[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 090230 CCA
TWDAT

Tropical Weather Discussion...CORRECTED
NWS National Hurricane Center Miami FL
1030 PM EDT Sat Sep 8 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.

Corrected to for T.S. Isaac information and to mention newly added
tropical wave.

Based on 1800 UTC surface analysis and satellite imagery through
2330 UTC.

...SPECIAL FEATURES...

The center of Tropical Storm Florence at 08/2100 UTC is near
24.6N 54.7W. Florence is moving W, or 270 degrees, 04 knots. The
estimated minimum central pressure is 989 mb. The maximum
sustained wind speeds are 60 knots with gusts to 75 knots.
Scattered moderate to strong rainshowers are observed within 90 nm
in the northern semicircle of from the center of the storm.
Florence is expected to move across the southwestern Atlantic
Ocean between Bermuda and the Bahamas on Tuesday and Wednesday,
and approach the southeastern U.S.A. coast on Thursday. Florence
is expected to intensify to a hurricane on Sunday, and intensify
more to a major hurricane by Tuesday. Please read the latest NHC
forecast/advisory under AWIPS/WMO headers MIATCPAT1/WTNT31 KNHC
for more details.

The center of Tropical Storm Helene at 09/0000 UTC is near
13.6N 22.2W. HELENE is about 200 km to the SE of Praia in the Cabo
Verde Islands. HELENE is moving W, or 275 degrees, 11 knots. The
estimated minimum central pressure is 998 mb. The maximum
sustained wind speeds are 50 knots with gusts to 60 kt.
Scattered to numerous strong rainshowers are from 11N to 14N
between 20W and 25W. Scattered moderate to isolated strong
rainshowers are elsewhere from 10N to 16N between 20W and 25W.
Please read the latest NHC forecast/advisory under AWIPS/WMO
headers MIATCPAT3/WTNT33 KNHC for more details.

Newly named Tropical Storm Isaac is centered near 14.5N 36.6W at
08/2100 UTC or 1430 nm E of the Windward Islands moving W at 6 kt.
Estimated minimum central pressure is 1005 mb. Maximum sustained
wind speed is 35 kt with gusts to 45 kt. Scattered moderate to
strong thunderstorms and rainshowers are observed within 120 nm NW
and 60 nm SE semicircles of Isaac. See latest NHC
forecast/advisory under AWIPS/WMO headers MIATCPAT4/WTNT34 KNHC
for more details.

...TROPICAL WAVE...
A tropical wave was introduced in the surface map at 1800Z between
central Panama and central Cuba. This as a complex past history
and was likely related to Florence several days ago. It has also
been interacting with an upper low now centered over the eastern
Gulf of Mexico. A few showers and thunderstorms are ongoing west
of the tropical wave axis, from San Andres Island to Grand Cayman
to eastern Honduras.

...MONSOON TROUGH/ITCZ...

The monsoon trough is along 11N40W 08N49W. The ITCZ continues from
11N40W to 07N58W. Isolated moderate to locally strong rainshowers
are elsewhere from 07N to 13N from 40W eastward. Rainshowers are
possible elsewhere from 10N southward between 40W and 60W.

...DISCUSSION...

GULF OF MEXICO...

An upper level low is centered over the SE Gulf of Mexico near
25N86W. A moist and unstable atmosphere over the SE Gulf and
Florida is producing widely scattered moderate convection over
the Straits of Florida from 23N-26N between 80W-85W. Upper level
diffluence is also over the W Gulf producing widely scattered
moderate convection from 22N-24N between 90W-94W. On the surface,
a trough is over the Straits of Florida from 25N80W to 23N84W.

Weak ridging from the Carolinas to the Texas coast
will shift N over the SE United States. Gentle to moderate E to
SE winds and modest seas will prevail through the middle of next
week. The exception will be fresh winds pulsing off west of the
Yucatan peninsula, mainly during the late evening.

CARIBBEAN SEA...

An upper-level trough axis stretches from western Cuba to
northeastern Honduras, and a broad upper level high is centered
over the central Caribbean near 14N74W. Scattered moderate
isolated strong convection is noted west of the upper level high,
roughly south of 16N and west of 74W.

Relatively weak surface ridging over the western Atlantic will
maintain moderate to fresh trade winds over most of the region
into Sun. Building surface high pressure over the eastern Gulf of
Mexico will allow fresh to locally strong E to SE winds and
building seas over portions of the NW Caribbean Sun through Tue.

ATLANTIC OCEAN...

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

An upper level low is centered over the W Atlantic near 30N71W.
Widely scattered moderate convection is from 27N-35N between 59W-
69W. Nearby Bermuda reported 1.25 inches of rainfall over 24
hours. A surface trough is over the W Atlantic from 31N75W to S
Florida near 26N81W. Widely scattered moderate convection is W of
75W.

A 1012 mb low is centered over the W Atlantic near 32N68W. A
surface trough extends S from the low to 28N72W. A 1021 mb high is
centered over the central Atlantic near 35N38W.

A weak pressure pattern will support gentle to moderate easterly
winds across the western Atlantic into early next week. Tropical
Storm Florence is forecast by the latest NHC advisory to move
across the northeastern TAFB offshore waters zones Mon through
Tue. Easterly swell well in advance of Florence will propagate
through the open waters east of the Bahamas this weekend.

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

$$
mrf/mt/ec
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