[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 042334
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
734 PM EDT Mon Sep 4 2017

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
2100 UTC.

...SPECIAL FEATURES...

Hurricane Irma is centered near 16.7N 54.4W at 04/2100 UTC or
about 425 nm E of the Leeward Islands moving W at 11 kt.
Estimated minimum central pressure is 944 mb. Maximum sustained
wind speed is 115 kt with gusts to 140 kt. Numerous strong
convection is within 120 nm of the center. Scattered moderate
convection is elsewhere from 14N to 19N between 50W and 58W.
Warnings and watches have been issued for the Leeward Islands,
Virgin Islands and Puerto Rico. Some strengthening is forecast
during the next 48 hours. See the latest NHC Intermediate Public
Advisory under AWIPS/WMO headers MIATCPAT1/WTNT31 KNHC and the
full Forecast/ Advisory under AWIPS/WMO headers MIATCMAT1/WTNT21
KNHC for more details.

A tropical wave is in the central Atlc associated with a 1010 mb
low located near 09N36W. The wave axis extends from 15N36W to the
low to 04N36W, moving W at 10 kt. The wave is a low amplitude
wave. SSMI TPW imagery shows the wave is in a very moist area. The
wave is also within a distinct 700 mb trough. Scattered moderate
convection is over a large area from 08N to 12N between 34W and
39W. Environmental conditions are expected to be conducive for
gradual development, and there is a medium chance for tropical
cyclone formation within the next 48 hours.

A surface low is expected to form off Tampico Mexico along a
trough in the western Gulf over the next 12 to 24 hours. There is
a medium chance for tropical cyclone formation within the next 48
hours.

...TROPICAL WAVES...

A tropical wave is along the coast of W Africa from off the north
coast of Senegal to 07N18W, moving W at 10 kt. SSMI TPW imagery
shows the wave is in a very moist area. The wave is also within a
distinct 700 mb trough. Scattered moderate convection is from 06N
to 12N between 15W and 20W.

A tropical wave is in the western Caribbean from western Cuba to
central Panama, moving W at 10 to 15 kt. SSMI TPW imagery shows
the wave is in a moderately moist area. The wave is also within a
distinct surface and 700 mb trough. Scattered moderate convection
is over the SW Caribbean south of 11N.

...ITCZ/MONSOON TROUGH...

The monsoon trough extends from the African coast near Gambia to
the 1010 mb low pressure near 09N36W to 20N45W. Another section of
monsoon trough reaches from the central coast of Colombia across
the southwest Caribbean along 11N to Costa Rica. No significant
convection is noted outside of what was already mentioned near
tropical waves.

...DISCUSSION...

GULF OF MEXICO...

A surface is analyzed across the far western Gulf from off Tampico
to off Veracruz Mexico. Moderate to fresh southeast winds are
noted across the central Gulf between the surface trough and 1019
mb high pressure centered near 27N85W. Clusters of moderate
convection are observed over the southwest Gulf S of 26N and W of
93W, fueled in part by deep layer moisture over the southwest Gulf
and divergent flow aloft in the right rear entrance region of a
jet max aloft across the northern Gulf. Expect the convection
over the SW Caribbean to persist. Also expect increased convection
over S Florida and the Straits of Florida over the next 24 hours.

CARIBBEAN SEA...

Hurricane Irma is a major hurricane approaching the Leeward
Islands. See Above. A tropical wave is entering the western
Caribbean. See above. In addition, the eastern extent of the E
Pacific monsoon trough traverses Costa Rica and Panama
intersecting with the tropical wave. 10-15 kt tradewinds are over
the remainder of the Caribbean Sea. Expect the Leeward Islands to
be under the influence of Hurricane Irma over the next 36-60
hours.

...HISPANIOLA...

Divergent flow between an upper ridge to the north and an upper
trough south of Hispaniola is enhancing scattered showers and
thunderstorms across the higher terrain of the island this
afternoon. Looking ahead, Hurricane Irma is forecast to approach
the Island early Thursday. See Special Feature for further
details.

ATLANTIC OCEAN...

Major Hurricane Irma continue to represent a threat for the
Leeward Islands. See special features for further details. The
tail end of a cold front is over the W Atlantic from 31N73W to
29N77W. A few showers and thunderstorms were active across the
northern Bahamas and adjacent waters, but this has largely
diminished in the past couple of hours. Farther east, an upper low
is centered near 27N62W, supporting a few showers and
thunderstorms from 28N to 30N between 60W and 65W, and well to the
north of Irma from 25N to 26N between 54W and 58W. Another upper
low is centered in the eastern Atlc near 27N33W. This may be
enhancing convection to some extent near the low pressure farther
south near 09N36W, but otherwise has little impact on sensible
weather at the surface due to lower moisture levels across the
eastern Atlc. Elsewhere, the subtropical ridge is fairly weak
north of the region in the central Atlc, allowing only gentle to
moderate trade winds east across the deep tropics east of Irma.

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

$$
Christensen
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