AXNT20 KNHC 290004
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
804 PM EDT WED SEP 28 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 Matthew at 29/0000 UTC was centered near 13.9N
62.4W or about 80 NM...145 KM W of St. Lucia moving west at 14 KT.
Maximum sustained winds have increased to 55 KT with gusts to 65 KT.
Estimated minimum central pressure was 1004 mb. The overall cloud
envelope of Matthew is quite large with scattered to numerous
strong convection extending out to 180 NM in the SE semicircle.
Scattered moderate isolated strong convection extended out to 240
NM elsewhere in the SE and 90 NM in the NW semicircles. Fort de
France, Martinique reported wind gusts to 52 KT within the past
few hours. Matthew is forecast to slowly strengthen over the next
24 hours...possibly becoming a hurricane by THU night or early
FRI. Please refer to the NHC forecast/advisory under AWIPS/WMO
headers WTNT24 KNHC/TCMAT4, or visit the NHC website at
http://hurricanes.gov for additional details.
Tropical wave with axis along 30W/31W from 06N to 18N is moving
westward at 10 to 15 KT. The wave is difficult to discern in TPW
imagery and is embedded in an areas of strong SAL. As such
convection is limited along the wave axis.
A new low-amplitude tropical wave was analyzed along 43W from 05N
to 16N. The placement of the wave was based on satellite
hovmoller and easterly wave diagnostics. Scattered moderate
isolated strong convection was noted within 180 NM east of the
wave axis from 08N to 12N. The wave also coincided with a surge
in the TPW imagery.
A tropical wave extends across the western Caribbean with axis
along 80W/81W from Panama to 16N, moving westward at 10 to 15 KT.
The wave is moving beneath an upper- level low currently centered
near 16N82W. Scattered moderate convection is observed in the area
where the wave interacts with the Monsoon Trough mainly south of
12N between 78W-82W.
The Monsoon Trough extends over Africa reaching the east Atlantic
near 14N17W through 10N24W to 08N41W. Scattered moderate to strong
convection is observed from 06N-13N between 17W-26W. Isolated
showers or thunderstorms prevail along the remainder of the
GULF OF MEXICO...
An expansive upper-level anticyclone is centered over eastern
Mexico near 23N98W. The associated anticyclonic flow dominated
almost all of the basin, except for the far northeastern portion.
The base of an extensive deep-layered trough was sweeping
southeast along the periphery of the anticyclone across southern
Alabama and the Florida peninsula. Abundant deep layered moisture
was noted over the Gulf W of 90W S of 26N. At the surface, a cold
front extends from near Panama City Florida through 28.5N90W to
28N94W. A surface trough extended from 28N95W to 19N95W. Scattered
moderate isolated strong convection prevailed along the surface
trough affecting the waters from 20N to 24N between 92W and 94W.
To the northeast, scattered showers are observed north of 26N and
east 89W. Gentle to moderate southeasterly winds prevail across
the basin except for light northwest winds NW of the cold front.
The cold front is forecast to continue moving east with showers
and thunderstorms over Florida with the surface trough over the
Bay of Campeche continuing to enhance convection.
An expansive upper-level anticyclone centered over eastern Mexico
near 23N98W is providing northerly flow aloft over the Caribbean
W of 83W. Broad troughiness prevails over the Caribbean between
70W and 83W with an embedded cyclonic circulation near 16N82W.
This feature was enhancing convection from 11N- 14N and west of
82W affecting portions of Nicaragua. Another circulation was
located just N of Hispaniola near 23N71W. A large anticyclone
centered over the Atlantic near 18N58W and associated flow
prevailed over the Caribbean E of 70W. This was providing a
favorable environment in the vicinity of Tropical Storm Matthew
which has entered the far eastern Caribbean. The associated mid
and high level cloudiness is spreading as far west as 68W. For
additional information on Matthew please refer to the special
features section above. Elsewhere, tropical wave along 80W/81W S
of 16N was producing scattered showers and thunderstorms over
the SW Caribbean and adjacent land areas. The Monsoon Trough
extends along 10N between 75W-80W with scattered moderate
An upper-level low just northeast of the island near 23N71W was
supporting isolated convection over the interior of the Dominican
Republic and Haiti. Tropical Storm Matthew is forecast to pass
south of Hispaniola by Friday. Cloudiness associated with Matthew
is expected to spread over the island early THU with an increase
in showers and thunderstorms late THU into FRI. The large envelope of
Matthew may result in the potential for locally heavy rains over
Hispaniola. This will greatly depend on the ultimate track of
Matthew. For additional information on Matthew please refer to
the special features section above.
An extensive mid-to upper level anticyclone centered near 18N58W
covers the Atlantic basin between 50W and 66W with an upper level
low centered near 23N71W. Downstream, a broad upper level trough
dominates the tropical Atlantic between 20W and 50W with an upper
level cyclone centered near 22N38W. At the surface, T.S. Matthew
has moved west of the Atlantic basin. A surface trough extends
across the west Atlantic from 31N75W to Andros Island. Scattered
moderate convection was noted within 180 NM east of the trough.
The remainder of the basin is under the influence of a surface
ridge anchored by a 1034 mb high centered near 40W43W.
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