000 AXNT20 KNHC 170550 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SAT JUL 17 2010 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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC... ...TROPICAL WAVES... A WELL DEFINED TROPICAL WAVE EXTENDS FROM 19N43W TO 8N45W WITH SOME CYCLONIC TURNING ALONG THE WAVE AXIS NEAR 16N. THE WAVE IS MOVING W NEAR 20 KT AND REMAINS EMBEDDED WITHIN AN AREA OF DEEP LAYER MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER ANIMATION. AN ASCAT PASS FROM 2348 UTC INDICATED NE WINDS OF 20 KT NEAR THE NORTHERN END OF THE WAVE AXIS DUE TO THE PRES GRADIENT BETWEEN THIS SYSTEM AND THE ATLC RIDGE EXTENDING ALONG 32N. SAHARAN AIR LAYER IN THE VICINITY OF THE WAVE IS SUPPRESSING CONVECTION FROM DEVELOPING...LEAVING ONLY SCATTERED SHOWERS AND ISOLATED TSTMS NEAR 12N46W. THIS WAVE WILL REACH 55W THIS EVENING AND THE EASTERN CARIBBEAN SUN NIGHT BRINGING AN INCREASE IN SHOWER AND TSTMS ACTIVITY PARTICULARLY TO THE LEEWARD ISLANDS AND THEN OVER PUERTO RICO AND THE US/UK VIRGIN ISLANDS BY MON. TROPICAL WAVE IS MOVING ACROSS THE LESSER ANTILLES WITH AXIS ALONG 61W FROM 8N TO 16N. THIS FEATURE IS MOVING W ABOUT 15 KT. A DIFFLUENT PATTERN ALOFT BETWEEN AN UPPER-LEVEL LOW APPROACHING PUERTO RICO AND A RIDGE OVER THE EASTERN CARIBBEAN IS HELPING TO INDUCE CONVECTION NEAR THE WAVE AXIS. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS SEEN FROM 14N TO 18N BETWEEN 60W AND 63W. TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 71W S OF 17N MOVING W AT ABOUT 10 KT. SCATTERED MODERATE TO STRONG CONVECTION CAN BE FOUND WITHIN AROUND 200 NM EITHER SIDE OF THE WAVE AXIS S OF 13N TO THE COAST OF SOUTH AMERICA...INCLUDING INLAND PORTIONS OF WESTERN VENEZUELA AND EASTERN COLOMBIA. THE WAVE IS ALSO ENHANCING CONVECTION JUST S OF HISPANIOLA. THIS WAVE WILL MOVE INTO THE W CARIBBEAN TODAY. ...ITCZ... THE ITCZ AXIS IS ALONG 10N15W 7N30W 10N44W 9N50W 12N58W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF THE AXIS E OF 33W TO THE WEST COAST OF AFRICA. SIMILAR CONVECTION IS FROM 5N-8N BETWEEN 38W AND 45W. ...DISCUSSION... GULF OF MEXICO... A SURFACE TROUGH CONTINUES TO MOVE WWD ACROSS THE CENTRAL GULF WITH AXIS ALONG 91W...FROM THE COAST OF LOUISIANA TO THE YUCATAN PENINSULA NEAR 19N90W. THERE ARE NO SIGNS OF ORGANIZATION AT THIS TIME...AND DEVELOPMENT...IF ANY...WILL BE SLOW TO OCCUR. ABUNDANT MID/UPPER LEVEL MOISTURE IS NOTED ON WATER VAPOR IMAGERY BETWEEN THE TROUGH AXIS AND AN UPPER-LEVEL LOW SPINNING NEAR THE FLORIDA KEYS. SCATTERED SHOWERS AND TSTMS ARE OVER THE EASTERN GULF MAINLY ASSOCIATED WITH THE UPPER LOW. SCATTERED SHOWERS ARE NEAR THE TROUGH AXIS WHICH IS FORECAST TO MOVE ACROSS THE WESTERN GULF THROUGH TONIGHT. A RIDGE FROM THE ATLC EXTENDS ACROSS THE FLORIDA PENINSULA INTO THE EASTERN GULF. THE RIDGE ALSO DOMINATES THE SE CONUS. A DRYER AIR MASS IS NOTED WEST OF THE SURFACE TROUGH. CARIBBEAN SEA... A BROAD AREA OF LOW PRESSURE LOCATED JUST EAST OF NICARAGUA CONTINUES TO PRODUCE DISORGANIZED SHOWERS AND THUNDERSTORMS OVER A LARGE PORTION OF THE SOUTHWESTERN CARIBBEAN SEA. A SURFACE TROUGH IS ANALYZED IN THIS AREA EXTENDING FROM 20N85W TO 12N82W. SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED DUE TO PROXIMITY TO LAND. HOWEVER...HEAVY RAIN WILL SPREAD OVER PORTIONS OF CENTRAL AMERICA DURING THE NEXT COUPLE OF DAYS AS THIS SYSTEM MOVES SLOWLY WESTWARD. ANOTHER SURFACE TROUGH PERSISTS OVER THE NE CARIBBEAN STRETCHING FROM PUERTO RICO NE TO 22N62W. THIS TROUGH IS THE SURFACE REFLECTION OF AN UPPER-LEVEL LOW CENTERED NEAR 22N64W. SCATTERED SHOWERS WITH EMBEDDED TSTMS ARE NEAR THE TROUGH AXIS AFFECTING PUERTO RICO AND COASTAL WATERS...PARTICULARLY ACROSS THE ATLC SIDE. A RAINFALL RECORD WAS SET TODAY AT THE SAN JUAN INTERNATIONAL AIRPORT WITH 1.73 INCHES OF RAIN. THIS BROKE THE OLD RECORD OF 0.98 INCHES SET BACK IN 1957. THE UPPER LOW IS FORECAST TO BRING ACTIVE WEATHER TO PUERTO RICO AND THE VIRGIN ISLANDS THIS SATURDAY. ATLANTIC OCEAN... ALOFT...AN UPPER-LEVEL LOW IS SPINNING NEAR THE FLORIDA KEYS WITH THE CYCLONIC FLOW COVERING FLORIDA...CUBA AND THE BAHAMAS MAINLY W OF 76W. AS PREVIOUSLY MENTIONED...ANOTHER UPPER LEVEL LOW IS NEAR 22N64W HELPING TO INDUCE CONVECTION NEAR PUERTO RICO. IN BETWEEN...THERE IS AN UPPER-LEVEL RIDGE EXTENDING S TO NEAR THE SE BAHAMAS. A RIDGE ALSO THE TROPICAL ATLC. AT THE SURFACE...RIDGING DOMINATES THE BASIN ANCHORED BY A SERIES OF HIGHS CENTERED N OF THE DISCUSSION AREA. THE STRONGEST ONE...ANALYZED 1028 MB...IS NEAR THE AZORES. PRES GRADIENT BETWEEN THE AZORES HIGH AND LOWER PRES OVER AFRICA IS PRODUCING AN AREA OF NLY WINDS IN THE 20 TO 25 KT RANGE BETWEEN THE CANARY AND THE CAPE VERDE ISLANDS MAINLY E OF 20W. DRY SAHARAN AIR LAYER ACCOMPANIED BY DUST COVERS MUCH OF THE TROPICAL ATLC SUPPRESSING CONVECTION IN THIS REGION. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GR