000 AXNT20 KNHC 091147 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT TUE JUL 09 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURES... AS OF 1200 UTC...TROPICAL STORM CHANTAL IS CENTERED NEAR 13.8N 59.7W...OR ABOUT 39 NM N-NW OF BARBADOS AND ABOUT 74 NM E OF ST. LUCIA MOVING W-NW NEAR 22 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1010 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT3/WTNT33 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. ON THE CURRENT TRACK...CHANTAL IS MOVE THROUGH THE LESSER ANTILLES LATER LATER TODAY AND BE SOUTH OF PUERTO RICO WEDNESDAY MORNING. TOTAL RAIN ACCUMULATIONS OF 2-4 INCHES ARE EXPECTED WITH MAXIMUM OF 6 INCHES POSSIBLE. CURRENTLY SCATTERED MODERATE/STRONG CONVECTION IS FROM 11N-15N BETWEEN 55W- 61W. SOME OF THIS ACTIVITY IS ALREADY IMPACTING THE WINDWARD ISLANDS. ...TROPICAL WAVES... TROPICAL WAVE IS JUST OFF THE COAST OF AFRICA FROM 18N17W TO 9N18W MOVING WEST AT 5 KT. THE WAVE ALIGNS WITH A MAXIMUM MOISTURE SIGNAL IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 7N-12N BETWEEN 14W- 23W. TROPICAL WAVE IS ALONG 11N34W TO 5N34W MOVING WEST NEAR 10-15 KT. THE WAVE WAS RELOCATED FARTHER WEST NEAR AN AREA OF STRONG CONVECTION. THE WAVE ALIGNS WITH A LOW-AMPLITUDE 700 MB TROUGH. SCATTERED MODERATE/STRONG CONVECTION IS FROM 5N-7N BETWEEN 32W- 41W. TROPICAL WAVE IS ALONG 23N82W TO 13N83W MOVING WEST AT 15-20 KT. THE NORTHERN PORTION OF THIS WAVE HAS BROKEN OFF AND IS BEING ANALYZED AS A SURFACE TROUGH. THE WAVE IS ON THE WEST SIDE OF A LARGE AREA OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. ISOLATED MODERATE CONVECTION IS FROM 14N-16N BETWEEN 81W-83W. A CLUSTER OF MODERATE/STRONG CONVECTION IS FARTHER SOUTH FROM 10N-12N BETWEEN 81W-84W...BUT MAY BE MORE ASSOCIATED WITH THE MONSOON TROUGH. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE COAST OF GUINEA-BISSAU NEAR 12N17W AND CONTINUES ALONG 8N27W 5N37W. THERE IS NOT AN ITCZ AXIS AT THIS TIME. BESIDES CONVECTION NEAR THE TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS FROM 4N-10N BETWEEN 23W- 30W. ...DISCUSSION... GULF OF MEXICO... WEAK SURFACE RIDGING IS PRESENT OVER THE GULF OF MEXICO EXTENDING FROM HIGH PRESSURE OVER THE EASTERN CONUS AND WEST ATLC. THE AREA IS RELATIVELY CLEAR COMPARED TO THE LAST FEW DAYS ...BUT TOTAL PRECIPITABLE WATER IMAGERY CONTINUES TO SHOW INCREASED MOISTURE OVER THE WESTERN HALF OF THE BASIN. EAST TO SOUTHEAST WIND OF 10-15 KT ARE THROUGHOUT THE AREA. A FEW ISOLATED SHOWERS/THUNDERSTORMS ARE OFF THE NW COAST OF FLORIDA AS WELL AS OVER THE NW GULF FROM 25N-29N BETWEEN 90W-95W. ALOFT...PRIMARILY NE FLOW COVERS THE BASIN. WEAK RIDGING WILL REMAIN THE DOMINANT FEATURE THROUGHOUT THE GULF EXCEPT FOR A SURFACE TROUGH OVER THE BAHAMAS WHICH IS EXPECTED TO DRIFT WEST OVER FLORIDA. CARIBBEAN SEA... MUCH OF THE CARIBBEAN IS EXPERIENCING FAIR CONDITIONS DESPITE THE PRESENCE OF A TROPICAL WAVE EXTENDING FROM WESTERN CUBA TO HONDURAS. A FEW ISOLATED SHOWERS/THUNDERSTORMS ARE WEST OF JAMAICA AND OFF THE COAST OF NICARAGUA NEAR THE WAVE. SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO SOUTH OF THE DOMINICAN REPUBLIC. A CLUSTER OF STRONGER SHOWERS/THUNDERSTORMS IS OFF THE COAST OF COSTA RICA LINKED TO THE MONSOON TROUGH THAT EXTENDS ALONG 10N TO NORTHERN COLOMBIA. TRADEWIND FLOW OF MOSTLY 20 KT IS THROUGHOUT THE AREA. ALOFT...UPPER TROUGHING CONNECTED TO AN UPPER LOW OVER THE BAHAMAS IS PRESENT OVER THE FAR NW CARIBBEAN...BUT IS ACCOMPANIED BY DRY AIR. THE REMAINDER OF THE BASIN IS COVERED BY BROAD UPPER RIDGING CENTERED NEAR 13N79W. SCATTERED SHOWERS/THUNDERSTORMS ARE BEGINNING TO IMPACT THE WINDWARD ISLANDS FROM 11N-15N EAST OF 62W AHEAD OF TROPICAL STORM CHANTAL. WINDY CONDITIONS SHOULD BEGIN SOON ALONG WITH CONTINUED SHOWERS/THUNDERSTORMS. THE STORM IS EXPECTED TO REACH THE LESSER ANTILLES LATER THIS MORNING AND BE IN THE CENTRAL CARIBBEAN BY MIDDAY WEDNESDAY. INTERESTS IN THE EASTERN/CENTRAL CARIBBEAN SHOULD MONITOR THE PROGRESS OF CHANTAL. HISPANIOLA... SHOWER ACTIVITY HAS DIED DOWN OVER THE PAST FEW HOURS WITH ONLY AN AREA OF SCATTERED SHOWERS/THUNDERSTORMS SOUTH OF THE DOMINICAN REPUBLIC. A SLOT OF DRIER AIR IS EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY AHEAD OF MOISTURE WITH CHANTAL WHICH MAY PROVIDE FAIR CONDITIONS. CHANTAL IS EXPECTED TO BE NEAR HISPANIOLA BY MIDDAY WEDNESDAY. HEAVY RAINFALL IS POSSIBLE AND THE PROGRESS OF CHANTAL SHOULD BE WATCHED CLOSELY. TROPICAL STORM WATCHES AND WARNINGS ARE UP FOR MOST OF HISPANIOLA. ATLANTIC OCEAN... TROPICAL STORM CHANTAL IS IN THE TROPICAL ATLC. SEE SPECIAL FEATURES ABOVE. BROAD SURFACE RIDGING IS OVER THE WEST ATLC AROUND A 1026 MB HIGH NEAR 33N65W. THE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE TO THE NORTH CENTERED NEAR 37N62W. HOWEVER...AN UPPER LEVEL LOW TO THE SOUTH OVER THE BAHAMAS NEAR 25N77W IS ENHANCING ACTIVITY OVER THE BAHAMAS. IT ALSO SUPPORTS A SURFACE TROUGH...SPLIT PORTION OF A TROPICAL WAVE TO THE SOUTH...ALONG 29N77W TO 24N79W. STRONG SHOWERS/THUNDERSTORMS ARE FROM 22N-27N BETWEEN 74W-78W. MORE SCATTERED ACTIVITY IS FARTHER NORTH FROM 28N-31N BETWEEN 71W-76W. ACROSS THE CENTRAL ATLC...A SURFACE TROUGH ENTERS THE AREA ALONG 32N53W TO 30N60W. ISOLATED SHOWERS/THUNDERSTORMS ARE WITHIN 30 NM OF THE AXIS. A SECOND SURFACE TROUGH IS FARTHER EAST ALONG 31N40W TO 28N47W. POSSIBLE ISOLATED SHOWERS ARE ALONG THE AXIS. SEVERAL UPPER LEVEL ANTI- CYCLONE CENTERS ARE THROUGHOUT THE CENTRAL AND EASTERN ATLC. ONE IS CENTERED NEAR 28N47W. A SECOND CENTER IS TO THE SOUTH NEAR 17N42W...EAST OF CHANTAL. THE THIRD CENTER IS NEAR 19N28W OVER THE EASTERN ATLC. AN UPPER TROUGH EXTENDS FROM 32N30W TO 23N44W. AT THE SURFACE...BROAD RIDGING IS PRESENT ANCHORED BY A 1023 MB AZORES HIGH. VERY DRY AIR IS THROUGHOUT THE EAST ATLC DUE TO THE PRESENCE OF A BROAD SAHARAN AIR LAYER...WHICH IS KEEPING CONDITIONS FAIR ACROSS MUCH OF THE AREA. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON