[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 062333
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN SEP 06 2015

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
2330 UTC.

...SPECIAL FEATURES...

THE REMNANTS OF FRED ARE CENTERED NEAR 26.5N 42.5W AS OF 06/2100
UTC...MOVING TOWARD THE NNE AT 9 KT. THE MINIMUM CENTRAL
PRESSURE IS 1011 MB. MAXIMUM SUSTAINED WIND SPEED IS 25 KT WITH
GUSTS TO 35 KT. THIS IS THE LAST PUBLIC ADVISORY ABOUT FRED.
ISOLATED CONVECTION IS FROM 24N-28N BETWEEN 40W-43W.

THE CENTER OF TROPICAL STORM GRACE AT 06/2100 UTC IS NEAR 13.2N
31.2W. GRACE IS MOVING TOWARD THE W AT 13 KT. THE MINIMUM
CENTRAL PRESSURE IS 1002 MB. MAXIMUM SUSTAINED WIND SPEED IS 45
KT WITH GUSTS TO 55 KT. SCATTERED MODERATE FROM 08N TO 16N
BETWEEN 26W AND 32W. PUBLIC ADVISORIES ABOUT GRACE ARE BEING
ISSUED UNDER THE WMO HEADER WTNT32 KNHC...AND UNDER THE AWIPS
HEADER MIATCPAT2. FORECAST/ADVISORIES ARE BEING ISSUED UNDER THE
WMO HEADER WTNT22 KNHC...AND UNDER THE AWIPS HEADER MIATCMAT2.
SCATTERED MODERATE FROM 12N-14N BETWEEN 30W-32W.

...TROPICAL WAVES...

A TROPICAL WAVE IS OVER THE CENTRAL ATLANTIC WITH AXIS ALONG 40W
FROM 08N-16N MOVING W AT APPROXIMATELY 15 KT OVER THE PAST 24
HOURS. CIRA LAYER PRECIPITABLE WATER IMAGERY SHOWS DRY AIR IN
THE WAVE ENVIRONMENT WHICH COINCIDES WITH A SAHARAN AIRMASS
DEPICTED IN METEOSAT ENHANCED IMAGERY. A CLUSTER OF MODERATE
CONVECTION IS FROM 12N-14N BETWEEN 39W-42W.

A TROPICAL WAVE IS AT ABOUT 460 NM E OF THE LESSER ANTILLES WITH
AXIS EXTENDING FROM 16N53W TO 11N53W...MOVING W AT AROUND 15 KT.
THIS IS A LOW-AMPLITUDE WAVE WITH A WELL DEFINED INVERTED-V WIND
PATTERN AT 700 MB AND A WEAK CYCLONIC SWIRL NEAR THE SURFACE.
CIRA LAYER PRECIPITABLE WATER IMAGERY SHOW MODERATE MOISTURE
ASSOCIATED WITH THIS WAVE MAINLY S OF 14N WHERE SCATTERED
CONVECTION IS OBSERVED BETWEEN 53W-60W.

A TROPICAL WAVE IS OVER THE E CARIBBEAN WITH AXIS EXTENDING FROM
19N68W TO 12N70W...MOVING W AT 15 TO 20 KT OVER THE PAST 24
HOURS. CIRA LAYER PRECIPITABLE WATER IMAGERY SHOWS A MODERATE
AIRMASS AHEAD OF THE WAVE AXIS AND DRY AIR BEHIND IT. NO
CONVECTION IS OBSERVED ALONG THIS FEATURE AT THIS TIME.

A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN WITH AXIS
EXTENDING FROM 20N75W TO 11N77W...MOVING W AT 15 TO 20 KT OVER
THE PAST 24 HOURS. THE WAVE IS ASSOCIATED MAINLY WITH LOW TO MID
LEVEL MODERATE MOISTURE ACCORDING TO CIRA LAYER PRECIPITABLE
WATER IMAGERY. HOWEVER...STRONG DEEP LAYER WIND SHEAR AND
SUBSIDENCE FROM ALOFT IS HINDERING ANY SIGNIFICANT CONVECTION AT
THE TIME.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH PASSES OVER COASTAL SECTIONS OF AFRICA NEAR
15N17W TO 12N26W. THE ITCZ BEGINS NEAR 10N42W AND CONTINUES TO
10N62W. ASIDE FROM THE CONVECTION ASSOCIATED WITH GRACE AND THE
TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS OFF THE
WESTERN COAST OF AFRICA FROM 09N-16N AND E OF 20W...WHICH IS
ASSOCIATED WITH THE NEXT TROPICAL WAVE THAT WILL SOON COME OFF
THE COAST.

...DISCUSSION...

GULF OF MEXICO...

A BROAD SURFACE RIDGE COVERS THE EASTERN CONUS AND EXTENDS A
RIDGE AXIS ACROSS THE NE GULF WATERS. A WEAKNESS IN THIS RIDGE
IS ANALYZED AS A 1015 MB LOW LOCATED NEAR 27N85W. ALOFT...A
BROAD ANTICYCLONE IS CENTERED OVER TEXAS EXTENDING SE ACROSS THE
WESTERN GULF WHILE AN ELONGATED UPPER-LEVEL LOW IS CENTERED OVER
THE NE GULF NEAR 27N88W AND EXTENDING ACROSS THE REMAINDER OF
THE BASIN. THIS UPPER-LEVEL FEATURES ARE SUPPORTING SCATTERED
MODERATE CONVECTION ACROSS MOST OF THE AREA...MAINLY E OF 95W.
SCATTEROMETER DATA DEPICTS LIGHT AND VARIABLE WINDS ACROSS THE
GULF. WEAK RIDGING WILL CONTINUE ACROSS THE BASIN OVER THE NEXT
24-48 HOURS.

CARIBBEAN SEA...

ALTHOUGH TWO TROPICAL WAVES ARE OVER THE BASIN...NONE OF THESE
ARE PRODUCING ANY SIGNIFICANT WEATHER AT THE TIME. SEE THE
TROPICAL WAVES SECTION FOR MORE DETAILS. THE EASTERN PORTION OF
AN UPPER-LEVEL TROUGH EXTENDS FROM THE GULF OF MEXICO ACROSS THE
W CARIBBEAN SUPPORTING ISOLATED CONVECTION ACROSS THE AREA
AFFECTING CUBA AND JAMAICA. THE PROXIMITY OF THE MONSOON TROUGH
ACROSS THE SOUTHERN CARIBBEAN IS SUPPORTING SCATTERED MODERATE
CONVECTION MAINLY S OF 11N BETWEEN 76W-82W. THE REMAINDER BASIN
IS DEVOID OF CONVECTION BEING INFLUENCED BY DRY AIR SUBSIDENCE
AND STRONG DEEP LAYER WIND SHEAR. SCATTEROMETER DATA DEPICTS
GENTLE TO MODERATE TRADES ACROSS THE AREA BECOMING FRESH S OF
13N BETWEEN 72W-78W. OVER THE NEXT 24 HOURS...THE WAVES WILL
CONTINUE MOVING W. CONVECTION IS STILL EXPECTED ACROSS THE W
CARIBBEAN AS THE UPPER-LEVEL TROUGH PREVAILS ACROSS THE GULF OF
MEXICO.

...HISPANIOLA...

SHALLOW MOISTURE AND A MID TO UPPER-LEVEL DIFFLUENT ENVIRONMENT
ALOFT SUPPORT ISOLATED CONVECTION OVER CENTRAL HISPANIOLA THIS
EVENING. THIS ACTIVITY WILL DISSIPATE OVERNIGHT. THE PASSAGE OF
TWO TROPICAL WAVES OVER THE ISLAND IS EXPECTED TO GENERATE SOME
SHOWERS THROUGH THE NEXT COUPLE DAYS.

ATLANTIC OCEAN...

THE MAIN FEATURES IN THE BASIN ARE THE REMNANTS OF FRED AND
TROPICAL STORM GRACE...BOTH DISCUSSED IN THE SPECIAL FEATURES
SECTION. TWO TROPICAL WAVES ARE AHEAD OF GRACE...NONE OF THEM
ARE GENERATING SIGNIFICANT WEATHER AT THE TIME. PLEASE REFER TO
THE TROPICAL WAVES SECTION FOR MORE DETAILS. A SURFACE TROUGH IS
ANALYZED ACROSS THE W ATLANTIC FROM 23N78W TO 29N68W. ISOLATED
CONVECTION IS OBSERVED ALONG THIS FEATURE. TO THE E...A MID TO
UPPER-LEVEL TROUGH OVER THE CENTRAL ATLANTIC WITH BASE REACHING
NEARLY 30N SUPPORTS A WEAK STATIONARY FRONT THAT EXTENDS FROM
29N67W TO 31N49W. ISOLATED CONVECTION PREVAILS IN THE VICINITY
OF THIS BOUNDARY MAINLY N OF 28N AND BETWEEN 42W-53W. A SURFACE
RIDGE AND FAIR WEATHER PREVAILS ACROSS THE E ATLANTIC E OF 40W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$

ERA
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