WAVES...

A tropical wave is along 81W/82W from Cuba and 21N southward.
This wave has a complex past history, and it is likely that it may
have been related to T.S. Florence from several days ago. It also
has been interacting with an upper level cyclonic circulation
center that is in the eastern Gulf of Mexico. Isolated moderate to
locally strong rainshowers are from 13N northward from 76W
westward.

...MONSOON TROUGH/ITCZ...

The ITCZ is along 09N43W 09N50W 08N57W. Isolated moderate to
locally strong rainshowers are elsewhere from 08N to 12N from 36W
eastward. Rainshowers are possible elsewhere from 10N southward
between 36W and 60W.



Hurricane Florence is centered near 24.4N 56.3W at 09/1500 UTC or
650 nm SE of Bermuda moving W at 5 kt. Estimated minimum central
pressure is 984 mb. Maximum sustained wind speed is 65 kt with
gusts to 80 kt. Florence will move over the southwestern Atlantic
Ocean between Bermuda and the Bahamas Tuesday and Wednesday, and
approach the southeastern U.S. coast on Thursday. Florence is
forecast to rapidly strengthen to a major hurricane by Monday, and
is expected to remain an extremely dangerous major hurricane
through Thursday. Scattered moderate to isolated strong convection
is from 22N-27N between 54W-60W. See latest NHC Public Advisories
issued under WMO header WTNT31 KNHC and under AWIPS header
MIATCPAT1. Forecast/Advisories are issued under WMO header WTNT21
KNHC and under AWIPS header MIATCMAT1.

Tropical Storm Isaac is centered near 14.3N 39.1W at 09/1500 UTC
or 1280 nm E of the Windward Islands moving W at 8 kt. Estimated
minimum central pressure is 999 mb. Maximum sustained wind speed
is 55 kt with gusts to 65 kt. Isaac is expected to become a
hurricane later today or tonight. A westward motion is forecast to
continue through the end of the week, with Isaac expected to move
across the Lesser Antilles and into the eastern Caribbean Sea on
Thursday. Scattered moderate to isolated strong convection is from
11N-17N between 37W-42W. 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 13.2N 25.0W at 09/1500 UTC
or 100 nm SSW of the Southernmost Cabo Verde Islands moving W at
11 kt. Estimated minimum central pressure is 997 mb. Maximum
sustained wind speed is 55 kt with gusts to 65 kt. A Tropical
Storm Warning is in effect for the Cabo Verde islands of Santiago,
Fogo, and Brava. Additional strengthening is forecast during the
next 48 hours, and Helene is expected to become a hurricane later
today. Scattered moderate to isolated strong convection is from
09N-18N between 20W-28W. 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.

...TROPICAL WAVES...

A tropical wave is along 86W from S of 21N, moving W at 15 kt.
This wave has a complex past history, and it is likely that it may
have been related to T.S. Florence from several days ago.
Scattered moderate to strong convection is from 13N-22N between
78W-86W.

...MONSOON TROUGH/ITCZ...

The ITCZ is west of T.S. Isaac from 07N46W to the coast of South
America near 06N58W. Scattered moderate convection is from 06N-
09N between 26W-41W.

...DISCUSSION...

GULF OF MEXICO...

An upper level low is centered over the E Gulf of Mexico near
25N87W. Scattered showers are E of 87W. An upper level ridge is
over the W Gulf W of 92W with northerly upper level flow.
Scattered showers are over the NW Gulf and the Texas coast W of
94W. At the surface, 5-10 southerly flow covers the Gulf.

Weak ridging from the Carolinas to the Texas coast will shift N
over the SE United States. A trough will move west off the Yucatan
coast each evening and dissipate over the SW gulf each morning.
The trough will be accompanied by moderate to fresh winds.

CARIBBEAN SEA...

A large upper level high is centered over the central Caribbean
near 16N75W. A tropical wave is the main source of convection in
the W Caribbean. See above.

Tropical Storm Isaac near 14.5N 40.3W 997 mb at 5 PM
EDT moving W at 10 kt. Maximum sustained winds 60 kt gusts 75 kt.
Isaac will strengthen to a hurricane near 14.6N 42.2W Mon morning,
move to 14.8N 45.0W Mon afternoon, 14.9N 48.0W Tue morning, 14.9N
50.9W Tue afternoon, and 15.0N 56.5W Wed afternoon. Isaac will
weaken to a tropical storm near 15.5N 63.0W Thu afternoon, and
change little in intensity as it moves to the central Caribbean
near 15.5N 69.5W Fri. Otherwise, relatively weak ridging over the
western Atlantic will maintain moderate to fresh trade winds over
most of the region through Mon night.

ATLANTIC OCEAN...

Please read the SPECIAL FEATURES section for details about
Hurricane Florence, T.S. Isaac, and T.S. Helene.

Hurricane Florence near 24.4N 57.0W 975 mb at 5 PM EDT moving W
at 6 kt. Maximum sustained winds 75 kt gusts 90 kt. Florence will
move to 24.6N 58.3W Mon morning, 25.1N 60.4W Mon afternoon, 25.9N
63.1W Tue morning, 27.0N 66.2W Tue afternoon, and 30.3N 72.6W Wed
afternoon. Florence will change little in intensity as it moves to
33.5N 77.5W Thu afternoon, and weaken to a tropical storm while
moving inland over 35.0N 79.0W Fri. Otherwise, a weak pressure
pattern across the SW N Atlc will maintain gentle to moderate
mainly easterly winds across the area through Mon.


Isolated moderate convection is over the W Atlantic from 26N-30N
between 72W-79W to include the N Bahamas. A small 1016 mb high is
over the W Atlantic near 25N68W. A small upper level low is near
30N70W. A 1013 mb low is centered near 30N70W. A 1025 mb high is
over the E Atlantic near 34N27W.

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

$$
mrf/nr/mt
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