000
AXNT20 KNHC 211043
TWDAT 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
643 AM EDT Fri Jul 21 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 
1015 UTC.

...TROPICAL WAVES...

A tropical wave over the eastern Atlantic extends from 17N31W to 
04N32W, moving west at 20 kt. This wave is along the leading edge
of a deep pool of moisture off the coast of Africa. METEOSAT 
imagery along with SSMI Total Precipitable Water imagery show an 
extensive area of Saharan dry air and dust NW of the wave. The GFS
guidance shows a well-defined 700 mb trough with this wave. 
Scattered showers are within 120 nm of the wave axis.

A large amplitude tropical wave is over the central Atlantic with
axis from 24N54W to 08N55W, moving west at 15 kt. Total 
Precipitable Water imagery depicts deep moisture south of 24N 
between 50W-60W. Scattered moderate to isolated strong convection
is from 16N-21N between 53W-58W. A portion of this wave is 
forecast to move across the eastern Caribbean during the upcoming 
weekend, bringing increasing moisture and probabilities for 
scattered showers and thunderstorms with gusty winds.

A tropical wave is over the E Caribbean with axis from 19N64W to 
08N65W, moving west at 20 kt. SSMI Total Precipitable Water 
imagery shows only a slightly moist area from 10N-20N. There is a 
well defined 700 mb trough associated with this wave. Scattered 
showers are within 120 nm of the wave axis. This wave is capable 
of producing strong gusty winds as it moves west across the 
eastern Caribbean today, and across the central Caribbean on 
Saturday and Saturday night.

A tropical wave is over the W Caribbean Sea with axis from 19N81W
through Panama to the E Pacific at 05N82W. This wave is the 
remnant of former Tropical Storm Don. Abundant low level moisture
is S of 17N. A well defined 700 mb trough is also present. 
Scattered moderate to strong convection is along the coast of 
Nicaragua from 11N-15N between 80W-85W. The wave will move to
Central America today. Strong gusty winds will continue to be 
possible with the associated shower and thunderstorm activity. 

...ITCZ/MONSOON TROUGH...

The monsoon trough extends from 14N17W to 12N30W to 10N36W. The 
ITCZ then extends from 10N36W to 06N44W to 10N53W. The ITCZ
resumes W of a tropical wave near 10N57W and extends to 10N62W.
Aside from the convection associated with the tropical waves, 
scattered moderate convection is along the coast of W Africa from 
08N-15N between 10W-18W. Scattered moderate convection is along 
the ITCZ from 02N-11N between 43W-49W. 

...DISCUSSION...

GULF OF MEXICO...

A surface trough is over the Yucatan Peninsula from 21N90W to 
17N92W. Scattered showers are within 60 nm of the trough axis. The
remainder of the Gulf of Mexico has weak surface ridging. Radar 
imagery shows scattered showers over the NE Gulf. In the upper 
levels, a small upper level low is centered over Mexico near 
23N100W. Another small upper level low is centered over the 
Yucatan Peninsula near 21N91W. A third small upper level low is 
centered over N Florida near 29N93W. Expect in 24 hours for the 
third upper level low to move to the N central Gulf, with 
convection. In addition, expect scattered showers and 
thunderstorms to form over Florida and the N Gulf N of 23N during 
maximum heating Friday.

CARIBBEAN SEA...

The main features in the basin are the two tropical waves moving 
through the basin. See the section above for details. Scattered 
showers and isolated thunderstorms are seen over the far SW 
Caribbean within 120 nm of the coasts of Costa Rica and Panama due
to the proximity of the monsoon trough that currently extends 
along 10N. Mostly fair weather conditions are observed elsewhere, 
with areas of Saharan dust spreading westward across much of the 
waters mainly north of about 15N. 

...HISPANIOLA...

A tropical wave E of the island is producing scattered showers
over the Dominican Republic. Expect showers over the entire
island today. 

ATLANTIC OCEAN...

Two tropical wave are moving through the far southern waters. See
the Tropical Waves section above for details. Scattered showers 
and isolated thunderstorms are over the N Bahamas and the W 
Atlantic, N of 25N and W of 73W. A large 1025 mb high is centered
over the Central Atlantic near 35N40W with ridge axis extending 
SW to 28N70W. Of note in the upper levels, a small upper level 
lows is over the W Atlantic at 25N73W enhancing showers. Another 
upper level low is also centered over the central Atlantic near 
29N47W enhancing showers W of center. 

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

$$
Formosa