000 AXNT20 KNHC 020002 AAA TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE AUG 01 2006 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN SECTIONS OF SOUTH AMERICA...AND THE 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...SPECIAL FEATURE... TROPICAL STORM CHRIS HAS STRENGTHENED THIS AFTERNOON AS IT NEARS THE NORTHERNMOST LEEWARD ISLANDS. THE CENTER OF T.S. CHRIS IS LOCATED NEAR 18.3 NORTH 61.6 WEST OR ABOUT 45 NM...NORTHEAST OF ANTIGUA AT 02/0000 UTC. CHRIS IS MOVING TOWARD THE WEST-NORTHWEST NEAR 11 KT. ON THE FORECAST TRACK...CHRIS IS EXPECTED TO MOVE NEAR OR OVER THE NORTHERNMOST LEEWARD ISLANDS TONIGHT AND EARLY WED. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB. THE MAXIMUM SUSTAINED WINDS HAS INCREASED TO 50 KT WITH GUSTS TO 60 KT. CHRIS IS EXPECTED TO PRODUCE TOTAL RAINFALL AMOUNTS OF 3 TO 5 INCHES OVER THE NORTHERN LEEWARD ISLANDS...THE U.S. VIRGIN ISLANDS...AND EASTERN PORTIONS OF PUERTO RICO...WITH POSSIBLE ISOLATED MAXIMUM AMOUNTS OF 8 INCHES THROUGH WEDNESDAY. PLEASE REFER TO THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/ WTNT23 KNHC AND THE PUBLIC ADVISORY MIATCPAT3/WTNT33 KNHC FOR MORE DETAILS. A LONG ANIMATION LOOP OF INFRARED SATELLITE IMAGERY THROUGHOUT THE DAY SHOWS THE SYSTEM WITH TWO BROKEN BANDS OF CONVECTION. SINCE 18Z...THESE BANDS HAVE CONSOLIDATED LEAVING AN AREA OF SCATTERED MODERATE CONVECTION FROM 16N TO 18.6N BETWEEN 60W AND 62.5W. SOME NORTH/NORTHWESTERLY SHEAR IS STILL IMPACTING CHRIS... IN ASSOCIATION WITH AN UPPER LEVEL LOW TO ITS NNE...SHEARING MUCH OF THE CONVECTION TO THE SOUTHERN SEMI-CRICLE. HOWEVER...THE SHEAR DOES APPEAR TO BE DECREASING OVER THE SYSTEM AS OUTFLOW HAS IMPROVED ESPECIALLY IN THE EASTERN QUADRANT. CHRIS COULD MOVE INTO A LOW SHEAR MORE FAVORABLE ENVIRONMENT FOR STRENGTHENING OVER THE NEXT FEW DAYS. ...TROPICAL WAVES... A TROPICAL WAVE IN THE EASTERN ATLC HAS BEEN REPOSITIONED SLIGHTLY TO THE WEST ALONG 33W SOUTH OF 17N MOVING WEST 15-20 KT. THIS WAVE HAS VERY BROAD ELONGATED CYCLONIC TURNING ASSOCIATED WITH IT COVERING A REGION OVER 10 DEGREES OF LONGITUDE. THIS NEW POSITION PLACES THE WAVE AXIS NEAR OR SLIGHTLY EAST OF THE CENTER OF THIS BROAD CIRCULATION FOLLOWING THE INVERTED V-SHAPE EVIDENT ON SATELLITE IMAGERY. IN ADDITION....AN EXCELLENT QUIKSCAT PASS NEAR 21Z YESTERDAY SHOWED THE WAVE NEAR 27W/28W. THIS CURRENT POSITION IS IN A REASONABLE LOCATION BASED UPON THE GIVEN LOW-MID LEVEL STEERING FLOW. SCATTERED SHOWERS AND TSTMS EXIST FROM 12N-15N BETWEEN 27W-37W. MORE SHOWER ACTIVITY ENHANCED BY THE WAVE IS EMBEDDED IN THE ITCZ AND IS DISCUSSED IN THAT SECTION. THE LOW AMPLITUDE TROPICAL WAVE THAT WAS PREVIOUSLY ALONG 69W/70W S OF 15N IN THE CARIBBEAN SEA HAS BEEN DROPPED FROM THE SURFACE ANALYSIS. THE ANALYZED POSITION AT 12Z THIS MORNING EXTENDING BACK FOR THE LAST DAY OR SO HAS BEEN THE SOUTHERN PORTION OF THE WAVE THAT SPLIT JUST EAST OF THE LESSER ANTILLES...WITH THE NORTHERN PORTION NOW T.S. CHRIS. SINCE THE DEVELOPMENT OF THE TC...THIS WAVE HAS BECOME VERY DIFFICULT TO TRACK AND IT IS ASSUMED THAT THE SOUTHERN PORTION OF THE WAVE HAS DISSIPATED. A TROPICAL WAVE IS INLAND OVER THE YUCATAN PENINSULA ALONG 90W S OF 20N MOVING W NEAR 15 KT. THIS WAVE WILL MOVE W THROUGH THE BAY OF CAMPECHE LATER TONIGHT. A VERY FAINT INVERTED V PATTERN IS NOTED WITH THIS WAVE. THIS WAVE...ALONG WITH UPPER DIFFLUENCE BETWEEN AND UPPER RIDGE OVER S MEXICO AND ANOTHER UPPER RIDGE OVER THE CAYMANS IS GENERATING CLUSTERS OF MODERATE CONVECTION OVER BELIZE...NRN GUATEMALA...AND THE YUCATAN PENINSULA FROM 17N-21N BETWEEN 88W-91W. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 9N11W 11N26W 5N44W TO INLAND OVER SOUTH AMERICA NEAR 6N56W. CLUSTERS OF MODERATE CONVECTION IS ALONG THE COAST OF AFRICA E OF 16W FROM 8N-17N LIKELY ASSOCIATED WITH A DEVELOPING TROPICAL WAVE. SCATTERED SHOWERS AND TSTMS ARE WITHIN 240 NM TO THE SOUTH OF THE AXIS BETWEEN 20W-37W. ...DISCUSSION... THE GULF OF MEXICO... SCATTERED SHOWERS AND TSTMS ARE IN THE W GULF W OF 93W FROM 22N-27N. THIS ACTIVITY IS GENERATED BY WEAK UPPER DIFFLUENCE BETWEEN AN UPPER LEVEL LOW OVER NRN MEXICO/SRN TEXAS NEAR 27N99W AND AN UPPER HIGH OVER S MEXICO NEAR 19N96W. MUCH OF THE CENTRAL AND EASTERN GULF HAS A FAIR AMOUNT OF DRY STABLE AIR ALOFT LIMITING ANY SHOWER ACTIVITY TO ISOLATED. CLUSTERS OF MODERATE CONVECTION IS OVER THE YUCATAN PENINSULA MOVING INTO THE BAY OF CAMPECHE ASSOCIATED WITH THE TROPICAL WAVE ALONG 90W. SEE THE TROPICAL WAVES SECTION FOR MORE DETAILS. SCATTERED SHOWERS AND TSTMS HAVE MOVED NWARD INLAND OVER THE SRN U.S. ASSOCIATED WITH AN UPPER LOW OVER MISSISSIPPI. THE SFC PATTERN IN THE GULF REMAINS FAIRLY BENIGN WITH WEAK RIDGING STRETCHING ACROSS THE AREA FROM A 1020 MB HIGH CENTERED OVER NRN FLORIDA ALONG WITH THE WESTERN PORTION OF AN ATLC SURFACE RIDGE. THIS WEAK PATTERN IS PRODUCING LIGHT 5 TO 15 KT E/SE WINDS OVER MUCH OF THE GULF....EXCEPT NEAR THE HIGH CENTER WHERE WINDS ARE EVEN LIGHTER AND MORE VARIABLE. SIMILAR CONDITIONS ARE EXPECTED THE NEXT COUPLE OF DAYS AS A FAIRLY WEAK SURFACE ANTICYCLONE PATTERN DOMINATES WITH THE GREATEST RAIN CHANCES IN THE SRN GULF. THE CARIBBEAN SEA... THE MAIN FEATURE IN THE REGION IS TROPICAL STORM CHRIS WHICH IS AFFECTING THE NRN LEEWARD ISLANDS. GUSTY WINDS AND SCATTERED MODERATE CONVECTION IS N OF 16N BETWEEN 58W-63W. FOR MORE DETAILS...REFER TO THE SPECIAL FEATURE SECTION ABOVE. BESIDES FOR T.S. CHRIS THERE ARE TWO OTHER AREAS OF UNSETTLED WEATHER IN THE CARIBBEAN. SCATTERED MODERATE CONVECTION LIES N OF 17N BETWEEN 74W-85W COVERING JAMAICA...THE CAYMAN ISLANDS AND CUBA...MAINLY ASSOCIATED WITH UPPER DIFFLUENT FLOW BETWEEN AN UPPER HIGH CENTERED NEAR THE CAYMAN ISLANDS AND A WELL-DEFINED UPPER LOW E OF THE BAHAMAS NEAR 26N72W. THE STRONGEST ACTIVITY IS OVER CUBA ENHANCED BY LOCAL EFFECTS. THE OTHER AREA OF SCATTERED MODERATE CONVECTION IS OVER THE YUCATAN PENINSULA AND BELIZE FROM 17N-21N BETWEEN 88W-91W ASSOCIATED WITH A TROPICAL WAVE AND UPPER DIFFLUENT FLOW BETWEEN AN UPPER HIGH OVER S MEXICO AND THE UPPER HIGH OVER THE CAYMAN ISLANDS. THE REMAINDER OF THE CARIBBEAN HAS A DRY/STABLE UPPER LEVEL ENVIRONMENT UNDER WEAK UPPER RIDGING WITH THE AXIS ALONG 19N/20N E OF 83W. AT THE SURFACE...10 TO 20 KT E TO SE TRADE WINDS ARE DOMINATING ON THE SW SIDE OF THE ATLANTIC HIGH. QUIKSCAT DATA FROM THIS MORNING SHOWED SLIGHTLY STRONGER 20 TO 25 KT E WINDS IN THE CENTRAL CARIBBEAN WATERS BETWEEN VENEZUELA/COLOMBIA AND HISPANIOLA. THE ATLANTIC OCEAN... AM AMPLIFIED UPPER LEVEL PATTERN EXISTS IN THE WRN ATLANTIC WITH A NW-SE TITLED UPPER HIGH OVER THE MID-ATLC U.S. AND AN UPPER LOW ABOUT 200 NM NE OF THE BAHAMAS. THIS UPPER LOW HAS A SFC REFLECTION ANALYZED AS A TROUGH FROM 23N73W TO 28N68W. HOWEVER...BASED UPON THE LATEST QUIKSCAT PASS THIS REFLECTION MAY BE OFF THE SFC. ONLY ISOLATED SHOWERS ARE WITHIN 300 NM OF THE UPPER LOW. ANOTHER SFC TROUGH CLIPS THE AREA EXTENDING FROM A 1013 MB LOW NEAR 36N67W ALONG 32N69W 30N74W 29N77W. A LONGWAVE UPPER TROUGH IS LOCATED MOSTLY N OF 28N BETWEEN 45W AND 61W. AN ASSOCIATED SFC TROUGH EXTENDS FROM 32N48W 28N54W TO 28N59W. SCATTERED SHOWERS ARE WITHIN 120 NM OF THIS TROUGH AXIS. LARGE SCALE UPPER RIDGING CONTINUES TO DOMINATE MUCH OF THE CENTRAL AND EASTERN ATLC WATERS ANCHORED FROM ITS HIGH CENTER NEAR 20N33W. PLENTY OF DRY/STABLE AIR ALOFT COVERS THE E ATLC OUT TO 45W. ACCORDING TO THE 21 Z SAHARAN AIR LAYER ANALYSIS FROM UW-CIMSS THE LEADING EDGE OF DENSE DUST STRETCHES TO 42W MAINLY N OF 15N. AT THE SURFACE...HIGH PRESSURE IS DOMINATING MUCH OF THE TROPICAL ATLANTIC WATERS ON THE SOUTH AND WEST PORTION OF ITS 1028 MB HIGH OVER THE AZORES AND A 1023 MB HIGH IN THE CENTRAL ATLC NEAR 25N51W. THE OTHER SURFACE FEATURES NOTED ARE OBVIOUSLY T.S CHRIS AFFECTING THE NRN LEEWARD ISLANDS AND THE BROAD TROPICAL WAVE ALONG 33W...SEE MORE INFO ON THESE FEATURES ABOVE. $$ CANGIALOSI