000 AXNT20 KNHC 171047 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1030 UTC... ...TROPICAL WAVES... TROPICAL WAVE EXTENDS ALONG 47/48W FROM 8N TO 19N. THE WAVE IS FAIRLY WELL ORGANIZED WITH CYCLONIC TURNING COVERING A BROAD AREA OF ABOUT FIVE DEGREES EITHER SIDE OF THE WAVE AXIS. A NARROW BAND...EXHIBITING CYCLONIC CURVATURE CONSISTING OF MODERATE CONVECTION IS DEVELOPING ON THE WEST SIDE OF THE WAVE AXIS. 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. 850 MB MODEL GUIDANCE SUGGEST A VORTICITY MAXIMUM NEAR 12N48W WHERE FIRST VISIBLE SATELLITE PICTURE OF THE DAY SHOWS A SMALL CLUSTER OF SHOWERS AND ISOLATED TSTMS. AN EARLIER ASCAT PASS 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 31N. THIS WAVE WILL REACH 55W TONIGHT AND THE EASTERN CARIBBEAN SUN NIGHT BRINGING AN INCREASE IN SHOWER AND TSTM ACTIVITY PARTICULARLY ACROSS 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 62W S OF 17N. 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 BETWEEN GUADELOUPE AND DOMINICA. THE WAVE WILL MOVE THROUGH THE REMAINDER OF THE EASTERN CARIBBEAN SEA THROUGH TONIGHT...THEN ACROSS THE CENTRAL CARIBBEAN SUN AND MON. TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 72W MOVING W AT ABOUT 10 KT. THE WAVE EXTENDS FROM HISPANIOLA TO NEAR LAKE MARACAIBO IN WESTERN VENEZUELA. CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ARE OVER MUCH OF THE EASTERN CARIBBEAN WITH THE STRONGEST ONE BETWEEN BUOY 42959 AND THE ABC ISLANDS. THE WAVE IS ALSO ENHANCING CONVECTION JUST S OF HAITI AND NEAR THE COAST OF COLOMBIA. THIS SYSTEM WILL MOVE INTO THE W CARIBBEAN THIS EARLY TONIGHT. ...ITCZ... THE ITCZ AXIS IS ALONG 10N15W 7N30W 10N44W 9N50W 12N58W. SCATTERED MODERATE CONVECTION IS FROM 5N-8N BETWEEN 15W AND 27W. SIMILAR CONVECTION IS NEAR 7N41W. ...DISCUSSION... GULF OF MEXICO... A SURFACE TROUGH CONTINUES TO MOVE WWD ACROSS THE GULF WITH AXIS ALONG 92W S OF 27N TO THE BAY OF CAMPECHE. DEEP LAYER MOISTURE IS NOTED BETWEEN THE TROUGH AXIS AND AN UPPER-LEVEL LOW SPINNING NEAR THE FLORIDA KEYS. SCATTERED SHOWERS AND ISOLATED TSTMS ARE NEAR THE TROUGH AXIS WHICH IS FORECAST TO APPROACH THE TEXAS COAST TONIGHT WHILE WEAKENING. 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 WESTERN CARIBBEAN SEA...BUT NONE OF THIS ACTIVITY IS CONCENTRATED NEAR THE CENTER OF THE LOW. A SURFACE TROUGH IS ANALYZED IN THIS AREA EXTENDING FROM 21N85W TO A 1011 MB LOW PRES LOCATED NEAR 13N83W. 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. AN ASCAT PASS FROM 0308 UTC SHOWED THE WIND SHIFT ASSOCIATED WITH THE TROUGH AND WEAK CYCLONIC CIRCULATION RELATED TO THE LOW CENTER. E TO SE WINDS OF 15-20 KT CAN BE FOUND E OF THE TROUGH AXIS. CONVECTION HAS FLARED UP EARLY THIS MORNING OVER THE WESTERN CARIBBEAN NEAR AND EAST OF THE THE TROUGH AXIS WITH A CLUSTER OF MODERATE TO STRONG CONVECTION BETWEEN CUBA AND JAMAICA. ANOTHER SURFACE TROUGH PERSISTS OVER THE NE CARIBBEAN STRETCHING FROM E PUERTO RICO NE TO NEAR 22N65W. THIS TROUGH IS THE SURFACE REFLECTION OF AN UPPER-LEVEL LOW CENTERED NEAR 22N64W. THE SAN JUAN DOPPLER RADAR REVEALS SCATTERED TO NUMEROUS SHOWERS WITH EMBEDDED TSTMS...MORE CONCENTRATED SE OF PUERTO RICO. THE UPPER LOW IS FORECAST TO BRING ACTIVE WEATHER TO PUERTO RICO AND THE VIRGIN ISLANDS TODAY. 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 COVERS THE TROPICAL ATLC. AT THE SURFACE...RIDGING DOMINATES THE BASIN ANCHORED BY A SERIES OF HIGH CENTERS LOCATED 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