000 AXNT20 KNHC 172338 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST FRI MAR 17 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. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 4N8W 3N20W 4N30W 5N43W 4N52W. WEAKENING SCATTERED SHOWERS/THUNDERSTORMS ARE WITHIN 75 NM OF THE AXIS BETWEEN 18W-21W. ...DISCUSSION... GULF OF MEXICO... MID/UPPER LEVEL HIGH IS CENTERED NEAR THE ISTHMUS OF TEHUANTEPEC. BROAD RIDGE EXTENDS NORTHWARD AND COVERS ALL BUT THE EXTREME NE GULF. VERY WEAK ILL-DEFINED FRONT EXTENDS ACROSS THE NORTHERN GULF. THE FRONT BECOMES A WARM FRONT OVER THE FAR WESTERN GULF AND IS BETTER DEFINED OVER E TEXAS WHERE IT CROSS THE COAST NEAR FREEPORT. THE EASTERN PORTION OF THE WEAK FRONT IS EXPECTED TO SWEEP ACROSS FLORIDA WITH LITTLE TEMPERATURE CHANGE DURING THE NEXT 24 HOURS. A 1019 MB HIGH IS CENTERED SOUTH OF THE FRONT NEAR 27N87W. BAND OF MID/HIGH LEVEL MOISTURE IS STREAMING EASTWARD WITHIN 180 NM OF LINE FROM 24N97W TO 25N88W. OTHERWISE...MOST OF THE GULF IS COVERED BY A DRY MID-LEVEL ENVIRONMENT. THE UPPER PATTERN IS FORECAST TO CHANGE VERY LITTLE WITH MID/UPPER HIGH REMAINING OVER SE MEXICO. THE ASSOCIATED RIDGE IS EXPECTED TO BUILD A LITTLE OVER THE GULF DURING THE NEXT 24 HOURS. CARIBBEAN SEA... ANTICYCLONIC FLOW AROUND THE MID/UPPER HIGH NEAR THE ISTHMUS OF TEHUANTEPEC COVERS THE FAR NW CARIBBEAN SEA. WEAK UPPER LEVEL TROUGH EXTENDS SW FROM JUST EAST OF JAMAICA ACROSS THE CENTRAL CARIBBEAN TO COSTA RICA AND WESTERN PANAMA. A MID/UPPER LEVEL LOW IS LOCATED ALONG THE TROUGH OVER THE SW CARIBBEAN NEAR 12N83W. THE UPPER LOW IS DIFFICULT TO LOCATE AS IT IS BEING MASKED BY DRY AIR AND SUBSIDENCE THAT COVERS THE ENTIRE CARIBBEAN. EAST OF THIS FEATURE...DIFFLUENT UPPER LEVEL FLOW IS AIDING IN THUNDERSTORM DEVELOPMENT OVER INTERIOR PORTIONS OF COLOMBIA. OVER THE EASTERN CARIBBEAN...MID/UPPER LEVEL SWLY FLOW COVERS THE AREA EAST OF THE TROUGH. AT THE SURFACE...FAIRLY TYPICAL TRADES WINDS ARE BLOWING OVER THE SOUTHERN AND EASTERN CARIBBEAN. PATCHES OF LOW/MID CLOUDS WITH A FEW SHOWERS ARE SEEN OVER PUERTO RICO...HISPANIOLA...AND EASTERN CUBA. LOW CLOUDS AND SHOWERS ARE ALSO LOCATED OVER THE INTERIOR PORTIONS OF CENTRAL AMERICA FROM W PANAMA TO NICARAGUA. WESTERN ATLANTIC OCEAN... BROAD WEAK MID/UPPER LEVEL TROUGH ACROSS THE NE U.S. AND WESTERN ATLANTIC EXTENDS SOUTHWARD TO NEAR 28N WEST OF ABOUT 65W. OVER THE REMAINDER OF THE ATLC W OF 50W THE AREA IS UNDER THE INFLUENCE OF ZONAL WESTERLY FLOW. NEAR THE BASE OF THE BROAD TROUGH...AN AREA OF MODERATE TO STRONG SUBSIDENCE IS MOVING ESE ACROSS FLORIDA AND THE W ATLC N OF 25N W OF 72W. AT THE SURFACE A WEAK COLD FRONT EXTENDS ALONG 32N77W TO NEAR JACKSONVILLE FLORIDA. CENTRAL AND E ATLANTIC OCEAN... BROAD WEAK RIDGE EXTENDS NORTHWARD FROM NEAR 20N40W TO BEYOND 32N35W. DEEP LAYER LOW WELL NORTH OF THE REGION EXTENDS A MID/UPPER LEVEL TROUGH SOUTHWARD THAT COVERS THE FAR EASTERN ATLC N OF 20N E OF 30W. AT THE SURFACE...A WEAKENING FRONT EXTENDS THROUGH 32N40W 28N50W TO NEAR 24N65W. SINCE THE FRONT HAS NO UPPER SUPPORT...IT IS FORECAST TO CONTINUE TO WEAKEN AND DISSIPATE WITHIN THE NEXT 12-18 HOURS. FAIRLY WELL-DEFINED MID/UPPER LEVEL RIDGE EXTENDS EAST TO WEST ACROSS THE TROPICAL ATLC ALONG 7N. SMALL WEAKNESS IS NOTED IN THE RIDGE BETWEEN 25W-30W. AREA OF AFRICAN DUST THAT CONTINUES TO SLOWLY THIN...REMAINS EVIDENT IN LATE AFTERNOON VISIBLE SATELLITE IMAGERY OVER THE TROPICAL ATLC. THE DUST EXTENDS FROM THE ITCZ NORTHWARD TO 20N E OF ABOUT 52W. IT DOES NOT APPEAR THAT THE DUST IS RESTRICTING SURFACE VISIBILITIES ACROSS THE TROPICAL ATLC OR EAST CARIBBEAN. $$ BROWN