[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211746
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE JUL 21 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 09N26W TO 18N23W MOVING W AT 20 KT.
THE WAVE COINCIDES WITH A VERY BROAD AND SUBTLE 700 MB TROUGH
NOTED IN GLOBAL MODEL GUIDANCE BETWEEN 18W-28W. A NARROW AND
WEAK AREA OF 850 MB RELATIVE VORTICITY ALSO EXTENDS ACROSS THE
WAVE AXIS FROM 13N23W TO 10N30W INDICATING THE STRETCHED OUT
NATURE OF THE ENERGY ASSOCIATED WITH THE WAVE. NO SIGNIFICANT
DEEP CONVECTION IS OCCURRING WITH THE WAVE AT THIS TIME DUE TO
SAHARAN DUST COVERING MUCH OF THE EASTERN TROPICAL ATLC.

TROPICAL WAVE EXTENDS FROM 09N59W TO 18N55W MOVING W AT 20 KT.
THE WAVE COINCIDES WITH 700 MB TROUGHING ALOFT BETWEEN 54W-61W
ON THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL RIDGE CENTERED OVER
THE CENTRAL ATLC NEAR 23N51W. SCATTERED MODERATE CONVECTION IS
OCCURRING WITHIN 90 NM EITHER SIDE OF A LINE FROM 07N54W TO
11N64W...INCLUDING TRINIDAD AND TOBAGO...AND COASTAL NE
VENEZUELA.

TROPICAL WAVE EXTENDS FROM 08N69W TO 18N66W MOVING W AT 20 KT.
THE WAVE REMAINS EMBEDDED WITHIN A NARROW MAXIMUM OF TOTAL
PRECIPITABLE WATER BETWEEN 64W-69W THAT STRETCHES NORTH-
NORTHEASTWARD FOCUSED ALONG A SURFACE TROUGH EXTENDING FROM
19N66W TO 24N61W. THE MOISTURE THEN EXTENDS INTO THE INFLUENCE
OF AN UPPER LEVEL TROUGH AXIS EXTENDING OVER THE CENTRAL ATLC.
ISOLATED MODERATE CONVECTION IS FROM 05N-10N BETWEEN 64W-71W
ACROSS PORTIONS OF CENTRAL AND NW VENEZUELA. ISOLATED SHOWERS
ARE OCCURRING ACROSS THE EASTERN CARIBBEAN S OF 16N BETWEEN 65W-
71W.

TROPICAL WAVE EXTENDS FROM 07N76W TO 17N74W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH BROAD 700 MB TROUGHING BETWEEN 72W-
79W AND IS LARGELY INFLUENCED ALOFT BY AN UPPER LEVEL RIDGE
CENTERED OVER THE SW CARIBBEAN NEAR 14N82W. ISOLATED MODERATE
CONVECTION IS FROM 06N-11N BETWEEN 75W-80W.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM THE AFRICAN COAST NEAR
14N17W TO 10N22W TO 06N34W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 06N34W TO 05N42W TO 07N53W.

...DISCUSSION...

GULF OF MEXICO...
NORTHEAST TO EASTERLY FLOW ALOFT PREVAILS OVER MUCH OF THE GULF
THIS AFTERNOON BETWEEN A MIDDLE TO UPPER LEVEL ANTICYCLONIC
CIRCULATION CENTERED OVER CENTRAL TEXAS AND AN UPPER LEVEL LOW
CENTERED OVER THE NORTHERN YUCATAN PENINSULA. WHILE A MAJORITY
OF THE BASIN IS UNDER THIS RELATIVELY STABLE FLOW...AT THE
SURFACE...WEAK TROUGHING AND LOW-LEVEL MOISTURE CONVERGENCE IS
PRESENT ACROSS THE NE GULF STEMMING FROM A WEAK STREAM OF 500 MB
RELATIVE VORTICITY EXTENDING FROM OVER THE FLORIDA BIG BEND
REGION SW TO OVER THE NW GULF NEAR 27N93W. THIS MID-LEVEL
VORTICITY IS PROVIDING FOCUS FOR SCATTERED SHOWERS AND TSTMS
OCCURRING FROM 25N-29N BETWEEN 83W-90W. OTHERWISE...A SURFACE
RIDGE AXIS EXTENDS FROM THE SW NORTH ATLC ALONG 25N TO 90W THEN
TO THE EAST-CENTRAL MEXICO COAST NEAR TUXPAN. GENTLE TO
OCCASIONAL MODERATE BREEZE ANTICYCLONIC FLOW IS FORECAST ACROSS
THE BASIN THROUGH LATE THURSDAY.

CARIBBEAN SEA...
THE MAIN IMPACT FOR THE CARIBBEAN BASIN THIS AFTERNOON IS THREE
TROPICAL WAVE MOVING WESTWARD. WHILE THOSE ARE DETAILED
ABOVE...WATER VAPOR IMAGERY INDICATES THAT MOST OF THE MOISTURE
IS FOUND E OF 70W AS DRY AIR ALOFT REMAINS IN PLACE OVER THE
WESTERN CARIBBEAN IN ASSOCIATION WITH AN UPPER LEVEL RIDGE
ANCHORED NEAR 14N81W. FARTHER EAST...MOISTURE AND CLOUDINESS
INCREASES WITH LOW-LEVEL MOISTURE CONVERGENCE OCCURRING ALONG A
LINE EXTENDING FROM 10N60W SE OF TRINIDAD AND TOBAGO TO THE ABC
ISLANDS NEAR 13N70W. WIDELY SCATTERED SHOWERS AND TSTMS ARE
OCCURRING WITHIN 90 NM OF THIS AREA...WITH ISOLATED SHOWERS AND
TSTMS OCCURRING ELSEWHERE GENERALLY E OF 70W. FINALLY...MODERATE
TO FRESH BREEZE CONDITIONS ARE EXPECTED TO PERSIST THROUGH LATE
THURSDAY WHEN THEREAFTER THE PRESSURE GRADIENT ACROSS THE SOUTH-
CENTRAL PORTION OF THE BASIN WILL STRENGTHEN INCREASING E-NE
WINDS S OF 15N BETWEEN 69W-80W FRIDAY INTO THE UPCOMING WEEKEND.

...HISPANIOLA...
CURRENTLY...MOSTLY CLEAR SKIES PREVAIL...HOWEVER WITH THE
APPROACH OF A TROPICAL WAVE ALONG 68W...HIGHER PROBABILITY OF
SCATTERED SHOWERS AND TSTMS IS LIKELY THROUGH LATE THURSDAY INTO
FRIDAY.

ATLANTIC OCEAN...
NORTH-NORTHEASTERLY FLOW ALOFT PREVAILS OVER MUCH OF THE SW
NORTH ATLC BETWEEN AN UPPER LEVEL ANTICYCLONE CENTERED NEAR
31N78W AND AN UPPER LEVEL LOW CENTERED NEAR 23N63W. WHILE
OVERALL CONDITIONS REMAIN STABLE ACROSS THE SW NORTH ATLC WITHIN
A SURFACE RIDGE WITH AXIS ALONG 25N/26N...LOW-LEVEL MOISTURE
CONVERGENCE IS MAXIMIZED ALONG A LINE FROM 26N79W TO 31N77W IN
WHICH ISOLATED SHOWERS AND TSTMS ARE OCCURRING WITHIN 60 NM
EITHER SIDE OF THE LINE. FARTHER EAST...WITHIN THE INFLUENCE OF
THE UPPER LEVEL LOW...A SURFACE TROUGH...THE NORTHERN PIECE OF
ENERGY FRACTURED AWAY FROM THE TROPICAL WAVE ALONG 68W...IS
GENERATING SCATTERED SHOWERS AND TSTMS FROM 20N-24N BETWEEN 62W-
67W...AND WITHIN 90 NM OF THE POINT 26N58W. OTHERWISE...A NEARLY
STATIONARY RIDGE ANCHORED BY A 1023 MB HIGH CENTERED NEAR 29N46W
INFLUENCES THE REMAINDER OF THE CENTRAL AND EASTERN ATLC.

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

$$
HUFFMAN
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