[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 120027 CCA
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
756 PM EDT Tue Sep 11 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 27.5N 67.1W at 11/2100 UTC or
310 nm SSW of Bermuda moving WNW at 15 kt. Estimated minimum
central pressure is 945 mb. Maximum sustained wind speed is 120
kt with gusts to 145 kt. Latest satellite imagery shows numerous
strong convection near the center from 27N-30N between 66W-69W.
Scattered moderate to isolated stromg convection is elsewhere from
25N-31N between 64W-70W. A motion toward the west-northwest and
northwest is expected through early Thursday. Florence is expected
to slow down considerably by late Thursday into Friday. On the
forecast track, the center of Florence will move over the
southwestern Atlantic Ocean between Bermuda and the Bahamas through
Wednesday, and approach the coast of North Carolina or South
Carolina in the hurricane warning area on Thursday and Friday.
Florence is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Further strengthening is forecast tonight
and Wednesday. While some weakening is expected on Thursday,
Florence is forecast to be an extremely dangerous major hurricane
through landfall. 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 14.6N 51.3W at 11/2100 UTC
or 580 nm E of the Lesser Antilles moving W at 15 kt. Estimated
minimum central pressure is 996 mb. Maximum sustained wind speed
is 60 kt with gusts to 75 kt. Latest satellite imagery shows
numerous strong convection 13N-16N between 49W-51W. Scattered
moderate convection is elsewhere from 12N-18N between 48W-52W.
Isaac is anticipated to move near or over the central Lesser
Antilles on Thursday, move into the eastern Caribbean Sea Thursday
night, and move into the central Caribbean Sea by the weekend.
Isaac is expected to be near hurricane strength when it
moves through the central Lesser Antilles, with some weakening
forecast afterward on Friday and Saturday. 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.

Hurricane Helene is centered near 17.2N 34.9W at 11/2100 UTC or
630 nm W of the Cabo Verde Islands moving NW at 10 kt. Estimated
minimum central pressure is 968 mb. Maximum sustained wind speed
is 90 kt with gusts to 110 kt. Latest satellite imagery shows
scattered moderate to strong convection from 15N-22N between
32W-37W. Helene is forecast to turn toward the north-northwest
on Wednesday. Thereafter, Helene should recurve northeastward
with increasing forward speed. Helene should weaken to a
tropical storm on Thursday. 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.

An area of disturbed weather located over the extreme northwestern
Caribbean Sea and the southeastern Gulf of Mexico continues to show
some signs of organization.  Upper-levels winds are forecast to
become more conducive for development, and a tropical depression is
likely to form by Thursday night while the disturbance moves across
the western Gulf of Mexico.  If necessary, an Air Force
reconnaissance plane will investigate the system tomorrow.
Interests across northeastern Mexico and the coasts of Texas and
Louisiana should monitor the progress of this system. Regardless of
development, heavy rainfall and gusty winds are expected to continue
over western Cuba and portions of the northeastern Yucatan Peninsula
through tonight. This area of disturbed weather has a medium chance
for tropical cyclone formation over the next couple of days. Please
read the latest Tropical Weather Outlook under WMO header ABNT20
KNHC, and under the AWIPS header MIATWOAT for more details on this
evolving system.

...TROPICAL WAVES...

Tropical waves are not presently over water, however, the next
tropical wave expected to move across the discussion area waters
in the short-term is presently over the interior of Africa near
12W. Ahead of this wave, scattered moderate to isolated strong
convection is observed along the coast of W Africa from 08N-20N
between 12W-22W.

...MONSOON TROUGH/ITCZ...

The monsoon trough is non-continuous over the interior of
Africa. The western segment of the trough extends southwestward
from coast of Sierra Leone to 06N18W. The ITCZ is not analyzed
at this time.

...DISCUSSION...

GULF OF MEXICO...

See Special Features above for details on an area of disturbed
weather over the southeastern Gulf of Mexico.

A narrow upper-level trough extends from the northeastern part
of the Gulf of Mexico to the eastern central Gulf of Mexico and
to an upper-level low at 23N88W, It continues from the low to
inland the eastern Yucatan Peninsula. Associated upper cyclonic flow
is present south of 29N and east of 93W. Upper-level anticyclonic
wind flow covers the Gulf of Mexico west of 93W and the Atlantic
Ocean to 70W, and the Caribbean Sea from 15N northward from 70W
westward. Aside from the convection associated with the above
described area of disturbed weather over the southeastern gulf
waters, isolated showers and thunderstorms are noted elsewhere east
of 91W.

A stationary front stretches from southwestern Louisiana to inland
the southern Texas coast. Plenty of deep atmospheric moisture is
present over the far western gulf as a rather strong upper trough
moves across central Texas. Scattered moderate isolated strong
convection is noted north of 22N and west of a line from 30N91W to
25N94W to 22N95W. Scattered showers and isolated thunderstorms
are elsewhere west of 91W.

A surface trough in the western Caribbean Sea will move across
the Yucatan peninsula on Tue, and into the Gulf of Mexico on
Wed. The trough is expected to move into the western Gulf on
Thu and to the west of the area on Sat.

CARIBBEAN SEA...

A surface trough extends from the southeastern Gulf of Mexico near
25N84W to just inland the eastern section of the Yucatan
Peninsula. An upper-level trough extends from an upper-level low
just north of the Yucatan Peninsula south-southwestward to just
inland the peninsula. Plenty of available deep tropical moisture
along with the presence of these features has resulted in plenty
of atmospheric instability, leading to numerous moderate to strong
convection north of 18N and west of 81W, including western Cuba
and the Yucatan Channel. This activity is likely to be accompanied
by strong to near gale force gusty winds and very heavy rainfall
as it gradually lifts northward over the eastern and central Gulf
of Mexico through Thu. See Special Features section above for more
details on this area of disturbed weather. Scattered showers and
isolated thunderstorms are elsewhere north of 15N and west of 81W.

ATLANTIC OCEAN...

Please refer to the Special Features section above for details
on Hurricanes Florence and Helene and on Tropical Storm Isaac.

An upper-level trough extends from a nearly stationary upper-
level low near 31N34W southwestward to 26N40W, where it becomes a
cyclonic shear axis to a small upper-level low dropping south at
24N48W and to near 23N55W. Upper-level cyclonic flow covers the
area generally to the north of 23N between 26W and 54W. Scattered
showers and isolated thunderstorms are within 120 nm in the NE and
90 nm in the SW semicircles of the low near 24N48W, and also north
of 30N from 34W to 38W. Isolated showers and thunderstorms are
elsewhere west of 40W, except for scattered showers and isolated
thunderstorms north of 26N west of 74W enhanced by the combiation
of an inverted surface trough that is offshore the coast of
Florida from 26N79W to 31N81W, and an upper trough axis that
extends into the far northwest corner of the area from 32N79W to
northeastern Florida.

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

$$
Formosa
This weather bulletin was brought to you by:
www.nashvilleweather.net