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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

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