Re: Caribbean - Central America Weather
Posted: Wed May 20, 2015 4:38 pm
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
403 PM AST WED MAY 20 2015
.SYNOPSIS...BROAD UPPER TROUGH CONTINUED NORTH OF THE REGION
WITH SEVERAL SHORT WAVE PERTUBATIONS PROPAGATING EASTWARD ACROSS
THE WEST AND CENTRAL ATLANTIC. RIDGE OF HIGH PRESSURE EXTENDS
NORTHWARDS ACROSS THE FORECAST AREA FROM THE EASTERN CARIBBEAN.
THIS OVERALL PATTERN WILL MAINTAIN A WESTERLY WIND FLOW ALOFT
THROUGH THE END OF THE WEEK. SURFACE HIGH PRESSURE RIDGE EXTENDS
OVER THE SOUTHWEST ATLANTIC...WHILE A WEAK TROUGH CONTINUED TO
SHIFT WESTWARD ACROSS THE EASTERN CARIBBEAN.
&&
.DISCUSSION...THE SURGE OF MOISTURE ACCOMPANYING THE SURFACE TROUGH
MOVING ACROSS THE REGION...ALONG WITH LOCAL AND DIURNAL EFFECTS
AND GOOD VENTILATION ALOFT...AIDED IN THE CONVECTIVE DEVELOPMENT
TODAY. SOME SHOWERS AND THUNDERSTORM PRODUCED MODERATE TO LOCALLY
HEAVY RAINFALL WITH DANGEROUS CLOUD TO GROUND LIGHTING OVER PARTS
OF THE EAST INTERIOR SECTIONS OF PUERTO RICO AS WELL AS OVER PARTS
OF THE SAN JUAN METRO AREA. THIS LEAD TO URBAN AND SMALL STREAM
FLOODING IN SOME AREAS. SMALL CLUSTERS OF SHOWERS WERE ALSO
OBSERVED IN AND AROUND SOME OF THE U.S. VIRGIN ISLANDS BUT NO
SIGNIFICANT FLOOD PROBLEMS WAS OBSERVED OR REPORTED. EXPECT THE
SHOWER AND THUNDERSTORM ACTIVITY TO SLOWLY DIMINISH OVER LAND JUST
AFTER SUNSET WITH A GRADUAL CLEARING OVER LAND THEREAFTER.
DURING THE OVERNIGHT HOURS AND THROUGH THURSDAY...LOW LEVEL MOISTURE
ADVECTION EXPECTED TO GRADUALLY INCREASE OVER THE REGION WITH PRECIPITABLE
WATER APPROACHING TWO INCHES BY THURSDAY AFTERNOON. THE 20/12Z TJSJ
UPPER AIR SOUNDING...AND MIMIC TPW PRODUCT ALSO CONFIRMED INCREASING
LOW LEVEL MOISTURE ADVECTION. LATEST GFS MODEL GUIDANCE INITIALIZED
WELL AND CONTINUE TO SUGGEST GOOD POTENTIAL FOR ADDITIONAL CONVECTIVE
ACTIVITY ACROSS THE ISLANDS AND PORTIONS OF THE COASTAL WATERS ON
THURSDAY. UPPER LEVEL DIVERGENCE OVER THE AREA BY THURSDAY AFTERNOON
ALONG WITH LOCAL AND DIURNAL EFFECTS WILL PRODUCE PERIODS OF ENHANCED
AFTERNOON CONVECTION. THE PREVAILING EASTERLIES WILL ASLO BRING PERIODS
OF SHOWERS TO PARTS OF THE EAST COASTAL SECTIONS OF THE ISLANDS...
ESPECIALLY EASTERN PUERTO RICO DURING THE EARLY MORNING HOURS.
A GRADUAL DRYING TREND IS SO FAR FORECAST BY FRIDAY AND INTO THE
WEEKEND. MID TO UPPER LEVEL HIGH PRESSURE RIDGE WILL BUILD ACROSS
THE REGION AND AID IN SUPPRESSING SIGNIFICANT CONVECTION. IN
ADDITION...MODEL GUIDANCE CONTINUED TO SUGGEST THAT THE SAHARAN
AIR LAYER WILL SPREAD ACROSS THE REGION FROM THE TROPICAL ATLANTIC
OVER THE WEEKEND AND INTO THE EARLY PART OF NEXT WEEK.
&&
.AVIATION...SHRA/TSRA SLOWLY DIMINISHING FOR THE REST OF THE
AFTERNOON INTO THE EVENING. TJMZ AND POSSIBLY TJBQ SHOULD OBSERVE
LIGHT RAIN UNTIL ABOUT 20/23Z. MOSTLY VFR CONDS EXPECTED OVERNIGHT
WITH VCSH ACROSS THE LOCAL TERMINALS EXCEPT TJMZ. WINDS WILL BE
LIGHT AND EASTERLY OVERNIGHT...STRENGTHENING AFTER 21/12Z TO ABOUT
10 TO 15 KTS FROM THE EAST SOUTHEAST WITH SEA BREEZE VARIATIONS.
SHRA/TSRA DEVELOPMENT EXPECTED AGAIN AFTER 21/16Z WHICH WILL LIKELY
AFFECT TJSJ/TJBQ/TJMZ.
&&
.MARINE...WINDS AND SEAS CONTINUED AT 10 TO 15 KNOTS AND 4 FEET
OR LESS RESPECTIVELY. EXPECT FAIRLY TRANQUIL SEAS TO CONTINUE
THROUGH THE END OF THE WEEK.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 77 89 78 90 / 30 40 40 20
STT 77 86 78 87 / 50 50 40 30
NATIONAL WEATHER SERVICE SAN JUAN PR
403 PM AST WED MAY 20 2015
.SYNOPSIS...BROAD UPPER TROUGH CONTINUED NORTH OF THE REGION
WITH SEVERAL SHORT WAVE PERTUBATIONS PROPAGATING EASTWARD ACROSS
THE WEST AND CENTRAL ATLANTIC. RIDGE OF HIGH PRESSURE EXTENDS
NORTHWARDS ACROSS THE FORECAST AREA FROM THE EASTERN CARIBBEAN.
THIS OVERALL PATTERN WILL MAINTAIN A WESTERLY WIND FLOW ALOFT
THROUGH THE END OF THE WEEK. SURFACE HIGH PRESSURE RIDGE EXTENDS
OVER THE SOUTHWEST ATLANTIC...WHILE A WEAK TROUGH CONTINUED TO
SHIFT WESTWARD ACROSS THE EASTERN CARIBBEAN.
&&
.DISCUSSION...THE SURGE OF MOISTURE ACCOMPANYING THE SURFACE TROUGH
MOVING ACROSS THE REGION...ALONG WITH LOCAL AND DIURNAL EFFECTS
AND GOOD VENTILATION ALOFT...AIDED IN THE CONVECTIVE DEVELOPMENT
TODAY. SOME SHOWERS AND THUNDERSTORM PRODUCED MODERATE TO LOCALLY
HEAVY RAINFALL WITH DANGEROUS CLOUD TO GROUND LIGHTING OVER PARTS
OF THE EAST INTERIOR SECTIONS OF PUERTO RICO AS WELL AS OVER PARTS
OF THE SAN JUAN METRO AREA. THIS LEAD TO URBAN AND SMALL STREAM
FLOODING IN SOME AREAS. SMALL CLUSTERS OF SHOWERS WERE ALSO
OBSERVED IN AND AROUND SOME OF THE U.S. VIRGIN ISLANDS BUT NO
SIGNIFICANT FLOOD PROBLEMS WAS OBSERVED OR REPORTED. EXPECT THE
SHOWER AND THUNDERSTORM ACTIVITY TO SLOWLY DIMINISH OVER LAND JUST
AFTER SUNSET WITH A GRADUAL CLEARING OVER LAND THEREAFTER.
DURING THE OVERNIGHT HOURS AND THROUGH THURSDAY...LOW LEVEL MOISTURE
ADVECTION EXPECTED TO GRADUALLY INCREASE OVER THE REGION WITH PRECIPITABLE
WATER APPROACHING TWO INCHES BY THURSDAY AFTERNOON. THE 20/12Z TJSJ
UPPER AIR SOUNDING...AND MIMIC TPW PRODUCT ALSO CONFIRMED INCREASING
LOW LEVEL MOISTURE ADVECTION. LATEST GFS MODEL GUIDANCE INITIALIZED
WELL AND CONTINUE TO SUGGEST GOOD POTENTIAL FOR ADDITIONAL CONVECTIVE
ACTIVITY ACROSS THE ISLANDS AND PORTIONS OF THE COASTAL WATERS ON
THURSDAY. UPPER LEVEL DIVERGENCE OVER THE AREA BY THURSDAY AFTERNOON
ALONG WITH LOCAL AND DIURNAL EFFECTS WILL PRODUCE PERIODS OF ENHANCED
AFTERNOON CONVECTION. THE PREVAILING EASTERLIES WILL ASLO BRING PERIODS
OF SHOWERS TO PARTS OF THE EAST COASTAL SECTIONS OF THE ISLANDS...
ESPECIALLY EASTERN PUERTO RICO DURING THE EARLY MORNING HOURS.
A GRADUAL DRYING TREND IS SO FAR FORECAST BY FRIDAY AND INTO THE
WEEKEND. MID TO UPPER LEVEL HIGH PRESSURE RIDGE WILL BUILD ACROSS
THE REGION AND AID IN SUPPRESSING SIGNIFICANT CONVECTION. IN
ADDITION...MODEL GUIDANCE CONTINUED TO SUGGEST THAT THE SAHARAN
AIR LAYER WILL SPREAD ACROSS THE REGION FROM THE TROPICAL ATLANTIC
OVER THE WEEKEND AND INTO THE EARLY PART OF NEXT WEEK.
&&
.AVIATION...SHRA/TSRA SLOWLY DIMINISHING FOR THE REST OF THE
AFTERNOON INTO THE EVENING. TJMZ AND POSSIBLY TJBQ SHOULD OBSERVE
LIGHT RAIN UNTIL ABOUT 20/23Z. MOSTLY VFR CONDS EXPECTED OVERNIGHT
WITH VCSH ACROSS THE LOCAL TERMINALS EXCEPT TJMZ. WINDS WILL BE
LIGHT AND EASTERLY OVERNIGHT...STRENGTHENING AFTER 21/12Z TO ABOUT
10 TO 15 KTS FROM THE EAST SOUTHEAST WITH SEA BREEZE VARIATIONS.
SHRA/TSRA DEVELOPMENT EXPECTED AGAIN AFTER 21/16Z WHICH WILL LIKELY
AFFECT TJSJ/TJBQ/TJMZ.
&&
.MARINE...WINDS AND SEAS CONTINUED AT 10 TO 15 KNOTS AND 4 FEET
OR LESS RESPECTIVELY. EXPECT FAIRLY TRANQUIL SEAS TO CONTINUE
THROUGH THE END OF THE WEEK.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 77 89 78 90 / 30 40 40 20
STT 77 86 78 87 / 50 50 40 30