Tropical Weather Discussion
Issued by NWS
AXNT20 KNHC 210007
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 PM EDT SAT AUG 20 2016
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 1800 UTC surface analysis and satellite imagery through
Tropical Storm Fiona is centered near 21.2N 49.1W at 20/2100 UTC
or about 760 nm east-northeast of the Leeward Islands, moving
northwest at 13 kt. Estimated minimum central pressure is 1008
mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt.
Scattered moderate to strong convection is from 21N-23N between
47W-50W. Please see the latest NHC Intermediate Public Advisory
under AWIPS/WMO headers MIATCPAT1/WTNT31 KNHC and the full
Forecast/Advisory under the AWIPS/WMO headers MIATCPAT1/WTNT21
KNHC for more details.
A tropical wave is just inland of western Africa with axis from
20N15W to a 1010 mb low near 13N16W to 06N15W, moving west at 10-
15 kt. This wave is in a very moist area as seen on SSMI Total
Precipitable Water Imagery. The wave and surface low also has a
700 mb signature. Clusters of scattered moderate to isolated
strong convection are from 07N-15N between 12W-19W.
Environmental conditions appear conducive for gradual
development. This system is likely to become a tropical
depression in a few days while it moves generally west-
northwestward over the eastern tropical Atlantic Ocean.
A tropical wave extends across the central Atlantic with axis
from 18N37W to a 1009 mb low near 12N38W to 05N38W, moving west
at 15 kt. Intrusion of Saharan dry air and dust across the
eastern portion of the wave is inhibiting convection in this
area, while scattered moderate convection prevails west of the
wave`s axis from 07N-15N between 38W-45W. Development during the
next couple of days should be slow to occur due to its large
size and proximity to dry air. Environmental conditions are
forecast to be more conducive for development beyond a couple of
days, and a tropical depression could form by the middle of next
week while the system moves westward across the tropical
Atlantic Ocean and into the eastern Caribbean Sea.
A tropical wave is moving across the eastern Caribbean with axis
from 19N68W to 10N69W, moving west at 20 kt. Strong dry air
subsidence from aloft and Saharan dry air in the wave
environment are limiting convection development at this time.
A tropical wave is moving across the western Caribbean and
Central America with axis from 20N86W to 09N87W, moving west at
20 kt. TPW imagery depicts the wave embedded in a moist
environment, however, strong dry air subsidence from aloft and
unfavorable deep-layer wind shear limits the convection to
isolated showers mainly south of 15N.
The Monsoon Trough extends across Africa into the east Tropical
Atlantic near 13N17W to 10N28W to through the 1009 mb low near
12N38W to 09N49W. The ITCZ begins near 09N49W to the coast of
South America near 09N61W. Aside from the convection associated
with the tropical waves, isolated moderate convection is from
06N-09N between 49W-57W.
GULF OF MEXICO...
Weak surface ridging prevails across the Gulf waters N of 22N,
anchored by a 1017 mb high near 28N85W. The ridge provides a gentle
variable flow across the E-NE basin while E-SE gentle to
moderate flow prevails elsewhere. An elongated upper-level low
centered over the NE Gulf near 29N87W supports isolated showers
and thunderstorms across Florida. Dry air subsidence and
unfavorable deep-layer wind shear supports fair weather
elsewhere. Little change is expected for the next 24 hours.
Two tropical waves are moving across the basin. Please refer to
the section above for details. Scatterometer data depicts
moderate to fresh trades across the basin except fresh to strong
winds from 11N-14N between 73W-78W. Scattered moderate
convection prevails across the southern Caribbean south of 11N
between 79W-84W as the Monsoon Trough extends over Panama and N
Colombia. Clusters of scattered moderate convection are inland
over Central America from 13N-20N. Similar convection is over E
Cuba and Hispaniola. Expect the waves to continue to move west
with minimal convection. Little change is expected elsewhere.
Moisture associated with the passage of a tropical wave and
divergent flow aloft will support clusters of scattered moderate
convection across the island. Mostly fair weather is expected
The primary concern in the Atlantic waters S of 30N continue to
be Tropical Storm Fiona and the tropical waves. Please see the
special features section, and the tropical wave section, above
for details. A 1017 mb high is centered east of the Bahamas near
24N69W. Another 1025 mb high is centered off the coast of
Portugal near 41N15W. In the upper levels a small upper level
low is centered near 31N45W supporting showers.
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