[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 250541
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
141 AM EDT Sat Aug 25 2018

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 0000 UTC surface analysis and satellite imagery through
0245 UTC.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis along  is
offshore the coast of Africa near 22W from 05N to 20N, moving
westward at 15 kt. The wave is in a low to mid-level moist
environment as observed in the total precipitable water satellite
animation. It is passing to the south of the 700 mb east to west
jet stream branch that extends from Africa westward to the eastern
Atlantic. Scattered moderate convection is within 120 nm east of
the axis from 05N to 07N.

A central Atlantic tropical wave has its axis along 49W/50W from
03N-18N, moving westward at 15 kt. The wave is moving through
a dry and stable environment which is inhibiting deep convection
from developing at this time near it. Only isolated showers are
noted within 120 nm either side of the wave axis from 02N to 07N.

An eastern Caribbean Sea tropical wave has its axis along 67W/68W
south of 18N to well inland S America, moving westward at 10-15
kt. Rather dry and stable conditions depict the surrounding
environment of this wave confirmed by the GOES-16 dust depiction
imagery. This a result of the Saharan Air Layer (SAL) that is
gradually pressing westward across the tropical Atlantic and
eastern Caribbean. The wave is void of deep convection. Scattered
moderate convection is over S America within 120 nm west of the
wave from 05N to 09N.

A western Caribbean Sea tropical wave has its axis along 84W/85W
south of 19N, moving westward at about 16 kt. Scattered moderate
isolated strong convection is over the eastern section of
Honduras, and extends northward to 18N and eastward over
the Caribbean waters from 15N to 18N. Scattered moderate
convection is within 30 nm of a line from 13N81W to 11N83W, and is
being mainly enhanced by a mid-level cyclonic circulation that is
behind the wave near 11N82.5W.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from the African coast near
15N17W to 08N28W to 09N36W to low pressure at 08N39W 1012 mb. The
ITCZ begins at 07N41W and ends just to the east of the wave along
49W/50W. Scattered strong convection is within 120 nm of the low
in the SW quadrant. Scattered moderate convection is within 120
north of the axis between 35W and 38W. Isolated moderate is within
60 nm south of the ITCZ between 41W and 42W.

...DISCUSSION...

GULF OF MEXICO...

An inverted upper-level trough over the southeastern gulf is
acting on very moist and unstable atmosphere, with the end result
bringing scattered showers and isolated thunderstorms to much of
that part of the gulf. Similar activity is noted south of 25N
between western Cuba and 88W. Scattered moderate convection with
the nocturnal Yucatan Peninsula trough is weakening over the far
eastern Bay of Campeche. Isolated showers and thunderstorms are
elsewhere over the area.

The pressure gradient across the Gulf supports generally light to
gentle east to southeast winds throughout, except for gentle to
moderate winds over the far southeast gulf and the northwest gulf
and moderate to locally fresh northeast to east winds in the
eastern Bay of Campeche into early next week.

CARIBBEAN SEA...

Two tropical waves are moving across the basin. Refer to the
section above for details. An upper-level low is centered near the
Gulf of Honduras at 17N86W. The low is assisting providing
additional support to convection associated with the tropical
wave along 84W/85W as described above. A mid-level cyclonic
circulation is evident in the southwestern part of the Caribbean
at 11N82.5W. This feature is entrenched in a very unstable and
moisture-laden atmosphere. This has developed scattered
moderate convection to the east of the aforementioned wave as
described above. This activity is expected to continue to increase
through the rest of the morning.

The pressure gradient between the central Atlantic high pressure
and broad low pressure over the southwestern Caribbean and S
America will result will bring fresh to strong trades to the
south-central Caribbean waters through early next week. The
passage of tropical waves will further tighten the pressure
gradient leading to strong to near gale force trades along the
coast of Colombia and Venezuela with seas building to 9 ft. A
tropical wave is forecast to move across the Lesser Antilles Tue
night into Wed accompanied by scattered showers and isolated
thunderstorms.

ATLANTIC OCEAN...

Two tropical waves are moving across the basin. Refer to the
section above for details. A weakening stationary front is off
the coast of northern Florida along a position from near 32N78W
to just east of NE Florida. A narrow upper-level trough extends
along the United States eastern seaboard southwestward to a small
upper-level low moving westward at 31N80W to inland NE Florida.
Latest satellite and radar imagery shows scattered moderate
convection north of 26N between 74W and 80W. An upper-level low
is centered east of the Bahamas near 24N75W, and is helping to
enhance this convective activity. A western Atlantic surface
trough extends from 26N64W to 20N66W. Scattered showers and
isolated thunderstorms are within 60 nm either side of the trough
from 23N to 25N, while isolated showers and thunderstorms are
elsewhere within 180-210 nm either side of the trough.

Another surface trough is analyzed over the central Atlantic
from near 31N38W to 25N41W. An upper-level low is located west of
the trough near 28N46W. Scattered showers and isolated
thunderstorms are seen from 28N to 30N between 42W and 47W.
Isolated showers are noted within 120 nm west of the surface
trough from 30N to 32N. Saharan dust and associated dry air is
noted mainly east of about 64W on the GOES-16 GEO color dust
imagery. The dust is suppressing convection from developing over
much of the central and eastern Atlantic waters, except as
described near tropical waves and near the monsoon trough and
ITCZ regions.

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

$$
Aguirre
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