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614 FXCA62 TJSJ 180910 AFDSJU AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN JUAN PR 510 AM AST SAT MAY 18 2013 .SYNOPSIS...STRENGTHENING SURFACE HIGH PRESSURE ACROSS THE NORTH CENTRAL ATLANTIC AND JUST NORTH OF THE REGION WILL MAINTAIN A DOMINANT EASTERLY TRADE WIND FLOW ACROSS THE NORTHEASTERN CARIBBEAN FOR THE NEXT SEVERAL DAYS. MID TO UPPER LEVEL TROUGH CONTINUED TO SHIFT EAST NORTHEAST OF AREA. MEANWHILE MID TO UPPER RIDGE EXTENDS NORTHWARDS ACROSS THE REGION FROM THE CARIBBEAN BASIN. THIS OVERALL PATTERN WILL MAINTAIN PREVAILING UPPER LEVEL WESTERLIES THROUGH AT LEAST THE MIDDLE OF THE UPCOMING WEEK. && .DISCUSSION...PREVIOUS TJSJ 19/00Z UPPER AIR SOUNDING AS WELL AS SAT AND GPS DERIVED PWAT/IPW ANALYSIS PRODUCTS ALL SUGGEST A GRADUAL DYING TREND DURING THE PAST 24 HOURS WITH ONLY SHALLOW PATCHES OF LOW LEVEL MOISTURE MOVING ACROSS THE REGIONAL WATERS. LATEST SATELLITE IMAGERY ALSO SHOWED LESSER CLOUD COVER/MOISTURE COMPARED TO RECENT DAYS...WITH SUBTROPICAL JET AXIS NOW RELOCATED EAST OF THE REGION AND OVER THE LESSER ANTILLES. THIS IS PLACED THE FORECAST AREAS IN A FAIRLY DRY AND SUBSIDENT PATTERN ALOFT. EXPECT FAIR AMOUNTS OF SUNSHINE TODAY WITH SOME DIURNALLY INDUCED SHOWER DEVELOPMENT POSSIBLE MAINLY ACROSS PARTS OF THE CENTRAL AND WEST INTERIOR SECTIONS OF PUERTO RICO. ACTIVITY SHOULD HOWEVER BE OF SHORT DURATION AND NOT WIDESPREAD AMOUNTS OF RAINFALL. BY LATE SUNDAY AND INTO MONDAY A SECONDARY SHORT WAVE SHOULD MOVE JUST NORTH OF THE REGION. HOWEVER NO SIGNIFICANT AMOUNTS OF MOISTURE ADVECTION IS APPARENT AT THIS TIME...AS THE UPPER LEVEL WINDS CONTINUE TO SHEAR THE CONVECTION ACROSS THE TROPICAL ATLANTIC AND MAINTAIN MOST OF TROPICAL MOISTURE SOUTH OF THE REGION. BY MID WEEK HOWEVER AND FOR THE REST OF THE UPCOMING WEEK LOOK FOR INCREASING MOISTURE AS LONG WAVE TROUGH WEST OF THE REGION SHOULD BECOME SLIGHTLY AMPLIFIED WEST OF THE AREA. THIS SHOULD LIFT ADDITIONAL TROPICAL MOISTURE NORTHWARDS ACROSS THE REGION. LATEST GFS MODEL CONTINUED TO SUGGEST PWAT VALUES TO INCREASE TO TWO INCHES OR MORE BY THURSDAY AND INTO THE FOLLOWING WEEKEND. THE COMBINATION OF THE AMPLIFYING UPPER TROUGH AND INCREASING MOISTURE WILL MAKE CONDITIONS MORE FAVORABLE AND UNSTABLE...THUS RESULTING IN BETTER CHANCE FOR ENHANCED CONVECTIVE DEVELOPMENT DURING THE LATTER PART OF THE WEEK. && .AVIATION...MOSTLY VFR COND ARE EXPECTED AT ALL TAF SITES UNTIL 18/16Z. MVFR/PSBL BRIEF IFR CONDS WILL REMAIN LIKELY BETWEEN 18/17Z-18/21Z ALONG THE CORDILLERA CENTRAL AND ACROSS TJMZ IN AREAS OF +SHRA/TSRA. MTN TOPS MAY BE OBSCURED OVER WRN INTERIOR OF PR. FOR THE NORTHERN LEEWARD ISLANDS...MAINLY VFR CONDS ARE EXPECTED. PREVIOUS 18/ 00Z TJSJ SOUNDING INDICATES MAINLY EAST WINDS AT 20 KNOTS OR LESS UP TO 3 KFT...BECOMING LIGHT AND VARIABLE BTW 3-20KFT AND THEN NORTHWESTERLY AND STRONGER ALOFT. && .MARINE...FAIRLY TRANQUIL SEAS OVERALL FOR THE NEXT SEVERAL DAYS...WITH SEAS MAINLY 5 FEET OR LESS TODAY. EASTERLY TRADE WINDS WILL GRADUALLY INCREASE BY MID WEEK AS PREVIOUSLY MENTIONED SURFACE PRESSURE GRADIENT TIGHTENS. && .PRELIMINARY POINT TEMPS/POPS... SJU 86 76 87 77 / 20 20 20 20 STT 86 76 87 78 / 10 30 30 30 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...NONE. VI...NONE. COASTAL WATERS...NONE. && $$ 72/09