000 AXNT20 KNHC 191158 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT THU SEP 19 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... THE CENTER OF TROPICAL DEPRESSION HUMBERTO AT 19/0900 UTC IS NEAR 33.0N 44.3W OR ABOUT 896 NM W-SW OF THE AZORES. PRESENT MOVEMENT IS N AT 7 KNOTS AND THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 30 KNOTS WITH GUSTS TO 40 KNOTS. PLEASE READ THE PUBLIC ADVISORIES ABOUT HUMBERTO THAT ARE ISSUED UNDER WMO HEADER WTNT34 KNHC AND UNDER AWIPS HEADER MIATCPAT4... AND THE FORECAST/ADVISORIES THAT ARE ISSUED UNDER WMO HEADER WTNT24 KNHC AND UNDER AWIPS HEADER MIATCMAT4. SCATTERED MODERATE CONVECTION IS FROM 29N-32N BETWEEN 40W-44W. A 1004 MB LOW PRESSURE CENTER IS OVER THE BAY OF CAMPECHE NEAR 20N93W. THE CONVECTION PREVIOUSLY INLAND S-SE MEXICO AND GUATEMALA MERGED TO FORM A CLUSTER OF MODERATE/ISOLATED STRONG CONVECTION OVER THE BAY OF CAMPECHE S OF 20N BETWEEN 91W-94W. CONDITIONS STILL APPEAR CONDUCIVE FOR THE FORMATION OF A TROPICAL DEPRESSION DURING THE NEXT DAY OR TWO...AND AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE THE LOW THIS AFTERNOON...IF NECESSARY. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS WHILE IT MOVES TO THE WEST-NORTHWEST TO NORTHWESTWARD. THIS DISTURBANCE WILL LIKELY SPREAD HEAVY RAIN OVER PORTIONS OF EASTERN AND SOUTHERN MEXICO AND COULD CAUSE LIFE-THREATENING FLOODS AND MUDSLIDES OVER AREAS ALREADY IMPACTED BY TORRENTIAL RAIN DURING THE PAST SEVERAL DAYS. ...TROPICAL WAVES... THE AXIS OF A TROPICAL WAVE IS WEST OF THE CAPE VERDE ISLANDS ALONG 21N29W TO 10N30W AND IS MOVING W NEAR 10 KNOTS. METEOSAT SATELLITE IMAGERY CONTINUE TO SHOW DRY AIR INTRUSION TO THE NORTHERN SECTOR OF THE WAVE WHICH IS HINDERING CONVECTION. SCATTERED MODERATE CONVECTION DEVELOPED NE OF THE THE WAVE AXIS FROM 19N-22N BETWEEN 26W-29W COINCIDING WITH A SMALL REGION OF VERY MOIST AIR IN THE TOTAL PRECIPITABLE WATER IMAGERY. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH PASSES THROUGH COASTAL WEST AFRICA NEAR 12N16W TO 10N24W. THE ITCZ CONTINUES FROM 10N24W TO 09N42W TO 12N59W. SCATTERED MODERATE CONVECTION IS FROM 03N-11N BETWEEN 26W-41W AND FROM 07N-12N BETWEEN 47W-53W. ...DISCUSSION... THE GULF OF MEXICO... A VERY MOIST ENVIRONMENT AT THE LOWER AND MIDDLE LEVELS DOMINATE THE GULF WATERS AS DEPICTED IN IMAGERY OF TOTAL PRECIPITABLE WATER AND WATER VAPOR. HOWEVER...STRONG NORTHWESTERLY WIND SHEAR IS INHIBITING IN PART CONVECTIVE ACTIVITY ACROSS GREAT PORTIONS OF THE BASIN. A DISTURBANCE IS BEING ANALYZED IN THE SW GULF. SEE THE SPECIAL FEATURES SECTION. A WEAK UPPER-LEVEL TROUGH OVER THE EASTERN GULF SUPPORTS A DISSIPATING STATIONARY FRONT ACROSS NORTH-CENTRAL FLORIDA TO 28N82W TO 29N86W. ISOLATED SHOWERS ASSOCIATED WITH THIS FRONTAL BOUNDARY ARE N OF 28N E OF 87W. DIFFLUENT FLOW ALOFT FROM THE TROUGH OVER THE EASTERN GULF AND AN UPPER-LEVEL RIDGE COVERING THE WESTERN CARIBBEAN SEA CONTINUES TO SUPPORT SCATTERED SHOWERS IN THE FLORIDA STRAITS AND THE YUCATAN CHANNEL. THERE IS A HIGH CHANCE FOR THE DISTURBANCE TO BECOME A TROPICAL CYCLONE DURING THE NEXT 48. HEAVY RAIN OVER PORTIONS OF EASTERN AND SOUTHERN MEXICO IS EXPECTED. THE CARIBBEAN SEA... A VERY MOIST ENVIRONMENT AT THE LOWER AND MIDDLE LEVELS DOMINATE THE CARIBBEAN WATERS AS DEPICTED IN IMAGERY OF TOTAL PRECIPITABLE WATER AND WATER VAPOR. UPPER-LEVEL DIVERGENCE FROM A BROAD RIDGE COVERING THE BAHAMAS AND THE WESTERN-CENTRAL CARIBBEAN SEA SUPPORTS SCATTERED SHOWERS AND TSTMS S OF 19N W OF 83W. AN UPPER-LEVEL LOW IS OVER THE CENTRAL-EASTERN BASIN BETWEEN 65W-71W THUS GENERATING DIFFLUENCE TO SUPPORT SCATTERED MODERATE/ISOLATED STRONG CONVECTION AND TSTMS S OF 14N BETWEEN 72W-78W. THIS CONVECTION IS ALSO ASSOCIATED WITH THE MONSOON TROUGH WHICH AXIS ENDS UP IN NORTHERN COLOMBIA. SIMILAR CONVECTION ALSO ASSOCIATED WITH THE MONSOON TROUGH IS OFFSHORE NICARAGUA AND COSTA RICA FROM 09N-13N W OF 81W. SCATTERED MODERATE CONVECTION AND TSTMS ARE JUST WEST OF THE LEEWARD ISLANDS FROM 14N-18N BETWEEN 61W-65W. A SURFACE TROUGH IS EXPECTED TO ENTER THE EASTERN CARIBBEAN SEA SATURDAY AFTERNOON WHILE AN AREA OF LOW PRESSURE IS EXPECTED TO DEVELOP N OF THE AREA JUST EAST OF THE BAHAMAS. THESE FEATURES MAY GENERATE SHOWERS POSSIBLY AFFECTING THE GREATER AND LESSER ANTILLES. HISPANIOLA... UPPER-LEVEL DIFFLUENCE FROM AN UPPER-LEVEL RIDGE COVERING THE BAHAMAS AS WELL AS THE WESTERN-CENTRAL CARIBBEAN AND A LOW OVER THE CENTRAL-EASTERN BASIN IS SUPPORTING ISOLATED SHOWERS AND TSTMS ACROSS THE ISLAND AND ADJACENT WATERS. BESIDES THE TYPICAL AFTERNOON/EARLY EVENING SHOWERS ACTIVITY DUE TO SURFACE HEATING...EXPECT LITTLE CHANGES IN THE NEXT 48 HOURS. THE ATLANTIC OCEAN... THE MAIN FEATURE IN THE ATLC IS TROPICAL DEPRESSION HUMBERTO WHICH INFORMATION IS PROVIDED IN THE SPECIAL FEATURES SECTION. A WEAK UPPER-LEVEL TROUGH IN THE W ATLC SUPPORTS A FRONTAL SYSTEM THAT ENTERS THE DISCUSSION AREA AS A STATIONARY FRONT FROM 30N58W TO 28N75W WHERE IT TRANSITIONS TO A DISSIPATING STATIONARY FRONT TO THE EASTERN COAST OF FLORIDA NEAR 28N80W. A PRE-FRONTAL SURFACE TROUGH EXTENDS FROM 28N68W TO 25N76W. SCATTERED MODERATE CONVECTION AND ISOLATED TSTMS ASSOCIATED WITH THE FRONT AND THE TROUGH ARE FROM 24N-30N BETWEEN 57W-75W. DIFFLUENT FLOW ALOFT FROM THE UPPER-LEVEL TROUGH AND A RIDGE COVERING THE BAHAMAS AND THE WESTERN-CENTRAL CARIBBEAN SUPPORTS SCATTERED SHOWERS IN THE BAHAMAS AND N OF CUBA BETWEEN 70W-82W. FURTHER EAST...A 1017 MB HIGH PRESSURE CENTER IS NEAR 24N53W WHICH IS EXPECTED TO DISSIPATE WITHIN THE NEXT 24 HOURS. A SURFACE TROUGH WITH NO CONVECTION ASSOCIATED WITH IT EXTENDS FROM 18N49W TO 12N53W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ NR/PAW