056
AXNT20 KNHC 170440 CCA
TWDAT
TROPICAL WEATHER DISCUSSION...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN SEP 16 2018
CORRECTED SPECIAL FEATURES SECTION
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
2345 UTC.
..SPECIAL FEATURES
CORRECTED
TROPICAL DEPRESSION JOYCE IS CENTERED NEAR 34.4N 32.6W AT 16/2100
UTC OR 350 NM SW OF THE AZORES MOVING E AT 15 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1008 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT
WITH GUSTS TO 40 KT. LATEST SATELLITE IMAGERY SHOWS THAT JOYCE IS A
SHEARED SYSTEM AS NOTED BY ITS DEEP CONVECTION BEING SHEARED OFF TO
THE NORTHEAST OF ITS THE CENTER. THE CONVECTION IS DEFINED AS THE
MODERATE TYPE INTENSITY WITHIN 30 NM EITHER SIDE OF A LINE FROM
37N27W TO 36N30W TO 26N31W. OVERCAST TO BROKEN LOW AND MID-LEVEL
CLOUDS WITH EMBEDDED SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
ARE WELL TO THE EAST AND NORTHEAST OF JOYCE FROM 34N TO 38N BETWEEN
21W AND 27W. STRONG SOUTHWEST TO WEST WINDS ALOFT AND DRY AIR IN ITS
SURROUNDING ENVIRONMENT WILL CONTINUE TO HAMPER JOYCE OVER THE NEXT
FEW DAYS CAUSING IT TO GRADUALLY WEAKEN. JOYCE WILL CONTINUE ON ITS
PRESENT MOTION THROUGH TONIGHT, THEN IT IS FORECAST TO SLOW DOWN AND
TURN TOWARD THE SOUTHEAST AND THEN THE SOUTHWEST AWAY FROM THE
AZORES. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCPAT5/WTNT35 KNHC FOR MORE DETAILS.
..TROPICAL WAVES
A CENTRAL ATLANTIC TROPICAL WAVE HAS ITS AXIS EXTENDING ALONG 40W
BETWEEN 05N AND 20N, MOVING WESTWARD NEAR 15 KT. THE WAVE IS
SUPPORTED BY BROAD TROUGHING AT THE 700 MB LEVEL. EARLIER DUST
THAT SURROUNDED THE WAVE HAS THINNED OUT SINCE YESTERDAY AS A
SURGE OF LOW-LEVEL MOISTURE IS PRESENTLY SURGING WESTWARD ON
EITHER SIDE OF THE WAVE SOUTH OF THE WAVE AXIS. THIS MOISTURE HAS
LEAD TO SCATTERED SHOWERS AND THUNDERSTORMS MOVING QUICKLY
WESTWARD FROM 10N TO 12N BETWEEN 34W AND 38W, AND FROM 11N TO 14N
WITHIN 120 NM WEST OF THE WAVE AXIS. SIMILAR ACTIVITY IS WITHIN
60 NM EITHER SIDE OF THE WAVE IN THE VICINITY OF THE ITCZ REGION
FROM 05N TO 08N.
..MONSOON TROUGH/ITCZ
THE MONSOON TROUGH AXIS EXTENDS FROM WELL INLAND AFRICA SOUTHWESTWARD
TO THE COASTLINE NEAR 16N16W AND CONTINUES TO 09N22W. THE ITCZ
EXTENDS FROM 09N22W TO 06N30W TO JUST WEST OF THE TROPICAL WAVE
ALONG 40W. IT RESUMES AT 08N41W TO 07N49W TO 06.5N54.5W TO 07N59W.
ASIDE FROM THE SHOWER AND THUNDERSTORMS ACTIVITY ASSOCIATED WITH
THE TROPICAL WAVE DESCRIBED ABOVE, SCATTERED MODERATE ISOLATED
STRONG CONVECTION IS WITHIN 240 NM NORTH OF THE ITCZ BETWEEN 51W
AND 59W, AND WITHIN 150 NM SOUTH OF THE ITCZ BETWEEN 42W AND 48W.
SCATTERED MODERATE CONVECTION IS WITHIN 150 NM NORTH OF THE ITCZ
BETWEEN 48W AND 51W.
..DISCUSSION
GULF OF MEXICO...
IN THE UPPER-LEVELS, AND ELONGATED UPPER LOW IS OVER THE WESTERN
GULF NEAR 25N93W, WITH A TROUGH EXTENDING NORTHEASTWARD TO SOUTHERN
MISSISSIPPI, AND ANOTHER TROUGH FROM THE LOW TO THE EASTERN BAY OF
CAMPECHE. UPPER-LEVEL CYCLONIC FLOW COVERS THE BASIN WEST OF 86W.
ANTICYCLONIC FLOW ALOFT ASSOCIATED WITH AN UPPER-LEVEL
ANTICYCLONE OVER THE NORTHWESTERN CARIBBEAN NEAR 20N84W IS OVER
THE GULF EAST OF 86W. AT THE SURFACE, A TROUGH IS JUST INLAND THE
COAST OF MEXICO FROM 20N TO NEAR SAN FERNANDO. PLENTY OF
ATMOSPHERIC INSTABILITY ALONG WITH DEEP MOISTURE IN PLACE IS
LEADING TO SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS SOUTH OF
25N AND WEST OF 94W TO INLAND MEXICO, WHERE THE ACTIVITY INCREASES
TO SCATTERED IN COVERAGE. AT THE SURFACE, HIGH PRESSURE OF 1015
MB IS CENTERED NEAR 27N93W. RELATIVELY WEAK HIGH PRESSURE IS
ACROSS THE BASIN. A SURFACE TROUGH EXTENDS SOUTHWESTWARD FROM WHAT
IS NOW TROPICAL DEPRESSION FLORENCE LOCATED OVER THE BORDER OF
EASTERN GEORGIA, SOUTHWESTWARD TO OVER HE FLORIDA PANHANDLE.
SCATTEROMETER DATA FROM THIS AFTERNOON HIGHLIGHTED LIGHT TO GENTLE
ANTICYCLONIC FLOW WEST OF 87W, AND LIGHT TO MODERATE SOUTH TO
SOUTHWEST FLOW EAST OF 87W. LITTLE CHANGE IN THESE WINDS IS
EXPECTED THROUGH THE MIDDLE PART OF THE UPCOMING WEEK.
CARIBBEAN SEA...
A SURFACE TROUGH EXTENDS ACROSS THE CENTRAL CARIBBEAN FROM JUST
WEST OF HAITI TO A 1009 MB LOW AT 17N75W TO NEAR 11N77W. ABUNDANT
MOISTURE PREVAILS IN THIS AREA IS SUPPORTING SCATTERED MODERATE
TO STRONG CONVECTION FROM 15N TO 18N BETWEEN 73W AND 76W. THESE
FEATURES AND RELATED CONVECTION DENOTE A BROAD AREA OF LOW
PRESSURE ASSOCIATED WITH FORMER TROPICAL CYCLONE ISAAC. THIS AREA
OF LOW PRESSURE REMAINS DISORGANIZED.ONLY SLOW DEVELOPMENT WILL
BE POSSIBLE DURING THE NEXT DAY OR SO DUE TO PROXIMITY TO DRY AIR
AND LAND INTERACTION WITH JAMAICA. BY WED, ENVIRONMENTAL
CONDITIONS ARE FORECAST TO BECOME LESS CONDUCIVE FOR RE-
DEVELOPMENT TO OCCUR. REGARDLESS OF DEVELOPMENT, LOCALLY HEAVY
RAINS AND GUSTY WINDS WILL BE POSSIBLE OVER PORTIONS OF
HISPANIOLA, JAMAICA, AND EASTERN CUBA DURING THE NEXT COUPLE OF
DAYS WHILE THE SYSTEM MOVES WEST-NORTHWESTWARD TO WESTWARD TOWARD
THE NORTHWESTERN CARIBBEAN SEA. LATEST SCATTEROMETER DATA DEPICTED
GENTLE TRADES WEST OF THE TROUGH, WHILE GENTLE TO MODERATE TRADES
ARE ELSEWHERE EAST OF THE TROUGH. THE CENTRAL ATLANTIC TROPICAL
WAVE WILL MOVE ACROSS THE TROPICAL WATERS EAST OF THE WINDWARD
ISLANDS BY TUE, ACCOMPANIED BY FRESH WINDS AND BUILDING SEAS.
ATLANTIC OCEAN...
PLEASE REFER TO THE SPECIAL FEATURES SECTION ABOVE, FOR DETAILS
ON NOW TROPICAL DEPRESSION JOYCE.
A BROAD DEEP-LAYER TROUGH EXTENDS ACROSS THE CENTRAL ATLANTIC
FROM A LARGE AND ELONGATED UPPER-LEVEL LOW THAT IS NORTH OF THE
AREA NEAR 35N52W SOUTHWESTWARD TO 20N69W. PLENTY OF INSTABILITY
EXISTS WITH THIS TROUGH AS IT ACTS ON A VERY MOIST ATMOSPHERE.
THE TROUGH IS FORECAST TO MOVE WESTWARD DURING THE NEXT FEW DAYS.
AT THE SURFACE, A 1012 MB LOW IS NEAR 24N65W, WITH A TROUGH FROM
28N60W TO 24N66W. TO THE EAST, ANOTHER TROUGH EXTENDS FROM 27N55W
TO 22N60W. SCATTERED MODERATE CONVECTION IS NOTED WITH THESE
FEATURES BETWEEN 52W AND 66W. SURFACE RIDGING PREVAILS ACROSS THE
REMAINDER OF THE BASIN, ANCHORED BY A 1022 MB HIGH CENTERED NEAR
26N34W.
AN AREA OF AFRICAN DUST IS OVER THE EASTERN ATLANTIC FROM 10N TO
25N EAST OF 37W, AND IS GRADUALLY MIGRATING WESTWARD.
FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE
AGUIRRE
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