[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 120542
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT SEP 12 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 09N25W TO 17N24W MOVING W AT 15 KT.
THE WAVE COINCIDES WITH LOW AMPLITUDE 700 MB TROUGHING S OF 14N
BETWEEN 19W-27W. WITH THE SAHARAN AIR LAYER AND DUST LARGELY
INFLUENCING THE NORTHERN PORTION OF THE WAVE AND MUCH OF THE
EASTERN TROPICAL ATLC...ISOLATED MODERATE CONVECTION REMAINS
CONFINED TO THE MONSOON TROUGH REGION IN THE VICINITY OF THE
WAVE AXIS FROM 08N-10N BETWEEN 26W-32W.

TROPICAL WAVE EXTENDS FROM 10N42W TO 18N40W MOVING W AT 15 KT.
THE WAVE COINCIDES WITH A BROAD 700 MB TROUGHING BETWEEN 37W-
46W. ISOLATED MODERATE CONVECTION IS FROM 08N-14N BETWEEN 40W-
45W.

TROPICAL WAVE EXTENDS FROM 12N65W TO 20N65W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH A 700 MB TROUGHING BETWEEN 62W-68W
AND A 850 MB RELATIVE VORTICITY MAXIMUM NEAR 17N66W. NUMEROUS
MODERATE AND SCATTERED STRONG CONVECTION IS FROM 15N-20N BETWEEN
63W-67W. ISOLATED MODERATE CONVECTION IS ELSEWHERE FROM 13N-17N
BETWEEN 60W-64W.

TROPICAL WAVE EXTENDS FROM 09N78W TO 17N77W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH SUBTLE 700 MB TROUGHING OVER THE
WESTERN CARIBBEAN SEA. NO SIGNIFICANT DEEP CONVECTION IS
OCCURRING WITH THE WAVE AT THIS TIME.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 17N16W TO
08N30W TO 11N42W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
EXTENDS FROM 11N42W TO 10N61W. SCATTERED MODERATE AND ISOLATED
STRONG CONVECTION IS FROM 15N-18N BETWEEN 14W-18W. SCATTERED
MODERATE CONVECTION IS FROM 05N-10N BETWEEN 30W-35W. ISOLATED
MODERATE CONVECTION IS FROM 06N-14N BETWEEN 43W-56W.

...DISCUSSION...

GULF OF MEXICO...
BROAD MIDDLE TO UPPER LEVEL LONGWAVE TROUGHING IS NOTED ON WATER
VAPOR COVERING MUCH OF THE CENTRAL AND EASTERN CONUS WITH THE
BASE OF THE TROUGH DIPPING OVER THE NW AND NORTH-CENTRAL GULF
WATERS THIS EVENING. PLENTIFUL MID-LEVEL ENERGY IS N OF 26N AND
ALONG WITH THE UPPER LEVEL DIFFLUENCE AHEAD OF THE TROUGH
AXIS...CONTINUES TO GENERATE SCATTERED SHOWERS AND TSTMS FROM
23N-29N BETWEEN 92W-101W...INCLUDING INLAND PORTIONS OF NE
MEXICO. IN ADDITION...SCATTERED SHOWERS AND ISOLATED TSTMS ARE
OCCURRING N OF 26N BETWEEN 84W-90W. WHILE MUCH OF THE CONVECTION
REMAINS ELEVATED...WEAK SURFACE TROUGHING ANCHORED BY A 1014 MB
HIGH CENTERED NEAR 28N85W CONTINUES TO PROVIDE GENTLE
ANTICYCLONIC BREEZE CONDITIONS OUTSIDE OF THE ACTIVE CONVECTION.
THE WEAK FRONTAL BOUNDARY SUPPORTED BY THE UPPER LEVEL TROUGHING
IS EXPECTED TO SWEEP ACROSS THE NORTHERN GULF WATERS SATURDAY
INTO EARLY SUNDAY AND MOVE EAST OF THE BASIN BY MONDAY.

CARIBBEAN SEA...
MIDDLE TO UPPER LEVEL RIDGING IS OVER MUCH OF THE WESTERN
CARIBBEAN ANCHORED NEAR 17N86W PRODUCING OVERALL DRY AND STABLE
CONDITIONS ALOFT...HOWEVER THE PRESENCE OF A TROPICAL WAVE ALONG
78W AND THE MONSOON TROUGH AXIS ALONG 09N IS PROVIDING FOCUS FOR
ISOLATED SHOWERS AND TSTMS GENERALLY S OF 16N BETWEEN 74W-84W.
FARTHER EAST...AN UPPER LEVEL TROUGH INFLUENCES THE EASTERN
CARIBBEAN BETWEEN 62W-73W. GIVEN THE TROPICAL WAVE ALONG
65W...THE REMNANTS OF GRACE...AND THE FAVORABLE UPPER LEVEL
DIFFLUENT ENVIRONMENT EAST OF THE TROUGH AXIS...NUMEROUS SHOWERS
AND SCATTERED STRONG TSTMS ARE OCCURRING ACROSS THE NE CARIBBEAN
THIS EVENING. THE WAVE IS EXPECTED TO CONTINUE MOVING WESTWARD
AND BRING INCREASED PROBABILITIES OF PRECIPITATION TO PUERTO
RICO...THE MONA PASSAGE...AND HISPANIOLA ON SATURDAY.
OTHERWISE...MODERATE TO FRESH TRADES PREVAIL AND ARE EXPECTED TO
INCREASE SLIGHTLY ACROSS THE CENTRAL CARIBBEAN WITH THE
APPROACHING TROPICAL WAVE ON SUNDAY.

...HISPANIOLA...
CURRENTLY MOSTLY CLEAR SKIES AND FAIR CONDITIONS PREVAIL...
HOWEVER THE PRESENCE OF A TROPICAL WAVE ALONG 65W WILL BRING AN
INCREASE IN CLOUDINESS AND PROBABILITY OF PRECIPITATION AND
CONVECTION ON SATURDAY. SOME OF THE RAINFALL WILL BE HEAVY AT
TIMES AND LIKELY RESULT IN FLASH FLOODING AND MUD SLIDES.

ATLANTIC OCEAN... MOST OF THE SW NORTH ATLC IS UNDER THE
INFLUENCE OF SURFACE RIDGING WITH AXIS EXTENDING FROM 30N50W W-
SW TO THE SW BAHAMAS NEAR 23N75W. WITH OVERALL WEST-
SOUTHWESTERLY FLOW ALOFT N OF 30N...AND A WEAKNESS IN THE SURFACE
RIDGING BETWEEN 75W-83W...SCATTERED SHOWERS AND ISOLATED TSTMS
ARE OCCURRING N OF 25N BETWEEN 75W-81W...WITH ISOLATED SHOWERS
MAINLY OF 30N BETWEEN 65W-77W. OTHERWISE...THE ONLY OTHER MAJOR
FEATURE IMPACTING THE SW NORTH ATLC IS THE REMNANTS OF
GRACE...ANALYZED AS A TROPICAL WAVE ALONG 65W. MOST OF THE
CONVECTION REMAINS S OF 20N...AND IS EXPECTED TO CONTINUE
WESTWARD ACROSS THE ADJACENT COASTAL ATLC WATERS OF PUERTO RICO
AND HISPANIOLA ON SATURDAY. FARTHER EAST...AN ELONGATED UPPER
LEVEL LOW IS CENTERED NEAR 28N47W AND IS SUPPORTING TWO AREA OF
CONVECTION ACROSS THE CENTRAL ATLC THIS EVENING. SCATTERED
SHOWERS AND TSTMS ARE NOTED FROM 24N-28N BETWEEN 49W-54W ON THE
WESTERN PERIPHERY OF THE UPPER LEVEL LOW AND ISOLATED SHOWERS
AND TSTMS ARE NOTED FROM 27N-31N BETWEEN 38W-42W IN ASSOCIATION
WITH A WEAK 1016 MB LOW CENTERED NEAR 27N38W.

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

$$
HUFFMAN
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