[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 021801
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
201 PM EDT Wed Aug 2 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 1200 UTC surface analysis and satellite imagery through
1745 UTC.

...TROPICAL WAVES...

An eastern Atlantic tropical wave extends its axis from 18N34W to
14N35W to 06N35W, moving west at 10-15 kt. Dry Saharan air
surrounding this wave's environment is suppressing deep
convection from developing along or near it. The northern portion
of the wave appears to be tilting to the northeast as suggested
by the 700 mb streamline guidance from the GFS model. Isolated
showers are possible near where the wave crosses the monsoon
trough.

A central Atlantic broad tropical wave extends its axis from
22N60W to 15N60W to inland South America at 06N59W, moving west at
15-20 kt. The CIMSS total precipitable water imagery (TPW)
animation shows an extensive area of very deep moisture trailing
the wave to near 50W from 10N-15N. Scattered moderate isolated
strong convection in clusters is within this area of moisture.
This activity is likely attendant by strong gusty winds. Similar
activity precedes the wave into the eastern Caribbean to near 64W,
and is also likely to contain strong gusty winds as it quickly
moves westward. Wind gusts to 30-35 kt were reported this morning
in some of the Leeward Island locations. Fresh to locally strong
east to southeast winds will follow in behind the wave as it moves
across the eastern Caribbean through Friday. The Saharan Air
Layer imagery shows dry air and dust to the north and northeast of
the deep moisture area that follows the wave.

A western Caribbean tropical wave extends its axis from 19N84W to
inland eastern Honduras and continues south-southeast to the
eastern portions of Nicaragua and Costa Rica. The CIMSS TPW shows
very deep moisture within 120 nm east of the south of 15N.
Scattered moderate isolated strong convection is within this
moisture area. Isolated showers and thunderstorms are within 60
nm either side of the wave axis north of 15N. The scattered
moderate isolated strong convection is forecast to spread inland
Honduras, Costa Rica and Panama through this evening.

...ITCZ/MONSOON TROUGH...

The monsoon trough axis extends from the coast of African near
14N16W to 10N26W to 11N39W to 11N48W, where scatterometer data
indicates the ITCZ begins and continues to 11N59W. Scattered
moderate isolated strong convection is within 120 nm south of
the monsoon trough between 43W-45W. Scattered moderate convection
is within 240 nm south of the monsoon trough between 20W-25W,
within 120 nm south of the trough between 38W-43W, and well
south of the monsoon trough within 30 nm either side of line
from 08N15W to 07N20W.

Scattered moderate to strong convection is inland and off the
coast of Africa from 07N-11N. This activity is ahead of the next
tropical wave that is expected to emerge off the coast of Africa
in the near future.

...DISCUSSION...

GULF OF MEXICO...

A surface trough is analyzed from NE Florida southwest to just
north of Tampa, and continues southwest to a 1014 mb low at 28N86W
and southwest to near 26N91W. A 1016 mb small low recently formed
just offshore the northern Florida coast near 29.5N83W as of 15Z.
In the upper levels, very strong westerly winds are evident north
of 29N, while moderate to strong north to northeast winds around
the eastern periphery of a large upper anticyclone centered over
far northern Mexico are to the south of 29N. The resultant speed
diffluence ishelping to support scattered moderate isolated
strong convection over the eastern Gulf from 26N-29N east of the
1014 mb. Scattered moderate convection has recently developed over
the western Gulf within 30 nm of 26N94W, and within 60 nm of
29N93W. Scattered showers and isolated thunderstorms are elsewhere
north of 25N, while isolated showers and thunderstorms are south
of 25N. A thermal trough moved offshore the Yucatan Peninsula last
night, and is along 93W/94W south of 22N. Isolated showers are
possible within 30-60 nm of the trough. Scatterometer data depicts
a light to gentle cyclonic flow across the basin, with higher
speeds in and near the convection near the aforementioned lows.
Expect for the surface trough to drift north over the next 24
hours with convection. The surface low near 28N86W is expected to
drift northeastward through tonight while gradually dissipating
into Thursday morning. The low just offshore the northern Florida
coast will move inland this afternoon. The surface trough will
slowly lift northward and weaken through Thursday night in
response to an upper trough that digs southward over the central
U.S. Unsettled weather is expected through Friday over much of the
central and eastern Gulf.

CARIBBEAN SEA...

A tropical wave is moving across the far western Caribbean. See
the section above for details. Isolated showers are noted over the
western half of Cuba and the Yucatan Channel. Scattered moderate
isolated strong convection in clusters cover much of the central
and eastern Caribbean between 64W-76W. This activity has
significantly increased since yesterday, and is being supported
marginal speed diffluence aloft that is occurring on the southern
periphery of an upper anticyclone centered just north of the Mona
Passage. An inverted mid-upper level troughs near 66W and 74W are
helping to provide additional instability and support to this
activity as it quickly moves westward. The activity will spread
across the rest of the central Caribbean through tonight and the
western Caribbean Thursday through Friday. A tropical wave is just
east of the Lesser Antilles, and is preceded by similar
convection as what is currently being observed over the central
Caribbean. This convection reaches westward to near 64W, and is
expected to spread westward over the eastern Caribbean through
Thursday.

The pressure gradient associated with sub-tropical Atlantic high
will support fresh to strong winds across the north-central
Caribbean Sea and Windward Passage through Saturday. Little
change is expected elsewhere.

...HISPANIOLA...

Scattered to locally broken low clouds with developing isolated
showers and thunderstorms are over the interior of the central
portion of the Dominican Republic, and over some locations in
Haiti, mainly the northern and southern sections. As the afternoon
wears on and daytime heating becomes prolonged, expect for shower
and thunderstorm activity to increase over some of the interior
locations. Scattered showers and thunderstorms over much of
the central and eastern Caribbean are expected to stay south of
Hispaniola, for the most part, but some may approach or move
over the southern section of the island this evening and through
much of Thursday.

ATLANTIC OCEAN...

Two tropical waves are moving across the Atlantic basin. The one
along 60W will cross into the eastern Caribbean Sea this
afternoon. See the sections above for details. The southern
portion of an upper trough extends from near 32N77W to the central
and NW Bahamas. Scattered showers and thunderstorms are east of
the trough north of 28N between 67W-75W. Other scattered shower
and thunderstorm activity is just inland and along the coast of NE
Florida. The remainder of the basin is under the influence of a
surface ridge, anchored by a 1026 mb high centered north of
the area near 34N25W, another 1026 mb high at 32N40W and a 1025 mb
high at 30N56W. Generally dry and stable conditions under the
influence of the Saharan Air layer are present elsewhere east of
about 70W and north of the tropical waves. The Saharan Air Layer
is more evident over the central and eastern portions of the
basin. Scattered showers and thunderstorms are expected to
remain active over the northwest portion through Thursday night.

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

$$
Aguirre
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