AXNT20 KNHC 211043
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
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.
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.
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.
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.
A tropical wave E of the island is producing scattered showers
over the Dominican Republic. Expect showers over the entire
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