National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXCA62 TJSJ 181628
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1228 PM AST SAT MAY 18 2013

.UPDATE...AT THIS MOMENT SATELLITE IMAGES ARE SHOWING CU LINES
DEVELOPING OVER THE LOCAL ISLANDS AND ACROSS THE CORDILLERA
CENTRAL. NO CHANGES TO THE PREVIOUS FORECAST PACKAGE...STILL
EXPECTING SHOWERS AND THUNDERSTORMS ACROSS THE WESTERN PORTIONS OF
PUERTO RICO.


&&

.DISCUSSION...SEAS MAINLY 5 FEET OR LESS TODAY. EASTERLY TRADE
WINDS WILL GRADUALLY INCREASE BY MID WEEK AS PREVIOUSLY MENTIONED
SURFACE PRESSURE GRADIENT TIGHTENS.


&&

.AVIATION...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.


&&

.MARINE...


&&

.PREV DISCUSSION... /ISSUED 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.
&&

$$

10/23