[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181750
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU JUL 18 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 09N35W TO 20N32W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH AN AMPLIFIED GLOBAL MODEL INDICATED
700 MB TROUGH AXIS ALONG 34W AND MATCHING TOTAL PRECIPITABLE
WATER IMAGERY MAXIMUM FROM 08N-20N BETWEEN 24W-34W...PRIMARILY
TO THE EAST OF THE WAVE AXIS. NO SIGNIFICANT DEEP CONVECTION
ASSOCIATED THE WAVE AT THIS TIME DUE TO THE STABLING EFFECT OF
THE SAHARAN AIR LAYER ACROSS THE EASTERN ATLC.

TROPICAL WAVE EXTENDS FROM 11N69W TO 20N66W MOVING W AT 20-25
KT. THE WAVE IS ASSOCIATED WITH BROAD LOWER LEVEL TROUGHING
ACROSS THE EASTERN CARIBBEAN WITH TOTAL PRECIPITABLE WATER
IMAGERY INDICATING A MAXIMUM FROM 14N-22N BETWEEN 61W-
70W...STRETCHING TO THE NE OVER PORTIONS OF THE CENTRAL ATLC.
SCATTERED MODERATE CONVECTION HAS SUSTAINED ITSELF OVER THE PAST
24 TO 36 HOURS AND CONTINUES FROM 17N-22N BETWEEN 62W-69W...WITH
WIDELY SCATTERED SHOWERS COVERING A LARGER AREA FROM 14N-22N
BETWEEN 61W-72W.

TROPICAL WAVE EXTENDS FROM 07N79W TO 14N77W MOVING W AT 15-20
KT. THE WAVE CONTINUES TO PROGRESS ACROSS THE SW CARIBBEAN SEA
BENEATH NORTHERLY FLOW ALOFT...WHICH IS LIMITING SIGNIFICANT
DEEP CONVECTION TO AN AREA S OF 10N...HOWEVER THE WAVE COINCIDES
WITH A WEAK 700 MB TROUGH AND AREA OF MAXIMUM VORTICITY IN THE
VICINITY OF 11N78W. THE WAVE IS EXPECTED TO CROSS PORTIONS OF
CENTRAL AMERICA THIS AFTERNOON INTO EARLY FRIDAY AND EMERGE INTO
THE EASTERN PACIFIC REGION THEREAFTER. SCATTERED MODERATE AND
ISOLATED STRONG CONVECTION STRATTLES PANAMA FROM 04N-10N BETWEEN
76W-81W.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 11N16W TO
10N22W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
10N22W TO 12N30W TO 07N38W TO 04N51W. ISOLATED MODERATE
CONVECTION IS FROM 06N-12N BETWEEN 12W-19W. WIDELY SCATTERED
MODERATE CONVECTION IS FROM 04N-10N BETWEEN 35W-59W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES A UPPER LEVEL LOW IS CENTERED OVER
THE NORTH-CENTRAL GULF NEAR 28N89W THAT CONTINUES TO CREATE LIFT
AND ADVECT MOISTURE OVER PORTIONS OF THE EASTERN GULF AND
FLORIDA PENINSULA...AS WELL AS PORTIONS OF THE WESTERN GULF THIS
AFTERNOON. MUCH OF THE PRECIPITATION AND CONVECTION IS FOCUSED
ALONG A PAIR OF SURFACE TROUGHS...ONE ANALYZED ACROSS THE
SOUTHERN FLORIDA PENINSULA TO 27N82W TO 23N90W...AND THE OTHER
ANALYZED FROM ACROSS SOUTHERN TEXAS NEAR 28N98W TO 21N95W.
SCATTERED SHOWERS AND TSTMS ARE OCCURRING FROM 23N-28N BETWEEN
81W-88W WITH THE EASTERN-MOST SURFACE TROUGH AND FROM 24N-28N
BETWEEN 92W-98W WITH THE WESTERN-MOST SURFACE TROUGH. THE
TROUGHING ACROSS THE FLORIDA PENINSULA AND SE GULF WILL CONTINUE
TO DRIFT SLOWLY WEST-NORTHWESTWARD DURING THE NEXT COUPLE OF
DAYS EVENTUALLY DISSIPATING ALONG THE LOUISIANA AND TEXAS GULF
COAST IN THE NW GULF EARLY SATURDAY. THEREAFTER...SURFACE
RIDGING ANCHORED IN THE SW NORTH ATLC WILL EXTEND WESTWARD AND
ONCE AGAIN RE-ESTABLISH SE TO S WINDS ACROSS THE BASIN OVER THE
WEEKEND.

CARIBBEAN SEA...
A WEAK UPPER LEVEL LOW IS CENTERED OVER THE SE CARIBBEAN NEAR
15N66W WITH CYCLONIC FLOW REACHING AS FAR NORTH AS 20N BETWEEN
61W-72W. UPPER LEVEL DIFFLUENCE IS ASSOCIATED WITH THE TROUGHING
ON ITS NORTHERN PERIPHERY...AND WITH THE PRESENCE OF A TROPICAL
WAVE...ANALYZED FROM NORTH OF PUERTO RICO NEAR 20N66W TO CURACAO
NEAR 12N69W...INCREASED MOISTURE AND CLOUDINESS ALONG WITH
SCATTERED SHOWERS AND TSTMS ARE NOTED ON SATELLITE IMAGERY FROM
15N-22N BETWEEN 61W-72W. THIS TROPICAL WAVE IS FORECAST TO
CONTINUE WESTWARD AND INCREASE PRECIPITATION CHANCES FOR JAMAICA
AND HISPANIOLA OVER THE WEEKEND. ANOTHER TROPICAL WAVE IS
ANALYZED ACROSS THE SW CARIBBEAN ALONG 79W AND CONTINUES MOVING
BENEATH NORTHERLY 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 ACROSS THE SW
CARIBBEAN S OF 13N WITH SCATTERED SHOWERS AND TSTMS OCCURRING
BETWEEN 76W-84W. THIS CONVECTION IS ALSO LIKELY ENHANCED DUE TO
CLOSE PROXIMITY OF THE MONSOON TROUGH ALONG 09N/10N ACROSS
WESTERN PANAMA AND COSTA RICA. FINALLY...WIDELY SCATTERED
SHOWERS AND ISOLATED TSTMS ARE OCCURRING OVER THE NW CARIBBEAN N
OF 16N BETWEEN 81W-88W. THE CONVECTION IS OCCURRING WITHIN AN
AREA OF MAXIMUM MIDDLE TO UPPER LEVEL DIFFLUENCE SOUTH OF AN
UPPER LEVEL LOW CENTERED OVER THE NORTH-CENTRAL GULF OF MEXICO.

HISPANIOLA...
MOISTURE CONTINUES TO INCREASE ACROSS THE ISLAND THIS AFTERNOON
AS A TROPICAL WAVE CURRENTLY ANALYZED ACROSS PUERTO RICO
CONTINUES MOVING WESTWARD. LOW-LEVEL MOISTURE CONVERGENCE ABOUT
THE WAVE AXIS AND UPPER LEVEL DIFFLUENCE MAXIMIZED ON THE
NORTHERN PERIPHERY OF AN UPPER LEVEL LOW CENTERED OVER THE SE
CARIBBEAN IS GENERATING SCATTERED SHOWERS AND TSTMS FROM 16N-22N
BETWEEN 62W-72W. THE STRONGEST OF THIS ACTIVITY CURRENTLY IS
ACROSS AND IMMEDIATELY NORTH OF PUERTO RICO. AS THIS AREA OF
PRECIPITATION AND CONVECTION MOVES WESTWARD OVER THE NEXT 24 TO
36 HOURS...HEAVY RAINFALL AND A HIGH POTENTIAL FOR LOCALIZED
FLOODING IS POSSIBLE.

ATLANTIC OCEAN...
AN UPPER LEVEL LOW IS CENTERED OVER THE NORTH-CENTRAL GULF OF
MEXICO NEAR 28N89W THAT SUPPORTS A SURFACE TROUGH ANALYZED FROM
OFF THE EASTERN COAST OF THE FLORIDA PENINSULA NEAR 29N79W
TO27N82W AND INTO THE SE GULF OF MEXICO. LOW-LEVEL MOISTURE
CONVERGENCE ALONG WITH MIDDLE TO UPPER LEVEL DIFFLUENCE
ASSOCIATED WITH THE TROUGHING AND UPPER LEVEL LOW IS GENERATING
SCATTERED SHOWERS AND TSTMS FROM 23N-30N BETWEEN 75W-82W...
INCLUDING THE BAHAMAS AND MUCH OF THE FLORIDA PENINSULA. FARTHER
EAST...A COMPLEX AREA OF UPPER LEVEL TROUGHING EXTENDS FROM
27N55W TO 26N71W THAT IS GENERATING ISOLATED SHOWERS AND TSTMS
FROM 23N-27N BETWEEN 67W-75W. OTHERWISE...THE REMAINDER OF THE
CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE
RIDGE ANCHORED BY A PAIR OF 1025 MB HIGHS CENTERED NEAR 27N49W
AND 28N57W. ANOTHER HIGH IS CENTERED BETWEEN THE AZORES AND
MADEIRA ISLANDS NEAR 34N20W AS A 1025 MB HIGH. SATELLITE IMAGERY
INDICATES THE SAHARAN AIR LAYER CONTINUES TO IMPACT MUCH OF THE
EASTERN AND CENTRAL ATLC GENERALLY N OF 12N E OF 60W.

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

$$
HUFFMAN


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