[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 150005
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 PM EDT Fri Sep 14 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
2345 UTC.

...SPECIAL FEATURES...

Tropical Storm Florence is centered near 34.0N 78.6W at 14/2100
UTC, about 40 nm WSW of Wilmington North Carolina moving W at 3
kt. Estimated minimum central pressure is 972 mb. The maximum
sustained winds are 60 kt with gusts to 75 kt. Latest satellite
imagery shows that Florence is exhibiting a rather symmetrical
cloud pattern. Scattered moderate to isolated strong convection
is within 180 nm of the center in the NE quadrant and within 120
nm of the center in the SE quadrant. Scattered moderate
convection within an outer rainband is within 30 nm of a line from
33N79W to 34N81W and to 36N81W. Latest NHC advisory has Florence
moving in a slow westward to west- southwestward expected motion
though Sat. On the forecast track, the center of Florence will
move farther inland across extreme southeastern North Carolina
this evening, and across extreme eastern South Carolina tonight
and Sat. Florence will then move generally northward across the
western Carolinas and the central Appalachian Mountains early next
week. The PUBLIC ADVISORIES for Florence are transmitted via the
WMO header WTNT31 KNHC, and via the AWIPS header MIATCPAT1. The
FORECAST/ADVISORIES for Florence are transmitted via the WMO
header WTNT21 KNHC, and via the AWIPS header MIATCMAT1.

Tropical Storm Helene is centered near 34.1N 36.8W at 14/2100 UTC
or 550 nm WSW of Lajes Air Base In The Azores moving N at 16 kt.
Estimated minimum central pressure is 988 mb. Latest satellite
imagery shows scattered moderate convection from 35N to 39N
between 31W and 39W. Helene is forecast to move toward the north
through tonight, with a turn toward the north-northeast expected
early Sat followed by a turn toward the northeast by Sun morning.
On the forecast track, Helene will pass near or over the Azores
late Sat or Sun. The PUBLIC ADVISORIES for Helene are transmitted
via the WMO header WTNT33 KNHC, and via the AWIPS header
MIATCPAT3. The FORECAST/ADVISORIES for Helene are transmitted via
the WMO header WTNT23 KNHC, and via the AWIPS header MIATCMAT3.

Tropical Storm Joyce centered near 31.4N 44.1W at 14/2100 UTC or
930 nm WSW of the Azores moving SE at 5 kt. Estimated minimum
central pressure is 1002 mb. Maximum sustained winds are 40 kt
with gusts to 50 kt. Latest satellite imagery shows increasing
convection, with a vigorous band now near the center in the
northern semicircle. The convection consists of the scattered
moderate type intensity within 180 nm of the center in the NE
quadrant, and within 90 nm of the center in the NW quadrant. Joyce
is forecast by the latest NHC advisory to turn northeastward with
an increase in forward speed during the next 24 hours, followed
by an eastward turn after 48 hours The PUBLIC ADVISORIES for Joyce
are transmitted via the WMO header WTNT3S KNHC, and via the AWIPS
header MIATCPAT5. The FORECAST/ADVISORIES for Joyce are
transmitted via the WMO header WTNT25 KNHC, and via the AWIPS
header MIATCMAT5.

Tropical Storm Isaac centered near 15.3N 68.2W at 14/2100 UTC or
220 nm SSE of Santo Domingo Dominican Republic moving W at 12
kt. Estimated minimum central pressure is 1002 mb. Maximum
sustained winds are 35 kt with gusts to 45 kt. Latest satellite
imagery shows scattered moderate convection removed from the
center from 12N to 15.5N between 68W and 71W. Scattered moderate
convection is also seen to the east of Isaac from 14N to 17N
between 64W and 66W. Isaac is forecast by the Latest NHC advisory
to decrease its forward speed over the next couple of days with a
turn to the west- northwest possible by late on Sun. On the
forecast track, Isaac will move over the eastern and central
Caribbean Sea during the next few days, and be near or south of
Jamaica early next week. The PUBLIC ADVISORIES for ISAAC are
transmitted via the WMO header WTNT34 KNHC, and via the AWIPS
header MIATCPAT4. The FORECAST/ADVISORIES for ISAAC are
transmitted via the WMO header WTNT24 KNHC, and via the AWIPS
header MIATCMAT4.

...TROPICAL WAVES...

A far eastern tropical wave has its axis along 30W from 08N to
21N, moving westward at 10 to 15 kt. The wave is surrounding by a
rather dry environment, which is inhibiting deep convection from
forming along or near it. Only isolated showers and weak isolated
thunderstorms are within 120 nm either side of the wave axis where
it cross the monsoon trough.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from near 12N16W to 09N25W to
08N32W. The ITCZ continues from 08N32W to 09N41W to 10N46W to
12N57W. Aside from the shower and thunderstorm activity
associated with the tropical wave along 30W, scattered moderate
isolated strong convection is within 180 nm south of the ITCZ from
43W to 53W. Scattered moderate convection is within 180 nm south
of the monsoon trough from 18W to 23W, and within 180 nm south of
the ITCZ between 39W and 43W.

...DISCUSSION...

GULF OF MEXICO...

An upper-level cyclonic circulation center is over north- central
27N88W, with an inverted trough to an upper low over the
northwestern Caribbean at 20N84W that is moving westward. Upper-
level cyclonic wind flow covers the central part of the gulf. A
surface trough extends from inland central Texas to a 1009 mb low
along the coast just north of Brownsville and to 24N97W to
21N97W. Scattered moderate isolated strong convection is seen
from 22N to 29N west of 92W. Isolated showers and thunderstorms
cover the rest of the gulf. Heavy rainfall and gusty winds are
likely to continue across portions of Texas and northeastern
Mexico through Sat.

A NW-to-SE orientated surface ridge will set up from central
Louisiana to Florida Bay tonight. A surface high pressure center
will develop along the ridge near 27N92W late on Saturday. The
surface high will shift slightly southward on Sunday, and the
ridge will extend southeastward to the Yucatan Basin. A weak
surface trough, extending southwestward from the remnants of
tropical cyclone Florence, will pass eastward, slowly, across
the north central Gulf waters through early next week.

CARIBBEAN SEA...

Please refer to the the Special Feature section above for details
on Tropical Depression ISAAC.

An upper level cyclonic circulation center is about 100 nm to the
west of Jamaica, in the NW corner of the Caribbean Sea. Isolated
moderate rainshowers are from 15N northward from 80W westward.

Isolated moderate rainshowers cover the area that is between
70W and 80W.

Tropical Depression Isaac near 14.9N 67.3W 1007 mb at 11 AM EDT
moving W at 14 kt. Maximum sustained winds are 30 kt gusts 40 kt.
Isaac will move to 15.0N 69.0W this evening, 15.1N 71.3W Sat
morning, 15.2N 73.3W Sat evening, 15.6N 75.3W Sun morning, 17.0N
79.5W Mon morning and dissipate early Tue. The highest winds and
seas are expected mainly north of the center. Expect gentle to
moderate trade winds elsewhere, to the west of Isaac. Moderate to
locally fresh trade winds are forecast to the east of Isaac.
Strong nocturnal trade winds are forecast off the northwest coast
of Colombia on Monday night and on Tuesday night.

ATLANTIC OCEAN...

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

An upper level trough extends from 31N45W to 26N48W to 20N54W,
and to 16N56W. Upper level cyclonic wind flow is within 360 nm on
either side of the trough. Isolated moderate rainshowers are
in the area of upper level cyclonic wind flow.

A surface ridge will meander from 31N69W to southeast Florida
through Sunday. The ridge will shift northward, to a position from
31N74W to central Florida by the middle of the next week.

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

$$
McElroy
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