[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171750
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED JUL 17 2013

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 10N26W TO 19N22W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH A HIGHLY AMPLIFIED GLOBAL MODEL
INDICATED 700 MB TROUGH AXIS ALONG 25W AND MATCHING TOTAL
PRECIPITABLE WATER IMAGERY SHOWS A MAXIMUM FROM 07N-19N BETWEEN
16W-25W...PRIMARILY TO THE EAST OF THE WAVE AXIS. WIDELY
SCATTERED MODERATE CONVECTION IS FROM 07N-14N BETWEEN 18W-28W.

TROPICAL WAVE EXTENDS FROM 12N60W TO 22N58W MOVING W AT 20-25
KT. THE WAVE...WHICH OVER THE PAST SEVERAL DAYS HAS CONTINUED TO
BE INFLUENCED BY AN EXTENSIVE SAHARAN AIR LAYER...IS BEGINNING
TO EMERGE FROM THAT INFLUENCE AND EXHIBIT A BIT MORE CONVECTIVE
ACTIVITY AS IT APPROACHES THE LESSER ANTILLES AND EASTERN
CARIBBEAN SEA THIS AFTERNOON INTO THURSDAY. SCATTERED MODERATE
CONVECTION IS FROM 15N-19N BETWEEN 54W-60W...WITH WIDELY
SCATTERED SHOWERS COVERING A LARGER AREA FROM 12N-20N BETWEEN
53W-65W.

TROPICAL WAVE EXTENDS FROM 12N75W TO 19N72W MOVING W AT 20 KT.
THE WAVE CONTINUES TO PROGRESS SWIFTLY ACROSS THE CARIBBEAN SEA
BENEATH ANTICYCLONIC FLOW ALOFT...WHICH IS LIMITING ANY
SIGNIFICANT DEEP CONVECTION AT THIS TIME...HOWEVER THE WAVE
COINCIDES WITH A WEAK 700 MB TROUGH AND THE ENERGY ASSOCIATED
WITH THE WAVE ON THE SOUTHERN EXTENT IS EXPECTED TO CROSS
CENTRAL AMERICA AND EMERGE INTO THE EASTERN PACIFIC REGION BY
EARLY FRIDAY. A FEW ISOLATED SHOWERS AND TSTMS ARE OCCURRING
ACROSS EASTERN HISPANIOLA IN AN AREA OF LOW-LEVEL MOISTURE
CONVERGENCE.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 20N17W TO
19N21W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
10N27W TO 02N46W. ASIDE FROM CONVECTION ASSOCIATED WITH THE
TROPICAL WAVE ALONG 25W...WIDELY SCATTERED MODERATE CONVECTION
IS FROM 05N-09N BETWEEN 27W-39W...AND FROM 02N-10N BETWEEN 39W-
50W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES A UPPER LEVEL LOW IS CENTERED OVER
THE EASTERN GULF NEAR 27N84W THAT CONTINUES TO CREATE LIFT AND
ADVECT MOISTURE OVER PORTIONS OF THE SW NORTH ATLC...THE FLORIDA
PENINSULA...FLORIDA STRAITS...AND SE GULF THIS AFTERNOON. MUCH
OF THE PRECIPITATION AND CONVECTION IS FOCUSED ALONG A SURFACE
TROUGH ALONG THE EASTERN FLORIDA PENINSULA WITH SCATTERED
SHOWERS AND TSTMS OCCURRING FROM 23N-27N BETWEEN 79W-87W.
FARTHER WEST...NORTHERLY FLOW ALOFT DOMINATES W OF 90W WITH AN
OVERALL WEAK SURFACE PRESSURE GRADIENT AND GENERALLY E-SE WINDS
IN THE RANGE OF 10 TO 20 KT. MOSAIC DOPPLER RADAR IMAGERY AND
LIGHTNING DATA INDICATE SCATTERED SHOWERS AND ISOLATED TSTMS ARE
OCCURRING OVER THE NW GULF N OF 25N W OF 90W...AND S OF 25N W OF
94W. THE CURRENT TROUGHING ACROSS THE FLORIDA PENINSULA WILL
CONTINUE TO SLOWLY DRIFT WESTWARD DURING THE NEXT COUPLE OF DAYS
EVENTUALLY SWINGING NORTHWESTWARD AND INLANDN ACROSS THE
LOUISIANA AND TEXAS GULF COAST LATE FRIDAY. THEREAFTER...SURFACE
RIDGING ANCHORED IN THE SW NORTH ATLC WILL EXTEND WESTWARD AND
ONCE AGAIN RE-ESTABLISH E-SE WINDS ACROSS THE BASIN OVER THE
WEEKEND.

CARIBBEAN SEA...
A WEAK UPPER LEVEL RIDGE AXIS EXTENDS FROM THE SOUTH-CENTRAL
CARIBBEAN NEAR 12N69W NE INTO THE CENTRAL ATLC NEAR 19N54W.
MARGINAL UPPER LEVEL DIFFLUENCE IS ASSOCIATED WITH THIS
RIDGE...AND WITH THE PRESENCE OF A TROPICAL WAVE APPROACHING THE
LESSER ANTILLES AND EASTERN CARIBBEAN...INCREASED MOISTURE AND
PRECIPITATION IS EXPECTED OVER THE NEXT 24 TO 36 HOURS ACROSS
THE ISLAND CHAIN. SCATTERED SHOWERS AND TSTMS ARE CURRENTLY EAST
OF THE BASIN FROM 15N-19N BETWEEN 55W-61W...WITH ISOLATED
SHOWERS ELSEWHERE FROM 13N-19N E OF 64W. THIS TROPICAL WAVE IS
FORECAST TO CONTINUE WESTWARD AND INCREASE PRECIPITATION CHANCES
FOR PUERTO RICO AND HISPANIOLA OVER THE WEEKEND. ANOTHER
TROPICAL WAVE IS CURRENTLY ALONG 74W AND CONTINUES MOVING
BENEATH STABLE ANTICYCLONIC FLOW ALOFT AT THIS TIME. ENERGY
ASSOCIATED WITH THE WAVE IS EXPECTED TO CROSS CENTRAL AMERICA
OVER THE WEEKEND AND EMERGE INTO THE OPEN WATERS OF THE EASTERN
PACIFIC. LOW-LEVEL MOISTURE CONVERGENCE REMAINS MAXIMIZED WEST
OF THE TROPICAL WAVE ACROSS THE SW CARIBBEAN EXTENDING ALONG THE
COAST OF NICARAGUA TO WESTERN PANAMA. SCATTERED SHOWERS AND
TSTMS ARE OCCURRING WITHIN 120 NM EITHER SIDE OF A LINE FROM
13N84W TO 09N77W. THIS CONVECTION IS ALSO LIKELY ENHANCED DUE TO
CLOSE PROXIMITY OF THE MONSOON TROUGH ALONG 08N/09N BETWEEN
NORTHERN COLOMBIA AND SOUTHERN COSTA RICA. FINALLY...WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING OVER THE NW
CARIBBEAN N OF 18N BETWEEN 79W-87W. THE CONVECTION IS OCCURRING
WITHIN AN AREA OF MAXIMUM MIDDLE TO UPPER LEVEL DIFFLUENCE SOUTH
OF AN UPPER LEVEL LOW CENTERED OVER THE EASTERN GULF OF MEXICO.

HISPANIOLA...
CURRENTLY A FEW ISOLATED SHOWERS AND TSTMS ARE OCCURRING ACROSS
THE DOMINICAN REPUBLIC AS A TROPICAL WAVE IN THE VICINITY OF THE
ISLAND CONTINUES TO MOVE WESTWARD. AFTERNOON AND EARLY EVENING
SHOWERS AND TSTMS ARE EXPECTED DUE TO PEAK DAYTIME HEATING AND
INSTABILITY AND WILL LIKELY DIMINISH BY LATE EVENING.
SYNOPICALLY OVER THE NEXT 24 TO 48 HOURS...THE NEXT TROPICAL
WAVE...CURRENTLY EAST OF THE LESSER ANTILLES...WILL BEGIN TO
IMPACT HISPANIOLA INCREASING MOISTURE AND CLOUDINESS BY EARLY
THURSDAY INTO FRIDAY WITH SCATTERED SHOWERS AND TSTMS POSSIBLE.

ATLANTIC OCEAN... AN UPPER LEVEL LOW IS CENTERED OVER THE
EASTERN GULF OF MEXICO NEAR 27N84W THAT SUPPORTS A SURFACE
TROUGH ANALYZED ALONG THE EASTERN COAST OF THE FLORIDA
PENINSULA. LOW-LEVEL MOISTURE CONVERGENCE ALONG WITH MIDDLE TO
UPPER LEVEL DIFFLUENCE IS GENERATING SCATTERED SHOWERS AND TSTMS
ACROSS A LARGE PORTION OF THE SW NORTH ATLC FROM 22N-28N BETWEEN
75W-82W...INCLUDING THE BAHAMAS AND MUCH OF THE SOUTHERN FLORIDA
PENINSULA. FARTHER EAST...ANOTHER WEAKER UPPER LEVEL LOW IS
CENTERED NEAR 28N70W THAT SUPPORTS A SURFACE TROUGH FROM 26N70W
TO 30N68W. SCATTERER SHOWERS AND ISOLATED TSTMS ARE OCCURRING
FROM 26N-30N BETWEEN 67W-69W. OTHERWISE...THE REMAINDER OF THE
CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE
RIDGE ANCHORED BY A 1025 MB HIGH CENTERED NEAR 27N46W. THE
SAHARAN AIR LAYER CONTINUES TO IMPACT MUCH OF THE EASTERN ATLC
WITH SUSPENDED DUST NOTED ON VISIBLE SATELLITE IMAGERY GENERALLY
N OF 10N E OF 53W.

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

$$
HUFFMAN


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