Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 020149
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
949 PM AST WED OCT 1 2014

.UPDATE...THE DOPPLER WEATHER RADAR DETECTED MOSTLY ISOLATED TO
SCATTERED SHOWERS ACROSS THE SURROUNDING COASTAL WATERS THIS
EVENING. A THUNDERSTORM ALSO PERSISTED OVER THE WESTERN COASTAL
WATERS. HOWEVER...NO SIGNIFICANT PRECIPITATION WAS DETECTED OVER
LAND AREAS SO FAR THIS EVENING. A WEAK TROPICAL WAVE JUST ACROSS THE
LESSER ANTILLES THIS EVENING WILL CONTINUE TO MOVE WESTWARD
OVERNIGHT. THIS WAVE WILL BRING AN INCREASE IN CLOUDINESS...SHOWERS
AND THUNDERSTORMS ACTIVITY ACROSS THE LOCAL ISLANDS AND SURROUNDING
WATERS ESPECIALLY THURSDAY AFTERNOON. AFRICAN DUST IS SEEN FOLLOWING
THE WAVE ON FRIDAY AND WILL LAST THROUGH THE WEEKEND. THIS WILL
CONTRIBUTE TO A DECREASE IN SHOWER ACTIVITY MUCH AS HAS BEEN SEEN
THE LAST SEVERAL DAYS. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
SPECIALLY ACROSS WESTERN AND INTERIOR SECTIONS OF PUERTO RICO DURING
THE AFTERNOON WILL RETURN TO THE AREA IN EASTERLY FLOW BEGINNING
NEXT WEEK. NO SIGNIFICANT WEATHER EVEN IS EXPECTED AT LEAST UNTIL
THE END OF NEXT WEEK.

&&

.AVIATION...VFR CONDS AT ALL TAF SITE ATTM WITH NO SIG WX
IMPACTS. NO CHG TO PREVIOUS AVIATION DISCUSSION...VFR CONDS FCST FOR
ENTIRE PRD WITH PSBL VCSH/SHRA OR ISOLD TSRA BETWEEN 02/18Z-02/21Z
VCTY OF TJBQ AND TJMZ. PSBL BRIEF MTN TOP OBSC OVER THE W INTERIOR
PR. RECENT UPPER AIR DATA AND FCST SUGGESTS LGT WNDS 5-15 KTS BLO
FL150...BCMG EASTERLY AND A LITTLE STRONGER ALOFT.

&&

.MARINE...SEAS REMAIN TRANQUIL AND GENERALLY BELOW 5 FEET
EVERYWHERE. WITH LIGHT TO MODERATE WINDS...MANY AREAS WILL
EXPERIENCE 2 TO 3 FOOT SEAS ONLY. 4 FOOT SEAS ARE MOST LIKELY IN
THE SOUTHWEST PORTION OF THE LOCAL CARIBBEAN WATERS.

&&

.PREV DISCUSSION... /ISSUED 224 PM AST WED OCT 1 2014/

SYNOPSIS...AT UPPER LEVELS...A WEAK LOW PRESSURE EAST OF THE
WINDWARD ISLANDS WILL MOVE NORTHWEST TONIGHT AND TOMORROW AND THEN
MOVE SLOWLY NORTH OVER THE WEEKEND INTO EARLY NEXT WEEK. THIS LOW
WILL STAY AT OR EAST OF 60 WEST LONGITUDE. HIGH PRESSURE NORTHWEST
OF THE AREA WILL FADE OVER THE WEEKEND AND REFORM OVER THE WEST
CENTRAL ATLANTIC NEXT WEEK.

AT MID LEVELS...A RIDGE OF HIGH PRESSURE EXTENDS ACROSS THE AREA
FROM A HIGH 1400 MILES EAST NORTHEAST OF SAN JUAN PUERTO RICO.
THIS RIDGE WILL SHIFT NORTH AND THE FOCUS WILL MOVE TO OVER THE
YUCATAN PENINSULA OVER THE WEEKEND. IT THEN RETURNS TO NORTH OF
THE AREA ON MONDAY. THIS WILL RESULT IN WEAK GRADIENTS OVER THE
LOCAL AREA THROUGH NEXT WEEK. MID LEVELS REMAIN VERY DRY THROUGH
MID WEEK NEXT WEEK EXCEPT OVERNIGHT ON THURSDAY WITH A WEAK WAVE PASSAGE.

AT LOWER LEVELS...A LOBE OF THE HIGH PRESSURE OVER THE NORTHEAST
CENTRAL ATLANTIC WILL SHIFT TO JUST NORTH OF THE LOCAL AREA BY
FRIDAY NIGHT. A WEAK TROPICAL WAVE WILL MOVE THROUGH THE AREA ON
THURSDAY OF THIS WEEK. MUCH DRIER AIR WILL FOLLOW THE WAVE ON
FRIDAY AND CONTINUE ACROSS THE AREA UNTIL MONDAY NIGHT. AFTER
WHICH TRADE WIND SHOWERS WILL BE SCATTERED ACROSS THE LOCAL AREA
THE REST OF NEXT WEEK.

DISCUSSION...A FEW SHOWERS BRIEFLY POPPED UP OVER PUERTO RICO
DURING THE MIDDAY HOURS AS TEMPERATURES ROSE INTO THE UPPER 80S
AND LOWER 90S. ONLY LIGHT AMOUNTS WERE INDICATED BY NATIONAL
WEATHER SERVICE DOPPLER RADAR. THE TROPICAL WAVE EXPECTED TO PASS
ON THURSDAY IS JUST EAST OF THE LEEWARD AND WINDWARD ISLANDS NEAR
59 DEGREES WEST LONGITUDE. THE WAVE IS MOVING AT ABOUT 20 KNOTS.
AFRICAN DUST IS SEEN FOLLOWING THE WAVE ON FRIDAY AND WILL LAST
THROUGH THE WEEKEND IN LIGHT CONCENTRATIONS. THIS WILL CONTRIBUTE
TO A MARKED DECREASE IN SHOWER ACTIVITY MUCH AS HAS BEEN SEEN THE
LAST SEVERAL DAYS. SCATTERED SHOWERS WILL RETURN TO THE AREA IN
EASTERLY FLOW BEGINNING NEXT WEEK.

FOR THE BETTER PART OF THE NEXT 7 DAYS THE UPPER LEVEL LOW WILL
MOVE LITTLE AND WILL ALSO GIVE LITTLE OR NO SUPPORT TO ANY
CONVECTION. WITH MID LEVELS PREDOMINANTLY DRY...CONVECTION WILL BE
DIFFICULT TO SUSTAIN. HENCE THE NEXT 7 DAYS AS A WHOLE WILL BE
DRIER THAN NORMAL AND TEMPERATURES WILL BE SEVERAL DEGREES ABOVE
NORMAL ON AVERAGE.

AVIATION...VFR CONDS AT ALL TAF SITES ATTM WITH NO SIG WX
IMPACTS. NO CHG TO PREVIOUS AVIATION DISCUSSION...VFR CONDS FCST FOR
ENTIRE PD WITH PSBL VCSH/SHRA OR ISOLD TSRA BETWEEN 01/18Z-01/21Z
VCNTY OF TJBQ AND TJMZ. PSBL BRIEF MTN TOP OBSC OVER THE W INTERIOR
PR. RECENT UPPER AIR DATA AND FCST SUGGESTS LGT WINDS 5-15 KTS BLO
FL150...BCMG LGT/VRB ABV AND UP TO FL250. FEW DIURNALLY INDUCED
SHALLOW CU LINES QUICKLY STREAMING WNW BTW E PR AND NRN LEEWARDS BUT
NO SIG VERTICAL DVLPMNT EN ROUTE ATTM. FEW -SHRA PSBL WITH CU
STREAMERS.

MARINE...SEAS REMAIN TRANQUIL AND GENERALLY BELOW 5 FEET
EVERYWHERE. WITH LIGHT TO MODERATE WINDS...MANY AREAS WILL
EXPERIENCE 2 TO 3 FOOT SEAS ONLY. 4 FOOT SEAS ARE MOST LIKELY IN
THE SOUTHWEST PORTION OF THE LOCAL CARIBBEAN WATERS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  78  90  77  89 /  10  30  20  20
STT  79  89  79  89 /  50  50  20  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...NONE.
&&

$$

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