000 AXNT20 KNHC 181141 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT WED SEP 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURES... THE CENTER OF TROPICAL STORM HUMBERTO AT 18/0900 UTC IS NEAR 31.4N 43.7W OR ABOUT 913 NM W-SW OF THE AZORES. ITS PRESENT MOVEMENT IS N-NW AT 7 KNOTS AND THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 35 KNOTS WITH GUSTS TO 45 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. PRESENTLY...MOST OF THE CONVECTION LIES E AND SE OF THE LOW CENTER AS SCATTERED MODERATE CONVECTION FROM 28N-33N BETWEEN 38W-42W. A 1005 MB LOW PRESSURE CENTER IS IN THE YUCATAN PENINSULA NEAR 19N89W. NORTHWESTERLY WIND SHEAR IS KEEPING A CLUSTER OF MODERATE/ISOLATED STRONG CONVECTION NE OF THE LOW CENTER FROM 19N-22N BETWEEN 86W-88W. NUMEROUS MODERATE TO ISOLATED STRONG CONVECTION IS OVER THE NW CARIBBEAN SEA FROM 16N-22N BETWEEN 81W- 85W. ENVIRONMENTAL CONDITIONS ARE LIKELY TO BE CONDUCIVE FOR A TROPICAL DEPRESSION TO FORM OVER THE BAY OF CAMPECHE DURING THE NEXT COUPLE OF DAYS AFTER THE LOW MOVES INTO THE REGION ON WEDNESDAY. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE THE SYSTEM LATER TODAY...IF NECESSARY. REGARDLESS OF TROPICAL CYCLONE FORMATION...THIS DISTURBANCE WILL LIKELY SPREAD HEAVY RAINS OVER EASTERN MEXICO. THESE RAINS COULD CAUSE LIFE-THREATENING FLOODS AND MUDSLIDES OVER AREAS ALREADY IMPACTED BY THE TORRENTIAL RAINS ASSOCIATED WITH INGRID AND MANUEL. ...TROPICAL WAVES... THE AXIS OF A TROPICAL WAVE IS WEST OF THE CAPE VERDE ISLANDS ALONG 19N24W TO 12N28W AND IS MOVING W NEAR 5 KNOTS. METEOSAT SATELLITE IMAGERY CONTINUE TO SHOW INTRUSION OF SAHARAN DRY AIR INTO THE WAVE ENVIRONMENT WHICH IS LIMITING CONVECTIVE ACTIVITY. SCATTERED SHOWERS ARE NE OF THE WAVE AXIS FROM 19N- 21N...COINCIDING WITH A SMALL REGION OF HIGH MOISTURE DEPICTED IN TOTAL PRECIPITABLE WATER IMAGERY. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH PASSES THROUGH COASTAL WEST AFRICA NEAR 16N16W TO 13N25W TO 09N32W. THE ITCZ CONTINUES FROM 09N32W TO 10N42W TO 11N51W. SCATTERED MODERATE CONVECTION IS FROM 05N-12N BETWEEN 18W-32W...AS WELL AS FROM 07N-09N BETWEEN 40W-43W. ...DISCUSSION... THE GULF OF MEXICO... SCATTERED SHOWERS...REMNANTS OF INGRID ARE OVER THE W-NW GULF N OF 22N WEST OF 90W. AN UPPER-LEVEL SHORTWAVE TROUGH OVER THE NE GULF CONTINUE TO SUPPORT A STATIONARY FRONT THAT EXTENDS ACROSS NORTH-CENTRAL FLORIDA TO 29N83W TO 30N85W TO SOUTHERN ALABAMA NEAR 30N87W. RAINSHOWERS ASSOCIATED WITH THIS FRONTAL BOUNDARY ARE N OF 28N BETWEEN 85W-88W. A BROAD UPPER-LEVEL RIDGE COVERING THE WESTERN CARIBBEAN BASIN EXTENDS TO THE FLORIDA STRAITS. JUST WEST OF THIS RIDGE...AN INVERTED TROUGH IS GENERATING DIFFLUENT FLOW ALOFT TO SUPPORT THE CONVECTION ASSOCIATED WITH THE DISTURBANCE OVER THE YUCATAN PENINSULA. SEE THE SPECIAL FEATURES SECTION. FAIR WEATHER IS ELSEWHERE IN THE BASIN BEING SUPPORTED BY A TONGUE OF VERY DRY AIR PRESENT IN WATER VAPOR IMAGERY. THE DISTURBANCE IS EXPECTED TO ENTER THE BAY OF CAMPECHE LATER THIS MORNING. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE IN THE NEXT 48 HOURS. THE CARIBBEAN SEA... A BROAD UPPER-LEVEL RIDGE COVERS THE WESTERN CARIBBEAN BASIN WHICH EXTENDS TO THE FLORIDA STRAITS. JUST WEST OF THIS RIDGE...AN INVERTED TROUGH IS ACROSS THE NORTHERN CENTRAL AMERICA AND THE YUCATAN PENINSULA THUS GENERATING DIFFLUENT FLOW ALOFT TO SUPPORT THE CONVECTION IN THE NW BASIN ASSOCIATED WITH THE DISTURBANCE IN THE YUCATAN PENINSULA. THE MONSOON TROUGH AXIS EXTENDS FROM NORTHERN COLOMBIA TO NW HONDURAS THUS SUPPORTING NUMEROUS MODERATE/ISOLATED STRONG CONVECTION AND TSTMS IN THE SOUTHERN CARIBBEAN S OF 11N BETWEEN 75W-81W. AN UPPER-LEVEL RIDGE IS CENTERED E OF THE LESSER ANTILLES BUT EXTENDS TO THE EASTERN CARIBBEAN E OF 65W. DIFFLUENT FLOW ALOFT GENERATED BY NEARLY EASTERLY UPPER-LEVEL FLOW OVER NORTHERN SOUTH AMERICA IS SUPPORTING ISOLATED SHOWERS S OF 17N E OF 66W...INCLUDING THE LESSER ANTILLES. THE DISTURBANCE CURRENTLY MOVING ACROSS THE YUCATAN PENINSULA IS EXPECTED TO MOVE WEST- NORTHWESTWARD AND EMERGE OVER THE BAY OF CAMPECHE LATER TODAY...WHERE ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE CONDUCIVE FOR THE FORMATION OF A TROPICAL DEPRESSION OVER THE NEXT DAY OR TWO. CONVECTIVE ACTIVITY OVER THE NW BASIN IS EXPECTED TO CONTINUE THROUGH LATE WED NIGHT. HISPANIOLA... CURRENTLY DRY STABLE AIR IS ACROSS MOST OF THE ISLAND THIS MORNING WHICH IS FAVORING FAIR WEATHER. AN UPPER-LEVEL TROUGH MOVES ACROSS THE DOMINICAN REPUBLIC AND PUERTO RICO WHILE THE RIDGE OVER THE WESTERN CARIBBEAN EXTENDS TO HAITI. THIS IS CAUSING DIFFLUENCE ALOFT TO SUPPORT ISOLATED SHOWERS AND TSTMS ACROSS THE ISLAND. EXPECT RAINSHOWERS TO DEVELOP DURING THE AFTERNOON AND EVENING HOURS TODAY THOROUGH THURSDAY. THE ATLANTIC OCEAN... THE MAIN FEATURE IN THE ATLC IS TROPICAL STORM HUMBERTO WHICH INFORMATION IS PROVIDED IN THE SPECIAL FEATURES SECTION. AN UPPER-LEVEL TROUGH IN THE W ATLC SUPPORTS A FRONTAL SYSTEM THAT ENTERS THE DISCUSSION AREA AS A STATIONARY FRONT FROM 30N67W TO 29N75W TO THE EASTERN COAST OF FLORIDA NEAR 29N81W. DIFFLUENT FLOW ALOFT FROM THE UPPER-LEVEL TROUGH AND THE RIDGE COVERING THE BAHAMAS AND THE WESTERN CARIBBEAN SUPPORTS SCATTERED SHOWERS N OF 23N W OF 72W. A SURFACE TROUGH IS FROM 28N66W TO 25N70W GENERATING SCATTERED SHOWERS AND TSTMS FROM 25N-27N BETWEEN 68W- 70W. A SURFACE TROUGH IS N OF THE ITCZ ALONG 19N44W TO 12N47W GENERATING SCATTERED SHOWERS FROM 13N-17N BETWEEN 42W-47W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ NR/PAW