[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 121048
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 09N27W TO 17N24W MOVING W AT 10-15
KT. THE WAVE COINCIDES WITH LOW AMPLITUDE 700 MB TROUGHING S OF
14N BETWEEN 21W-30W. 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 07N-11N BETWEEN 22W-29W.

TROPICAL WAVE EXTENDS FROM 09N46W TO 16N45W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH A BROAD 700 MB TROUGHING BETWEEN 42W-
49W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 08N-14N
BETWEEN 42W-49W.

TROPICAL WAVE EXTENDS FROM 13N65W TO 20N65W MOVING W AT 15 KT.
THE WAVE COINCIDES WITH A 700 MB TROUGHING BETWEEN 62W-69W AND A
850 MB RELATIVE VORTICITY MAXIMUM NEAR 17N66W. SCATTERED
MODERATE CONVECTION IS FROM 14N-19N BETWEEN 63W-69W.

TROPICAL WAVE EXTENDS FROM 06N80W TO 15N80W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH SUBTLE 700 MB TROUGHING OVER THE
WESTERN CARIBBEAN SEA. ISOLATED MODERATE CONVECTION IS FROM 11N-
13N BETWEEN 74W-79W.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 18N16W TO
10N25W TO 07N34W TO 10N42W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 10N42W TO 10N46W TO 09N54W. SCATTERED MODERATE
CONVECTION IS FROM 15N-18N BETWEEN 15W-21W AND FROM 05N-10N
BETWEEN 30W-38W. ISOLATED MODERATE CONVECTION IS FROM 08N-14N
BETWEEN 40W-58W.

...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 MORNING. PLENTIFUL MID-LEVEL ENERGY IS N OF 25N AND
ALONG WITH THE UPPER LEVEL DIFFLUENCE AHEAD OF THE TROUGH
AXIS...THESE FEATURES CONTINUE TO GENERATE SCATTERED SHOWERS AND
TSTMS FROM 21N-28N BETWEEN 91W-100W...INCLUDING INLAND PORTIONS
OF NE MEXICO FOCUSED ALONG A SURFACE TROUGH BOUNDARY EXTENDING
FROM 28N90W TO 25N98W. IN ADDITION...SCATTERED SHOWERS AND
ISOLATED TSTMS ARE OCCURRING E OF 87W. WHILE THE MIDDLE TO UPPER
LEVEL FEATURES ARE THE PRIMARY SUPPORT OF THE ACTIVE
CONVECTION...WEAK SURFACE RIDGING EXTENDS ACROSS THE FLORIDA
STRAITS TO THE SOUTH-CENTRAL GULF NEAR 23N90W PROVIDING 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 16N86W PRODUCING OVERALL DRY AND STABLE
CONDITIONS ALOFT...HOWEVER THE PRESENCE OF A TROPICAL WAVE ALONG
80W IS PROVIDING FOCUS FOR ISOLATED SHOWERS AND TSTMS IN THE
VICINITY OF 12N77W. FARTHER EAST...AN UPPER LEVEL TROUGH
INFLUENCES THE EASTERN CARIBBEAN BETWEEN 62W-74W. GIVEN THE
TROPICAL WAVE ALONG 65W...THE REMNANTS OF GRACE...AND THE
FAVORABLE UPPER LEVEL DIFFLUENT ENVIRONMENT EAST OF THE TROUGH
AXIS...SCATTERED SHOWERS AND TSTMS ARE OCCURRING ACROSS THE
EASTERN CARIBBEAN THIS MORNING. 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
STRONG CONVECTION ON SATURDAY. SOME OF THE RAINFALL WILL BE
HEAVY AT TIMES AND LIKELY RESULT IN FLASH FLOODING AND MUD
SLIDES IN THOSE AREAS PRONE TO THESE HAZARDS.

ATLANTIC OCEAN...
MOST OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF SURFACE
RIDGING WITH AXIS EXTENDING FROM A 1020 MB HIGH CENTERED NEAR
29N55W W-SW TO THE CENTRAL BAHAMAS NEAR 24N77W. 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 28N BETWEEN 72W-80W. 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 28N48W AND IS SUPPORTING TWO AREAS OF
CONVECTION ACROSS THE CENTRAL ATLC THIS MORNING. SCATTERED
SHOWERS AND TSTMS ARE NOTED FROM 23N-29N BETWEEN 48W-56W ON THE
WESTERN PERIPHERY OF THE UPPER LEVEL LOW AND ISOLATED SHOWERS
AND TSTMS ARE NOTED FROM 27N-32N BETWEEN 38W-43W IN ASSOCIATION
WITH A WEAK 1017 MB LOW CENTERED NEAR 28N40W.

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

$$
HUFFMAN
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