[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 011805
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
204 PM EDT Tue Aug 1 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.

...SPECIAL FEATURES...

Tropical Depression Emily is centered near 29.3N 78.9W or about
105 nm ENE of Cape Canaveral, Florida moving NE at 12 kt. Estimated
minimum central pressure is 1011 mb. Maximum sustained wind speed
is 25 kt with gusts to 35 kt. Latest satellite imagery shows a
partially exposed and small low-level circulation, with a recent
burst of scattered moderate convection within 30 nm of the center
over the east quadrant. NWS doppler radar imagery from JAX, MLB
and MFL show cloud lines containing scattered showers and
thunderstorms rotating into the elongated northeast to southwest
circulation of the tropical cyclone. Emily will continue to pull
away from the Florida peninsula today, and is forecast to reach
near 30.4N 77.5W early this evening with maximums sustained wind
speed of 30 kt with gusts to 40 kt and maintain intensity as it
reaches near 32.1N 75.1W early on Wednesday and continue to north
of 32N later on Wednesday. See the latest NHC forecast/advisory
under AWIPS/WMO headers MIATCMAT1/WTNT21 for more details.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis extending from
18N30W to 06N31W, moving west at 10-15 kt. This wave remains
embedded in an extensive area of Saharan dry air and dust
inhibiting convection at this time. Isolated showers and
thunderstorms are seen within 120 nm either side of the wave
near and south of the monsoon trough from 06N-12N

A central Atlantic tropical wave has its axis extending from
20N51W to 12N52W to 05N52W, moving west at 15 kt. This wave
has been exhibiting a well defined cloud pattern the past several
days as it advances westward. The latest visible satellite
imagery depicts a broad cloud pattern marked by low-level clouds
moving from northeast to east in direction west of the axis to
similar clouds moving from southeast to northwest direction east
of the wave axis. The 700 mb guidance from the GFS model also
depicts broad troughing with this wave. The SSMI TPW animation
imagery is highlighting a very large area of deep moisture east-
southeast of this wave to near 34W and south of 17N. Stable
conditions are noted north of 17N where the Saharan Air Layer
is present. Pockets of scattered moderate convection are ahead
of the wave to 58W from 10N-16N, and east of the wave to near
45W from 05N-16N. This wave is forecast to enter the far eastern
Caribbean Sea on Wednesday, and move across the rest of the
eastern Caribbean through Thursday and the central Caribbean
Thursday night and Friday. Scattered showers and thunderstorms
will accompany the wave with gusty winds.

A west-central Caribbean tropical wave has its axis extending
along 76W from 18N to 08N, moving west at about 13 kt. SSMI TPW
imagery shows that wave portion south of 15N is moving through
deep atmospheric content noted there, while the portion north of
15N is under a dry and stable environment. Scattered moderate
isolated strong convection ahead of the wave within 30 nm either
side of line from 12N77W to 14N80W. Scattered showers and isolated
thunderstorms are elsewhere within 120 nm east and 240 nm west of
the wave south of 15N. The wave will move across the remainder
of the central Caribbean Sea through tonight, and across the
western Caribbean through Thursday night.

...ITCZ/MONSOON TROUGH...The monsoon trough axis extends from the west coast of Africa
near 16N17W to low pressure of 1012 mb near 12N28W to 11N41W
to 11N45W to 09N54W, where scatterometer data indicates that ITCZ
begins and continues to just east of South America at 09N60W.
Aside from the convection associated with the tropical waves,
scattered moderate isolated strong convection is within 180 nm
south of the axis between 33W-35W.

Scattered moderate convection is well to the southeast of the
monsoon trough along and within 120 nm of the west coast of
Africa from 07N-11N.

...DISCUSSION...

GULF OF MEXICO...

In the upper levels, just about the entire basin is under
anticyclonic flow aloft associated with a large anticyclone
located over the south-Texas/Mexico border. The tail end of a
sharp upper trough extends along the eastern Atlantic seaboard
southwest to southern Florida. At the surface, a trough extends
from inland south-central Florida to 26N88W to the NW Gulf near
28N96W. A weak 1015 mb low is centered along the trough near
26N88W. The combination of a very moist and unstable air mass
along with the trough and upper level disturbances riding
southward in northerly upper flow is resulting in an increasing
area of scattered moderate isolated strong convection south of
the trough to 23N and between 85W-90W. Scattered showers and
isolated thunderstorms are elsewhere south of 26N and east of
90W, while isolated showers and thunderstorms are seen from 23N-
30N west of 90W. Light to gentle east-southeast winds are north of
the trough, while gentle to moderate south to southwest winds are
south of the trough east of 90W. Mainly gentle southeast winds
are over the SW Gulf, and light to gentle variable winds are over
the NW Gulf. A thermal trough that moved off the Yucatan Peninsula
last night is along 93W south of 21N. It has very limited
moisture, with only isolated showers possible within 60 nm of it.
Expect generally unstable weather over the much of the central and
eastern Gulf through Thursday as the surface that extends east to
west and 1015 mb low gradually lift north-northeast.

CARIBBEAN SEA...

A tropical wave is moving across the west-central Caribbean. See
the section above for details. The eastern portion of the eastern
Pacific monsoon trough stretches eastward to across southern
Panama and to NW Colombia. Aloft, a cyclonic shear axis is evident
from a small upper level low near 16N79W to across northeastern
Nicaragua. Abundant deep moisture and instability is present over
the SW Caribbean. The combination of these ingredients that are
in place is resulting scattered moderate to isolated strong
convective activity south of 16N and west of 80W. Isolated showers
and thunderstorms are noted elsewhere west of 67W. East of 67W,
an upper level disturbance moving quickly westward on the
southwest periphery of an upper anticyclone centered just to
the northeast of the Leeward Islands has generated a 45 nm wide
line of scattered moderate convection over the southeastern
Caribbean to the south of 16N between 62W-67W. This activity will
move across the rest of the eastern Caribbean through early
Wednesday, then across the central Caribbean during the rest of
Wednesday through Thursday while it decreases in coverage. Otherwise,
the current tropical wave, and the one presently over the central
Atlantic along with the close proximity of the eastern Pacific
monsoon trough will be the main features to bring unsettled
weather to much of the central and eastern Caribbean over the next
24-48 hours.

...HISPANIOLA...

Fair weather prevails across the island early this afternoon. An
increase in moisture is expected at this time as dry air aloft
is present mainly over the central and eastern sections of the
island. With daytime heating and local effects coming into play
later this afternoon, there is a possibility of scattered showers
and thunderstorms over some of the interior locations. Low-level
moisture attendant by scattered showers and thunderstorms is
forecast to increase from the southeast late on Wednesday and
through Thursday as a broad tropical wave moves through the
eastern and central Caribbean areas.

ATLANTIC OCEAN...

Two tropical waves are moving across the tropical North Atlantic.
See the Tropical Waves section above for details. Aloft, a sharp
upper deep layer trough stretches from near 32N78W southwest to
southern Florida, and supports a stationary front that extends
along a position from 32N76W to just northeast of Tropical
Depression Emily. Persistent moderate convection is observed
over much of the northwestern portion of the basin to the
northwest of a line from 32N72W to southern Florida. Scattered
showers and isolated thunderstorms are seen over much of the
southeastern Bahamas. Isolated showers and thunderstorms are
elsewhere west of 70W. The majority of this activity is expected
to remain quite active through Thursday as the present synoptic
set up changes little. Otherwise, the remainder of the basin is
under the influence of a broad surface ridge, anchored by a nearly
stationary 1027 mb high that is analyzed near 33N44W.

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

$$
Aguirre
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