000 AXNT20 KNHC 171039 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT FRI JUL 17 2015 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 1030 UTC. ...TROPICAL WAVES... A TROPICAL WAVE WAS RE-INTRODUCED TO THE ANALYSIS THIS MORNING. THIS WAVE HAS AN AXIS THAT EXTENDS FROM 17N37W TO A 1011 MB LOW CENTERED NEAR 10N37W. THESE FEATURES ARE INTERACTING WITH EACH OTHER AND CURRENT GUIDANCE SHOW THE LOW DISSIPATING WITHIN THE NEXT 48 HOURS LEAVING THE WAVE MOVING BY ITSELF ACROSS THE CENTRAL ATLANTIC AND E CARIBBEAN. TPW IMAGERY DEPICTS A HIGH MOISTURE CONTENT MAINLY E OF THE WAVE AXIS BETWEEN 03N-16N. SCATTERED MODERATE CONVECTION IS OBSERVED FROM 03N-15N BETWEEN 29W-39W. A TROPICAL WAVE IS OVER THE W CARIBBEAN WITH AXIS APPROXIMATELY ALONG 77W AND FROM 10N TO 19N...MOVING W AT 20-25 KT DURING THE LAST 24 HOURS. SSMI TPW IMAGERY DEPICT A MODERATE MOIST AIRMASS ASSOCIATED WITH THIS WAVE PREVAILING ACROSS THE NORTHERN PORTION OF THE WAVE AND EXTENDING ACROSS THE E CARIBBEAN MAINLY N OF 14N. SAHARAN DUST AND STRONG DEEP-LAYER WIND SHEAR ARE ALSO PREVAILING ACROSS THIS AREA THUS NO SIGNIFICANT CONVECTION IS OBSERVED AT THIS TIME. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 19N16W TO A 1011 MB SURFACE LOW CENTERED NEAR 10N37W TO 08N47W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 08N47W TO 06N57W. SCATTERED MODERATE CONVECTION IS OBSERVED SURROUNDING THE LOW FROM 03N-15N BETWEEN 29W-39W. ...DISCUSSION... GULF OF MEXICO... A BROAD SURFACE RIDGE COVERING A GREAT PORTION OF THE ATLANTIC BASIN EXTENDS W REACHING THE GULF WATERS AND ANCHORED BY A 1018 MB HIGH NEAR 25N86W. ALOFT...AN UPPER-LEVEL LOW IS OBSERVED CENTERED OVER SOUTHERN MEXICO AND EXTENDING EASTWARD ACROSS THE BAY OF CAMPECHE BRINGING MOISTURE FROM THE EPAC INTO THE W GULF. WITH THIS...ISOLATED CONVECTION IS DEVELOPING ACROSS THE SW GULF MAINLY W OF 94W. A BROAD UPPER-LEVEL HIGH IS CENTERED NEAR 29N90W AND EXTENDING ACROSS THE NORTHERN HALF OF THE GULF. THIS FEATURE COMBINED WITH THE UPPER-LEVEL LOW OVER THE W CARIBBEAN GENERATES A DIFFLUENT FLOW ACROSS THE E PORTION OF THE BASIN SUPPORTING ISOLATED CONVECTION E OF 86W. SCATTEROMETER DATA DEPICTS A LIGHT ANTICYCLONIC FLOW ACROSS MOST OF THE BASIN EXCEPT N OF THE YUCATAN PENINSULA S OF 24N BETWEEN 88W-91W WHERE LIGHT TO GENTLE FLOW IS OBSERVED. EXPECT FOR THE RIDGE TO REMAIN NEARLY STATIONARY THROUGH THE NEXT 24 HOURS ACROSS THE BASIN AND WITH A SIMILAR WEATHER PATTERN PREVAILING. CARIBBEAN SEA... A TROPICAL WAVE IS MOVING ACROSS THE W CARIBBEAN. PLEASE REFER TO THE SECTION ABOVE FOR MORE DETAILS. AN AREA OF MODERATE MOISTURE PREVAILS ACROSS THE NE AND CENTRAL CARIBBEAN N OF 14N AND E OF 73W. THIS MOISTURE ALONG WITH AN UPPER-LEVEL LOW CENTERED NE OF THE LEEWARD ISLANDS IS SUPPORTING ISOLATED MODERATE CONVECTION ACROSS THE MONA PASSAGE AND HISPANIOLA AS WELL AS THE ADJACENT WATERS N OF 17N BETWEEN 68W-72W. ANOTHER AREA OF MODERATE MOISTURE PREVAILS ACROSS THE W CARIBBEAN W OF 78W AND WITH SUPPORT OF AN UPPER-LEVEL LOW CENTERED OVER W CUBA...ISOLATED SHOWERS PREVAIL N OF 15N AND W OF 75W. OVER THE SW CARIBBEAN...THE PROXIMITY OF THE MONSOON TROUGH S OF PANAMA AND A SURFACE LOW OVER NE COLOMBIA ARE PRODUCING SCATTERED MODERATE CONVECTION THAT IS MOVING OVER THE SOUTHERN CARIBBEAN WATERS MAINLY S OF 10N. A STRONG DEEP LAYER WIND SHEAR AND DRY AIR CONTINUES TO INHIBIT CONVECTION ELSEWHERE. A GENERALLY TIGHT PRESSURE GRADIENT BETWEEN THE RIDGE OVER THE ATLANTIC EXTENDING ACROSS THE NORTHERN BASIN AND LOWER PRESSURES OVER COLOMBIA AND SOUTH AMERICA SUPPORTS GENTLE TO MODERATE TRADES ACROSS MOST OF THE BASIN EXCEPT N OF 18N AND W OF 73W WHERE A LIGHT EASTERLY FLOW PREVAILS. OVER THE NEXT 24 HOURS...EXPECT FOR THE TROPICAL WAVE TO CONTINUE MOVING W ACROSS THE W CARIBBEAN WITH AN INCREASE IN MOISTURE. A SIMILAR WEATHER PATTERN WILL PREVAIL ACROSS THE BASIN. ...HISPANIOLA... THE MOISTURE ASSOCIATED WITH THE PASSAGE OF A TROPICAL WAVE WITH AXIS S OF THE ISLAND NEAR 74W COMBINED THE PROXIMITY OF AN UPPER LEVEL LOW CURRENTLY OVER W CUBA SUPPORTS ISOLATED MODERATE CONVECTION ACROSS THE ISLAND. SIMILAR ACTIVITY IS POSSIBLE OVER THE NEXT 24 HOURS. ATLANTIC OCEAN... AN UPPER-LEVEL TROUGH PREVAILS OVER THE W ATLANTIC WITH BASE N OF OUR AREA AND SUPPORTING A STATIONARY FRONT THAT IS CURRENTLY GENERATING SCATTERED MODERATE CONVECTION N OF 29N AND W OF 68W. AN UPPER-LEVEL LOW CENTERED OVER W CUBA EXTENDS ACROSS THE BAHAMAS SUPPORTING ISOLATED CONVECTION S OF 25N AND W OF 76W. ANOTHER UPPER LEVEL LOW IS CENTERED NEAR 20N61W. ISOLATED CONVECTION IS DEVELOPING IN THE NORTHERN PERIPHERY OF THIS LOW FROM 22N-27N BETWEEN 48W-60W. THE CENTRAL AND E ATLANTIC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1023 MB HIGH CENTERED NEAR 28N63W AND A 1021 MB HIGH CENTERED NEAR 33N28W. A WEAKNESS BETWEEN THESE TWO HIGHS IS ANALYZED AS A SURFACE TROUGH FROM 27N51W TO 31N44W. OVER THE NEXT 24 HOURS...EXPECT FOR THE SURFACE RIDGE TO PREVAIL ACROSS THE BASIN WITH FAIR WEATHER. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ ERA