[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 031754
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
154 PM EDT Mon Jul 3 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
1715 UTC.

...TROPICAL WAVES...

A tropical wave is over the eastern Atlantic with axis near 22W
extending from 06N to 16N, moving westward 5-10 kt. No
significant deep convection is occurring near the wave. Only
isolated showers and thunderstorms are within 120 nm west of the
wave axis. The wave is embedded in a moist monsoonal flow, as seen
in the Total Precipitable Water imagery (TPW), and extends across
the monsoon trough. Little to no surface signature of the wave is
apparent from satellite imagery and limited surface observations,
though the SUNY-Albany Trough Diagnostics continues to exhibit
the wave at the 700 mb level.

A tropical wave is over the central Atlantic with axis near 33W
extending from 05N to 16N, moving west at about 5 kt within the
last 24 hours. A broad 1012 mb surface low is detached from the
wave, and is best satellite estimated position is near 09N32W
based on low-level cloud motion and on Ascat pass from this
morning. The wave remains noticeable at 700 mb in the Trough
Diagnostics. Dry and stable conditions are present north of about
12N in the vicinity of the wave, as seen in the Saharan Air Layer
imagery from Meteosat 9. Scattered moderate isolated strong
convection is seen from 08N and 11N between 32W and 35W, within
30 nm of line from 07N33W to 08.5N35W and within 90 nm southeast
quadrant of low. Scattered moderate convection is east of the
wave from 08N-11N between 29W-31W. Scattered showers and isolated
thunderstorms are elsewhere from 05N-12N between 27W-35W. The low
is forecast to remain about stationary through early Tuesday
before it takes on a northwesterly direction as the tropical wave
along 22W approaches from the east.

A tropical wave is fast approaching the Lesser Antilles moving
westward about 20 kt in the past 24 hours. Its axis is along 56W
from 08N to 18W. The wave is strongly identified in the Trough
Diagnostics, the Total Precipitable Water imagery, as well as in
observed low-level cloud cloud field. The northern portion of the
wave separate last night, and is analyzed as trough from near
28N52W to near 23N56W. Scattered showers and thunderstorms had
increased during the overnight hours with this wave from 11N-14N,
but have diminished to scattered showers and isolated thunderstorms
during this morning as the leading edge of some dry air originating
from the Saharan Air Layer present over the eastern Atlantic has
intruded into the wave environment. Scattered showers and isolated
thunderstorms are beginning to move over portions of the Leeward
Islands. This activity may be accompanied by gusty winds as it
moves across those islands, and also across the Windward Islands
and over the eastern Caribbean through this evening as the wave
nears the Lesser Antilles.

A tropical wave is quickly moving across the eastern Caribbean
with axis near 72W extending 08N to 18N, and moving westward
near 16 kt. A surface trough is following in behind the wave from
near 14N68W to 17N66W. There is slight evidence in the latest
visible imagery of low-level cloud motion shifting from northeast-
east west of the wave to east-southeast to the east of the wave.
The wave is embedded within a deep pool of moisture south of 18N
as observed in the Total Precipitable Water (TPW) animation.
Scattered showers and isolated showers are noted from 14N-18N west
of the wave to 75W, and from 15N-18N east of the wave to 69W.
Scattered showers and isolated thunderstorms are within 60 nm west
and 30 nm east of the surface trough. The wave will move across
the rest of the eastern Caribbean through this evening, and across
the central Caribbean through Tuesday night and western Caribbean
on Wednesday.

...ITCZ/MONSOON TROUGH...

The Monsoon Trough axis extends from the west coast of Africa
near 15N17W to 10N26W to the 1012 mb low near 09N32W and to
08N45W. The Intertropical Convergence Zone extends from 08N45W to
the coast of South America at 06N57W. Convection observed near
the Monsoon Trough and ITCZ is mainly related to tropical waves.
Refer to the section above for details. Otherwise, scattered
moderate convection is seen from 05N to 08N between 35W-40W.

Scattered moderate isolated strong convection is south of the
monsoon trough over the far eastern Atlantic from within 60 nm of
line from 08N15W to 08N22W, and within 60 nm of another line from
05N10W to 07N14W.

...DISCUSSION...

GULF OF MEXICO...

A 1021 mb surface high is analyzed over the north-central Gulf
near 28N90W, with a ridge to central Texas. This is the main
feature ion control of the weather pattern throughout. In the
upper levels, an elongated cyclonic circulation is evident near
23N93W with a trough to 29N96W and another one to just northwest
of the Yucatan Peninsula. Scattered showers and isolated
thunderstorms are noted over much of the Bay of Campeche and
portions of the SW Gulf. Moisture around the western periphery of
an upper level cyclonic circulation (TUTT) moving west just south
of central Cuba has infiltrated the southeastern part of the Gulf
where it has resulted in scattered showers and isolated
thunderstorms south of 26N and east of 86W. Similar activity
moving southwestward has developed over portions of the eastern
and central Gulf from 26N-28N. This activity will remain active
into the Tuesday. The activity over the southeast Gulf will
continue to spread westward through Wednesday. Otherwise, high
pressure will remain in place through the next 48 hours,
maintaining generally gentle to moderate east-southeast
throughout except for gentle winds from the west to northwest
in direction over the NE Gulf.

CARIBBEAN SEA...

An upper level cyclonic circulation (TUTT) is centered just south
of central Cuba, as seen in water vapor imagery. Weak high
pressure is present elsewhere, except for broad low pressure over
the SW Caribbean. The eastern segment of the eastern Pacific
monsoon trough reaches to NW Colombia. A tropical wave is along
72W as discussed above. Drier air and dust is noted between 63W-
66W. The pressure gradient across the basin supports mainly
moderate easterly winds, with the exception of strong easterly
winds near the coast of Colombia and from 11N-15N between 72W-
80W. The TUTT will slowly move west-northwest across the NW
Caribbean through Wednesday while weakening but will bring an
increase of moisture along with scattered showers and isolated
thunderstorms to the remainder of the NW Caribbean, Cuba and
portions of the northern Yucatan Peninsula. The gradient will
change little elsewhere through Wednesday, with winds remaining
about the same. Easterly winds will pulse from fresh to strong
over the south-central Caribbean through Wednesday.

The next tropical wave is quickly approaching the Lesser
Antilles, and is preceded by an easterly surge. Scattered showers
and isolated thunderstorms with gusty winds are presently moving
across the Leeward Islands, while isolated showers and
thunderstorms are just east of the Windward Islands. The wave will
enter the far east portion of the Caribbean early on Tuesday, and
move across the rest of the eastern Caribbean through Wednesday.

...HISPANIOLA...

Increasing moisture from a weak tropical wave just south of the
islands near 72W has resulted in scattered showers and thunderstorms
within 30 nm of 18N71W. Additional trailing the wave is expected
to increase showers and thunderstorms over portions of the
Hispaniola and the nearby waters through Tuesday.

ATLANTIC OCEAN...

Three tropical waves are analyzed over the basin. Refer to the
Tropical Waves section above for details. A surface trough
developed last night over the waters between the Bahamas and
central Cuba. This was in association with a well pronounced
upper-level cyclonic circulation (TUTT) observed on water vapor
imagery just to the south of central Cuba. Scattered showers and
thunderstorms are moving westward across the waters between Andros
Island and Cuba and extend west to the Straits of Florida. This
activity will continue to be rather active through most of Tuesday
as the TUTT pulls off to the west-northwest and weakens. Otherwise,
the remainder of the basin remains under the influence of a broad
high pressure ridge that stretches from a 1029 mb high north of
the area at 34N38W southwestward through 30N70W and to central
Florida. A weak surface trough is along a position from near
32N48W to 25N54W. This feature was induced by an upper-level
cyclonic circulation that is identified to be near 30N53W with a
trough extending to 25N58W and to near 20N69W. The cyclonic
circulation is forecast to move generally westward through Tuesday
before it begins to drop to the south. Isolated showers and
thunderstorms are seen along and west of the surface trough, and
also south of 25N west of 57W. The gradient associated with the
ridging is forecast to support gentle to moderate southeast to
south winds north of 25N, and moderate to fresh east to southeast
winds south of 25N through Wednesday.

An extensive area of Saharan African dust covers much of the
eastern and central Atlantic per the Saharan Air Layer imagery
from Meteosat 9. This in combination with the high pressure
present over the basin is keeping weather conditions very stable
north of the tropical waves. The dust will advect westward through
mid-week and approach the eastern Caribbean.

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

$$
Aguirre
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