[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171752
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI JUL 17 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 10N19W TO 17N18W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH A BROAD 700 MB TROUGH MOVING OFF THE
COAST OF WEST AFRICA THIS MORNING. 850 MB RELATIVE VORTICITY
FIELDS ALSO SHOW MAXIMUM VALUES ALONG THE WAVE AXIS NEAR
14N...AND IN ASSOCIATION WITH A NORTHERN VORTEX ANALYZED AS A
1011 MB LOW CENTERED NEAR THE NORTHERN TIP OF THE DEPICTED WAVE
AXIS. ISOLATED MODERATE CONVECTION IS FROM 08N-12N BETWEEN 18W-
22W.

TROPICAL WAVE EXTENDS FROM 07N46W TO 17N43W MOVING W AT 20 KT.
THE WAVE COINCIDES WITH A GLOBAL MODEL INDICATED 700 MB
TROUGHING THAT MATCHES UP WELL WITH TOTAL PRECIPITABLE WATER
IMAGERY AND LOW-LEVEL SATELLITE DERIVED WINDS. IT IS LIKELY
ENERGY FROM THE WAVE IMPACTED THE DEVELOPMENT OF A 1009 MB NOW
CENTERED TO THE EAST OF THE WAVE NEAR 11N38W. ISOLATED MODERATE
CONVECTION IS FROM 10N-12N BETWEEN 41W-44W.

TROPICAL WAVE EXTENDS FROM 09N78W TO 18N79W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH BROAD GLOBAL MODEL INDICATED 700 MB
TROUGHING ACROSS THE WESTERN CARIBBEAN SEA AND MOST RELATIVE
VORTICITY AT 850 MB REMAINING S OF 13N BETWEEN 76W-80W.
SCATTERED MODERATE CONVECTION IS CONFINED S OF 10N BETWEEN 76W-
84W...AND LIKELY MORE ASSOCIATED WITH THE CLOSE PROXIMITY TO THE
MONSOON TROUGH AXIS.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N16W TO
10N20W TO 10N24W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
EXTENDS FROM 10N24W TO 12N34W TO 11N38W...THEN RESUMES NEAR
07N47W TO 06N57W. ASIDE FROM CONVECTION ASSOCIATED WITH THE
TROPICAL WAVE ALONG 45W...WIDELY SCATTERED MODERATE CONVECTION
IS FROM 04N-13N BETWEEN 23W-41W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL NORTHEAST TO EASTERLY FLOW IS OCCURRING OVER MUCH OF
THE GULF ON THE SOUTHEASTERN PERIPHERY OF A MIDDLE TO UPPER
LEVEL RIDGE ANCHORED OVER THE NW GULF WATERS AND WEST TEXAS.
DEBRIS MOISTURE AND CLOUDINESS CONTINUES TO SPREAD SOUTHWESTWARD
FROM ACTIVE CONVECTION OCCURRING ACROSS THE NE GULF. THE AREA OF
CONVECTION STEMS FROM A BROAD AREA LOWER PRESSURE FOCUSED ON A
WEAK 1013 MB LOW CENTERED IN THE FLORIDA BIG BEND REGION NEAR
30N83W. LOW-LEVEL MOISTURE CONVERGENCE ALONG WITH FAVORABLE
MIDDLE TO UPPER LEVEL DIFFLUENCE IS GENERATING SCATTERED SHOWERS
AND TSTMS FROM 26N-30N BETWEEN 82W-89W. OTHERWISE...THE
REMAINDER OF THE BASIN IS UNDER THE INFLUENCE OF SURFACE RIDGING
ANCHORED BY A 1018 MB HIGH CENTERED NEAR 25N86W. A RIDGE AXIS
EXTENDS NW FROM THE HIGH TO THE LOUISIANA COAST AND EAST ALONG
25N INTO THE SW NORTH ATLC. GENERALLY MODERATE TO OCCASIONAL
FRESH ANTICYCLONIC WINDS PREVAIL ON THE PERIPHERY OF THE RIDGE
WITH LIGHTER WINDS OCCURRING WITHIN 120 NM OF THE HIGH CENTER.
THE RIDGE IS FORECAST TO REMAIN NEARLY STATIONARY AND ANCHORED
ACROSS THE EAST-CENTRAL GULF WATERS THROUGH LATE SATURDAY.

CARIBBEAN SEA...
GENERALLY NORTHERLY FLOW ALOFT IS NOTED ON WATER VAPOR IMAGERY W
OF 76W ON THE WESTERN PERIPHERY OF UPPER LEVEL TROUGHING
STEMMING FROM AN UPPER LEVEL LOW CENTERED NE OF PUERTO RICO NEAR
22N61W. MOSTLY FAIR SKIES ARE NOTED ACROSS THE WESTERN CARIBBEAN
EVEN AS A TROPICAL WAVE ALONG 79W CONTINUES WESTWARD. SCATTERED
SHOWERS AND TSTMS REMAIN CONFINED S OF 10N BETWEEN 76W-
84W...INCLUDING PORTIONS OF PANAMA AND COSTA RICA. A FEW
ISOLATED SHOWERS AND TSTMS ARE ALSO OCCURRING IN THE ADJACENT
COASTAL WATERS BETWEEN EASTERN CUBA AND JAMAICA. FARTHER
EAST...ON THE SOUTHERN PERIPHERY OF THE TROUGHING AND UPPER
LEVEL LOW...WEST-SOUTHWESTERLY FLOW ALOFT PREVAILS UNDER MOSTLY
FAIR SKIES...HOWEVER A FEW ISOLATED SHOWERS ARE BEGINNING TO
INITIATE ACROSS HISPANIOLA AND THE ADJACENT COASTAL WATERS N OF
16N. FINALLY...FRESH TO STRONG TRADES CONTINUE ACROSS CENTRAL
PORTIONS DUE TO A STRENGTHENED PRESSURE GRADIENT. THESE WINDS
ARE EXPECTED TO PERSIST THROUGH THE UPCOMING WEEKEND GENERALLY
BETWEEN 70W-80W.

...HISPANIOLA...
CURRENTLY...ISOLATED SHOWERS AND TSTMS ARE BEGINNING TO INITIATE
ACROSS THE ISLAND DUE TO NEAR-PEAK DAYTIME HEATING AND
INSTABILITY. IT IS LIKELY CONVECTIVE AREAL COVERAGE WILL
GRADUALLY INCREASE THROUGH THE EARLY EVENING AND THE BEGIN TO
DIMINISH THROUGH THE EARLY OVERNIGHT HOURS. WITH A MARGINALLY
DIFFLUENT ENVIRONMENT ALOFT ACROSS THE ISLAND...THIS OVERALL
SYNOPTIC REGIME IS EXPECTED TO PERSIST AND GENERATE CONVECTION
DURING THE EARLY AFTERNOON AND LATE EVENING THE NEXT FEW DAYS.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR IMAGERY WITH AXIS
EXTENDING FROM 37N67W TO A BASE NEAR 30N71W. THIS SHORTWAVE
TROUGH SUPPORTS A COLD FRONT ANALYZED NORTH OF THE DISCUSSION
AREA FROM 35N66W TO 32N76W AND BECOMES STATIONARY TO 31N80W. LOW-
LEVEL MOISTURE CONVERGENCE SOUTH OF THE FRONT COUPLED WITH
MAXIMUM MIDDLE TO UPPER LEVEL DIFFLUENCE IS GENERATING SCATTERED
SHOWERS AND ISOLATED TSTMS ACROSS MUCH OF THE SW NORTH ATLC FROM
26N-33N BETWEEN 66W-79W. TO THE SOUTHEAST OF THE FRONT...AN
UPPER LEVEL LOW IS CENTERED NEAR 22N61W AND IS GENERATING AN
AREA OF ISOLATED SHOWERS AND TSTMS FROM 21N-27N BETWEEN 54W-63W
ON THE SOUTHERN PERIPHERY OF A SURFACE RIDGE ANCHORED BY A 1022
MB HIGH CENTERED NEAR 29N63W. FARTHER EAST...THE REMAINDER OF
THE EASTERN ATLC IS UNDER THE INFLUENCE OF ANOTHER SURFACE RIDGE
ANCHORED BY A 1023 MB HIGH CENTERED NEAR 32N28W. A WEAKNESS
BETWEEN THE TWO AFOREMENTIONED HIGHS IS ANALYZED AS A SURFACE
TROUGH FROM 31N44W TO 25N54W. POSSIBLE ISOLATED SHOWERS ARE
OCCURRING WITHIN 45 NM EITHER SIDE OF THE BOUNDARY.

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

$$
HUFFMAN
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