[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 081012
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
612 AM EDT Sat Jul 8 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 0600 UTC surface analysis and satellite imagery through
0945 UTC.

...TROPICAL WAVES...

A tropical wave is over the far eastern Atlantic with axis extending
from 16N22W to 12N24W to 05N25W, moving westward around 10 kt.
The wave is in a region of favorable to neutral wind shear. Atmospheric
moisture continues to increase along and to the east of the wave.
The Meteosat 9 imagery along with depicts an extensive area of
African Saharan dry air and dust to its west. Convection remains
limited to across the far southern extent of the wave axis where
it intersects the monsoon trough axis and south of the trough
axis. It consists of the scattered moderate to strong type
intensity within 180 nm west of the axis from 05N-07N. Scattered
moderate convection is within 180 nm east of the axis from 05N-
08N.

A tropical wave, remnants of Tropical Depression Four, is over
the central Atlantic with its axis extending from near 22N54W to
19N54W to 13N55W. It is moving west-northwest around 18 kt. The
atmospheric environment surrounding the wave is very moist as
observed on the Total Precipitable Water (TPW) loop series. Also,
the CIRA moisture analysis reveals the presence of deep layer
moisture over and near the wave. Deep convection is pulsing along
the wave axis. This convection is observed as a large cluster of
the scattered moderate type intensity from 17N-19N between 54W-
56W. Scattered moderate convection is ahead of the wave within 30
nm of 20N58W. An Ascat pass from 0110Z last night nicely depicted
a northeast to southeast wind shift across the wave axis, with
fresh to strong east to southeast winds east of the axis from 17N-
20N between the wave and 50W. The wave is forecast to pass to the
northeast of the Leeward Islands by Sunday evening attendant with
possible brief gusty winds and squalls over portions of the
northeast Caribbean. It is then forecast to approach the SE
Bahamas on Monday.

A tropical wave is over the Caribbean Sea with axis extending
from 19N69W to 15N70W to inland Venezuela near 10N70W, moving
westward around 18 kt. The wave is entering an upper level
environment of neutral to unfavorable wind shear. The latest water
vapor imagery shows subsidence and and associated dry air over
and around the wave environment. Isolated showers and thunderstorms
moving quickly to the west are seen east of the wave, and also to
the west of the wave north of 16N and westward to just east of
Jamaica.

A tropical wave is over the Bay of Campeche and over southeastern
Mexico with axis extending from near 24N92W to inland Mexico at
18N94W. It is moving westward near 16 kt. The wave is embedded in
a very moist and unstable atmospheric environment. Clusters of
scattered moderate to strong convection are south of 22N and west
of the wave to along and just inland the coast of Mexico.
Scattered moderate convection is within 60 nm east of the wave
south of 20N. The wave is forecast to move across the remainder of
the SW Gulf through early this evening, then move inland Mexico
tonight.

...ITCZ/MONSOON TROUGH...

The Monsoon Trough axis extends from 16N17W to 09N23W to 05N35W.
The Intertropical Convergence Zone extends from 05N35W to 03N13W
to 03N43W to 04N52W. Aside from the convection related to the
tropical wave over the far eastern Atlantic. Scattered moderate
to strong convection is along and within 120 nm south of the axis
between 28W-32W, and within 60 nm north of the axis between 35W-
36W. Scattered moderate convection is within 60 nm north of the
axis between 30W-34W, between 38W-40W and within 60 nm south of
the axis between 43W-46W.

A surface trough is just north of the ITCZ along a position from
07N41W to 03N42W. Scattered moderate convection is within 90 nm
west of the trough from 03N-05N.

Scattered moderate to strong convection in clusters are along and
just offshore the coast of Africa from 07N-11N. This activity
extends inland as swell for 60 nm, and is in advance of the next
tropical wave forecast to approach the coast in the near future.

...DISCUSSION...

GULF OF MEXICO...

A tropical wave is over the Bay of Campeche and extends southward
to southeastern Mexico. See above for details on its associated
convection. A 1019 mb high is centered over the eastern Gulf near
27N84W. It is producing light to gentle anticyclonic winds across
the eastern part of the Gulf north of 26N. Water vapor imagery
indicates that a small upper level low is near 25N84W, and is
trending to shift southward. Ample present moisture and
instability to its east and southeast is bringing scattered
showers and isolated thunderstorms to the SE Gulf waters.
Isolated showers and thunderstorms are occurring to its northeast
and east. Scattered showers and isolated thunderstorms are also
over the western Gulf north of the deep convection associated with
the tropical wave. This activity is noted from 21N-28N and west
of 90W.

CARIBBEAN SEA...

A tropical wave axis is near 70W. See above for details.
Scattered moderate convection earlier along and near the coast of
Cuba is dissipating. Isolated showers and thunderstorms are seen
north of 18N between 77W-82W. Scattered moderate to isolated
strong convection is over the SW Caribbean south of 14N and west
of 79W. This activity will persist through the weekend. In the
upper levels, anticyclonic flow covers the western half of the
sea, while a small upper low is situated over the central part of
the Caribbean. Southerly upper flow is present east of the upper
low. This is transporting upper debris cloudiness from deep
convection over Venezuela northward to portions of the eastern
half of the Caribbean. Isolated showers and thunderstorms are
developing over some sections of the eastern Caribbean in very
moist easterly trade wind flow. Additional showers and
thunderstorms are expected to develop through the weekend. The
analyzed pressure gradient supports 10-15 kt trades across the
Caribbean, except for stronger winds in the 20-25 kt range along
the coast of Colombia. These conditions will continue into early
next week.

...HISPANIOLA...

Scattered showers and thunderstorms moving west-northwestward
over the eastern section of Hispaniola have increased in coverage
due to the approach of the tropical wave as discussed above. This
activity is expected to continue to affect most of eastern
Hispaniola, and some areas of the central section of the island
through the weekend. Scattered showers and thunderstorms over
the southwestern portion of Haiti are mainly the result of a
small upper level low between Haiti and Jamaica acting on
very moist and unstable tropical air present through the region.
This activity is expected to continue through today, with a good
chance it may expand eastward as added moisture from the
aforementioned tropical wave approaches.

ATLANTIC OCEAN...

The remnants of Tropical Depression Four, now a tropical wave,
is over the central tropical Atlantic and a tropical wave is over
the far eastern tropical Atlantic. See above for details on these
features. Otherwise, strong high pressure of 1030 mb is centered
north of the discussion area at 35N37W moving northwest. It
extends a ridge southwestward to 32N50W and to central Florida.
The ridge will change little through Sunday, then begin to lift
back to the north on Monday. Water vapor imagery shows an
elongated upper low (TUTT) centered near 29N55W lifting
northward. A large upper anticyclone is near 29N70W. Scattered
showers and thunderstorms are southeast and south of the upper low
from 22N- 25N between 52W-57W. Isolated showers and thunderstorms
are noted from 25N-29N between 51W-53W. Scattered showers and
isolated thunderstorms moving northwestward in very moist
southeast flow along the southwest periphery of the ridge axis are
over the western part of the area south of 28N and west of about
75W. An extensive area of African Saharan dust is situated over
the eastern and central Atlantic E of 53W, and is gradually
migrating westward.

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

$$
Aguirre
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