Caribbean - Central America Weather

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
218 PM AST FRI APR 15 2016

...INCREASING SHOWERS...THUNDERSTORMS AND POSSIBLE FLOODING
BEGINNING MONDAY FOR PUERTO RICO AND THE U.S. VIRGIN ISLANDS...

.SYNOPSIS...AT UPPER LEVELS...WEAK TROUGHS WILL MOVE THROUGH THE
AREA ON SATURDAY...MONDAY AND WEDNESDAY. AN UPPER LEVEL LOW WILL
REINFORCE THE TROUGHS FROM ABOUT A 1000 MILES NORTH NORTHEAST OF
PUERTO RICO MONDAY AND TUESDAY. AFTER WEDNESDAY THERE WILL BE A
GRADUAL INFLUX OF HIGHER PRESSURE FROM THE SOUTH.

AT MID LEVELS...LOW PRESSURE IN THE WESTERN ATLANTIC WILL HAVE
MORE AND MORE INFLUENCE OVER PUERTO RICO AND THE U.S. VIRGIN
ISLANDS UNTIL WEDNESDAY. THEN HIGH PRESSURE WILL RIDGE INTO THE
CARIBBEAN FROM THE EAST.

AT LOWER LEVELS...A WEAK LOW PRESSURE NORTHEAST OF THE AREA WILL
BE ABSORBED INTO A VIGOROUS LOW IN THE WESTERN ATLANTIC TO ITS
NORTHWEST SATURDAY...MAINTAINING WEAK GRADIENTS AND WINDS. THEN A
STRONGER LOW IN THE WESTERN ATLANTIC ALONG WITH LOW PRESSURE ALONG
THE COASTS OF COLOMBIA AND VENEZUELA WILL CAUSE DEEP SOUTHWEST
FLOW OVER THE CARIBBEAN AND THE LOCAL AREA. IT WILL ALSO HOLD
TROUGHING OVER PUERTO RICO MONDAY AND TUESDAY THAT WILL SHIFT OVER
TO THE U.S. VIRGIN ISLANDS ON WEDNESDAY AND THE LEEWARD ISLANDS ON
THURSDAY. HIGH PRESSURE WILL BUILD OVER THE WESTERN CENTRAL
ATLANTIC THURSDAY THROUGH FRIDAY NIGHT OF NEXT WEEK...CAUSING FLOW
TO BECOME SOUTHEASTERLY.

&&

.DISCUSSION...PUFFY CUMULUS ATTENDED TO PUERTO RICO AND THE U.S.
VIRGIN ISLANDS WHILE SHOWERS PLAYED HOOKY. AND AS OF 1:30 PM AST
NO SHOWERS WERE SEEN IN THE FORECAST AREA ON NWS DOPPLER RADAR.
ANY SHOWERS THAT OCCUR BETWEEN NOW AND SUNDAY NIGHT ARE LIKELY TO
BE SHALLOW AS THE TOP OF THE INVERSION CONTINUES AROUND 7500 FEET.

HIGH PRESSURE AT 700 MB OVER THE TROPICAL ATLANTIC WILL EXTEND
INTO THE CARIBBEAN OVER THE WEEKEND AND PULL A LARGE PLUME OF
MOISTURE OFF OF NORTHERN SOUTH AMERICA AND OVER PUERTO RICO FROM
THE SOUTHWEST BEGINNING LATE SUNDAY AFTERNOON. THIS INFLUX OF
MOIST AIR WILL ALSO BREAK DOWN THE CAPPING THAT HAS KEPT WEATHER
FAIR SO FAR. MOISTURE CONTINUES TO FLOW OUT OF THE CARIBBEAN ON
TUESDAY WITH A FOCUS ON THE VIRGIN ISLANDS AND THE ANEGADA
PASSAGE. THEN MOISTURE CONTINUES OVER THE AREA THROUGH
FRIDAY...BUT DYNAMICS FOR PUERTO RICO ARE MOST FAVORABLE ON MONDAY
AND MORE FAVORABLE FOR THE U.S. VIRGIN ISLANDS ON TUESDAY AND
WEDNESDAY. WHILE THE GFS HAS BEEN FORECASTING THIS FOR SOME TIME
NOW...THE ECMWF IS FORECASTING EVEN MORE MOISTURE. SHOWERS AND
THUNDERSTORMS MOVING FROM THE SOUTHWEST ARE EXPECTED TO FORM IN
THE CARIBBEAN AND MOVE OVER THE AREA BRING HEAVY RAINFALL TO MOST
IF NOT ALL OF THE ISLANDS. FORECASTERS FROM THE INTERNATIONAL
DESK AT THE WEATHER PREDICTION CENTER ALSO CONCUR THAT THE
POTENTIAL FOR FLOODING FROM EXCESSIVE RAINFALL IS PRESENT OVER THE
AREA FROM MONDAY THROUGH WEDNESDAY...BUT HAVE NOT PLACED THEIR
CONFIDENCE IN THE HIGHER VALUES OF THE ECMWF BECAUSE THEY ARE NOT
SURE HOW THE NEW ALGORITHMS IMPLEMENTED IN THE MODEL WILL BEHAVE
IN THIS SCENARIO. NEVERTHELESS EMERGENCY MANAGERS WILL WANT TO
HAVE A CONTINGENCY PLAN IN PLACE FOR THE BEGINNING OF THE WEEK
NEXT WEEK FOR THE HEAVIEST RAINS OF THE YEAR SO FAR AND POTENTIAL
FLOODING IN PUERTO RICO AND THE U.S. VIRGIN ISLANDS. IT IS NOT
CLEAR AT THIS TIME HOW LONG THE RAINS WILL LAST. THE MODELS SHOW
VERY HIGH PRECIPITABLE WATER VALUES THROUGH FRIDAY OR SATURDAY OF
NEXT WEEK BUT DYNAMICS WILL GRADUALLY DETERIORATE. CURRENT
THOUGHTS ARE THAT SOME HEAVY RAIN WILL CONTINUE ON AND
INTERMITTENT BASIS THROUGH THE END OF THE WEEK AND LOCALIZED
FLOODING THROUGH THAT TIME CANNOT BE RULED OUT.

&&

.AVIATION...MAINLY VFR CONDITIONS EXPECTED ACROSS ALL TERMINALS
DURING THE NEXT 24 HOURS. LIGHT AND VARIABLE WINDS EXPECTED
OVERNIGHT...INCREASING TO AROUND 10 KT FROM THE EAST-NORTHEAST AFTER
16/13Z...WITH SEA BREEZE VARIATIONS.

&&

.MARINE...A 5-FOOT 12 TO 15 SECOND NORTHEAST SWELL HAS BEEN
PASSING THROUGH BOUY 41044 ABOUT 500 MILES NORTHEAST OF SAN JUAN.
IT SHOULD ARRIVE TONIGHT IN THE NORTHERN U.S. VIRGIN ISLANDS AND
EARLY TOMORROW MORNING ON THE NORTHERN COASTS OF PUERTO RICO.
CURRENTLY THIS IS NOT EXPECTED TO NECESSITATE SMALL CRAFT
ADVISORIES...BUT WILL GENERATE AN ELEVATED RISK OF RIP CURRENTS
AND INCREASED BREAKING WAVES ALONG THE EXPOSED COASTS. CONDITIONS
ARE EXPECTED TO SUBSIDE LATER MONDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 85 77 87 / 10 10 20 20
STT 76 88 76 87 / 10 10 20 30

[cycloneye]

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
455 AM AST SAT APR 16 2016

.SYNOPSIS...WEATHER CONDITIONS ARE EXPECTED TO DETERIORATE EARLY
NEXT WEEK WITH AN INCREASING POTENTIAL FOR FLOODING. MEANWHILE...
CONTINUE TO EXPECT FAIR WEATHER TODAY AND TOMORROW.

&&

.DISCUSSION...MOSTLY CLEAR SKIES PREVAILED OVERNIGHT AND EARLY
THIS MORNING. A FEW SPRINKLES WERE OBSERVED ACROSS THE LOCAL
WATERS. THE COASTAL TEMPERATURES WERE IN THE LOW TO MID 70S AND
WINDS WERE LIGHT AND VARIABLE. UNDER A MID LEVEL CAP INVERSION AND
LIMITED LOW LEVEL MOISTURE... CONTINUE TO EXPECT FAIR WEATHER
CONDITIONS WITH LOCALLY INDUCED AFTERNOON SHOWERS ACROSS CENTRAL
PUERTO RICO THROUGH THE WEEKEND.

A BROAD MID TO UPPER LEVEL TROUGH WILL THEN ESTABLISH ACROSS THE
WESTERN ATLANTIC AND INTO THE NORTHERN CARIBBEAN EARLY NEXT WEEK.
AS THE CAP WEAKENS AND THE TROUGH ESTABLISHES...DEEP TROPICAL
MOISTURE IS EXPECTED TO ADVECT ACROSS THE EASTERN CARIBBEAN FROM
THE SOUTHEAST MONDAY...AND CONTINUE THROUGH MUCH OF NEXT WEEK.
UNDER TROUGH ALOFT AND ASSOCIATED FAVORABLE JET DYNAMICS AS WELL
AS PLENTY OF LOW LEVEL MOISTURE...THERE IS HIGH POTENTIAL FOR
HEAVY/PERSISTENT CONVECTION LATE MONDAY MORNING AND TUESDAY.

BASED ON LATEST GUIDANCE...THE HIGHEST CHANCE FOR HEAVY RAINFALL
ACROSS PUERTO RICO...BUT ESPECIALLY THE EASTERN HALF OF THE
ISLANDS...IS EXPECTED ON LATE MONDAY MORNING/AFTERNOON. ACROSS
THE U.S. VIRGIN ISLANDS...PERIODS OF HEAVY RAINFALL ARE EXPECTED
BOTH DAYS...MONDAY AND TUESDAY. WIDESPREAD AREAS OF URBAN AND
SMALL STREAM FLOODING AS WELL AS LOCALIZED FLASH FLOODING IS
POSSIBLE. CONTINUE TO MONITOR THE EVOLUTION OF THIS PATTERN...
EMERGENCY MANAGERS WILL WANT TO HAVE A CONTINGENCY PLAN IN PLACE
FOR THE BEGINNING OF THE WEEK DUE TO INCREASING POTENTIAL FOR
FLOODING.

ALTHOUGH MOISTURE WILL CONTINUE TO PERSIST MUCH OF THE WEEK...
THERE IS A LACK OF DYNAMICS AS THE TROUGH MOVES AWAY ON
WEDNESDAY. THEREFORE...WEDNESDAY THROUGH THE END OF THE WEEK...
PERIODS OF SHOWERS WILL CONTINUE...BUT INTENSITY AND COVERAGE
SHOULD DECREASE.

&&

.AVIATION...VFR CONDITIONS EXPECTED ACROSS ALL TERMINALS DURING
THE NEXT 24 HOURS. LIGHT AND VARIABLE WINDS EXPECTED UNTIL
16/13Z. WINDS WILL THEN INCREASE A LITTLE TO 5-10KT BUT DIRECTION
WILL VARY BY LOCATION WITH A STRONG SEA BREEZE INFLUENCE. SLIGHT
CHANCE OF SHRA OVER THE VICINITY OF TJPS AND TJMZ AFTER
16/17Z...LITTLE TO NO SHRA EXPECTED ELSEWHERE THROUGH THE FORECAST
PERIOD.

&&

.MARINE...A SMALL SWELL WILL CONTINUE TO AFFECT THE LOCAL WATERS
TODAY INCREASING THE RIP CURRENT DEVELOPMENT ACROSS THE NORTH
COAST OF THE ISLANDS FROM TIME TO TIME. A LARGE LONG PERIOD NNE
SWELL IS FORECAST TO AFFECT THE ATLANTIC WATERS ON MONDAY. SEAS
UP TO 5 FEET AND WINDS AROUND 10 KNOTS TODAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 77 86 77 / 10 20 20 40
STT 88 76 88 76 / 10 20 30 40

[cycloneye]

[HurricaneFan]

The GFS looks like it's forecasting a little less rain for Tuesday in general than Yesterday.But one thing I noticed is that the GFS forecast is showing Rain rate at a particular time and not accumulation.
What times of the day does 00Z,06Z,12Z and 18Z on the GFS represents?
Does the GFS have maps for forecasting accumulation as well?

[cycloneye]

The GFS looks like it's forecasting a little less rain for Tuesday in general than Yesterday.But one thing I noticed is that the GFS forecast is showing Rain rate at a particular time and not accumulation.
What times of the day does 00Z,06Z,12Z and 18Z on the GFS represents?
Does the GFS have maps for forecasting accumulation as well?

This total accumulated precipitation graphic covers from today thru next Saturday at 06z or 2 AM EDT.Rainfall total over 2 inches are spread over the NE Caribbean.

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
155 PM AST SAT APR 16 2016

.SYNOPSIS...
A MID TO UPPER LEVEL TROUGH IS EXPECTED TO REACH THE LOCAL AREA BY
EARLY NEXT WEEK AND WILL BE REPLACED BY A RIDGE. AT THE
SURFACE...A LOW PRESSURE SYSTEM...OVER THE WESTERN ATLANTIC
OCEAN...WILL SLOWLY SPREAD INTO THE CENTRAL ATLANTIC.

&&

.DISCUSSION...
IN GENERAL...A FAIR WEATHER PATTERN PREVAILED DURING THE DAY
ACROSS THE ARCHIPELAGO OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS.
CLOUDS FORMED OVER THE CORDILLERA CENTRAL LATE IN THE
AFTERNOON...BUT THE DOPPLER RADAR DID NOT DETECT ANY SIGNIFICANT
RAINFALL ACCUMULATION SO FAR OVER LAND. LATER THIS AFTERNOON...A
FEW SHOWERS MAY FORM MAINLY OVER THIS AREA...HOWEVER MUST OF THEM
WILL BE LIGHT AND OF SHORT DURATION. ELSEWHERE...MOSTLY CLEAR
SKIES WITH LITTLE OR NO SHOWER ACTIVITY. FAIR WEATHER CONDITIONS
WILL CONTINUE FOR THE REST OF TODAY AND TOMORROW WITH SOME
ISOLATED CONVECTION OVER THE MOUNTAINS AND WESTERN INTERIOR PUERTO
RICO DURING THE AFTERNOONS.

THE LATEST MODEL GUIDANCE CONTINUES TO INDICATE SOME POTENTIAL
FOR MODERATE TO LOCAL HEAVY RAINFALL ACTIVITY THAT COULD LEAD TO
SOME URBAN AND SMALL STREAM FLOODING MAINLY ACROSS EASTERN PUERTO
RICO MONDAY AND TUESDAY. HOWEVER...THE BEST CHANCE FOR HEAVY
RAINFALL AND THUNDERSTORMS SEEMS TO BE IN AND AROUND THE U.S.
VIRGIN ISLANDS...ESPECIALLY SAINT CROIX...WHERE THE GFS HAS A
BETTER SURFACE CONVERGENCE WITH DIFFLUENCE ALOFT. ALSO...THE GFS
TENDS TO DISSIPATE THE CAP BY MONDAY AND THE LOW-MID LEVEL
STABILITY TREND SEEMS TO BE AROUND THE NORMAL CLIMATOLOGICAL
VALUES FOR THIS MONTH. ALL THESE INGREDIENTS ARE FAVORABLE FOR THE
FORMATION OF SHOWERS AND THUNDERSTORMS ACROSS THE REGION.

EMERGENCY MANAGERS WILL WANT TO CLOSELY FOLLOWED THE EVOLUTION OF
THE WEATHER CONDITIONS TO BE READY IN CASE FLOODING IS EXPECTED. A
CONTINGENCY PLAN MAY BE NEEDED FOR THE BEGINNING OF THE UPCOMING
WEEK.

ENOUGH MOISTURE ADVECTION IS EXPECTED TO CONTINUES THROUGH MUCH
OF THE UPCOMING WEEK TO PRODUCE PERIODS OF SHOWERS AND POSSIBLE
THUNDERSTORMS...BUT INTENSITY AND COVERAGE SHOULD DECREASE AFTER
TUESDAY. STAY TUNED IN ORDER TO FOLLOWED THE EVOLUTION OF THE
UPCOMING WEATHER CONDITIONS.

&&

.AVIATION...
FAIR WEATHER IS EXPECTED WITH VFR CONDITIONS PREVAILING
AT ALL TAF SITES THRU 17/16Z. OBSCURATIONS OF THE HIGHEST MOUNTAINS
IN PUERTO RICO ARE EXPECTED TIL 16/22Z WITH SOME SHRA AND MVFR CIGS
VCNTY. WINDS ARE EASTERLY 10 KT OR LESS AT THE SFC WITH SEA BREEZE
INFLUENCES DOMINATING. WINDS ALF BECOME WESTERLY AROUND FL075 AND
INCREASE GRADUALLY TO 50 KNOTS AT FL260 AND TO A MAXIMUM OF 85 KNOTS
AT FL450.

&&

.MARINE...
A SMALL SWELL WILL CONTINUE TO AFFECT THE LOCAL WATERS
FOR THE REST OF TODAY. AS A RESULT...THE RISK OF RIP CURRENTS IS
EXPECTED TO INCREASE ACROSS THE NORTH COAST OF THE ISLANDS FROM
TIME TO TIME. MARINERS CAN EXPECT SEAS UP TO 5 FEET AND WINDS
AROUND 10 KNOTS THE REST OF TODAY. A LARGE LONG PERIOD NNE SWELL
IS FORECAST TO AFFECT THE ATLANTIC WATERS ON MONDAY THROUGH
TUESDAY. STAY TUNED FOR ADDITIONAL INFORMATION REGARDING THIS
SWELL.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 74 86 77 84 / 20 20 40 60
STT 78 88 76 84 / 20 30 40 60

[cycloneye]

Here is the latest from the San Juan NWS and the GFS accumulated precipitation totals at 12z run.It shows over 4 inches of rain for the Leeward Islands and U.S VI / BVI and lesser amounts for Puerto Rico from Monday thru Saturday.Let's continue to watch how this evolves.

[HurricaneFan]

So it looks like up to 10 inches of Rain is forecasted for the open ocean.That is pretty interesting.
Why is that?

[cycloneye]

So it looks like up to 10 inches of Rain is forecasted for the open ocean.That is pretty interesting.
Why is that?

Trough amplifies east of islands.

[cycloneye]

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE SAN JUAN PR
532 AM AST SUN APR 17 2016

.SYNOPSIS...A MID TO UPPER LEVEL TROUGH WILL CONTINUE TO SHIFT
SOUTHEAST ACROSS THE WESTERN AND CENTRAL ATLANTIC EARLY THIS
WEEK...WHILE WEAKENING. A LIGHT EASTERLY WIND FLOW WILL CONTINUE
TO PREVAIL ACROSS THE FORECAST AREA THROUGH THE REST OF THE
WEEKEND...BECOMING EAST TO NORTHEASTERLY ON MONDAY. LOW LEVEL
MOISTURE CONVERGENCE IS EXPECTED TO REMAIN SOUTH AND EAST OF
PUERTO RICO THROUGH AT LEAST LATE WEDNESDAY.

&&

.DISCUSSION...FREE-RAIN CONDITIONS AND MOSTLY CLEAR SKIES PREVAILED
OVERNIGHT AND EARLY THIS MORNING. THE COASTAL TEMPERATURES WERE IN
THE MID 70S AND WINDS WERE LIGHT AND VARIABLE. A GENERALLY FAIR
AND MAINLY STABLE WEATHER PATTERN IS EXPECTED TO PREVAIL TODAY
WITH LOCALLY INDUCED SHOWERS ACROSS CENTRAL PUERTO RICO DURING THE
AFTERNOON HOURS.

AS THE CAP INVERSION WEAKENS...A MID TO UPPER LEVEL TROUGH SHIFT
SOUTHEAST ACROSS THE WESTERN AND CENTRAL ATLANTIC...AND A SURFACE
LOW WELL TO OUR NORTH CONTINUES TO PREVAIL...DEEP TROPICAL
MOISTURE IS EXPECTED TO ADVECT ACROSS THE EASTERN CARIBBEAN FROM
THE SOUTHEAST BEGINNING LATE TONIGHT. HOWEVER... BEST LOW LEVEL
MOISTURE CONVERGENCE IS EXPECTED TO REMAIN SOUTH AND EAST OF
PUERTO RICO THROUGH AT LEAST LATE WEDNESDAY. POOL OF MOISTURE
SOUTH AND EAST OF THE AREA WILL THEN RETROGRADE LATE WEDNESDAY AND
THURSDAY...REACHING THE LOCAL ISLANDS BY THE END OF THE WORKWEEK.
ALTHOUGH MOISTURE CONVERGENCE IS EXPECTED TO REMAIN ACROSS THE
CARIBBEAN WATERS AND SAINT CROIX MONDAY THROUGH WEDNESDAY...
ENOUGH MOISTURE IS EXPECTED TO ADVECT ACROSS PUERTO RICO EARLY
THIS WEEK.

BASED ON LATEST GUIDANCE...THE HIGHEST CHANCE FOR SHOWER AND
THUNDERSTORM ACTIVITY IS EXPECTED ACROSS THE CARIBBEAN WATERS AND
SAINT CROIX LATE MONDAY INTO TUESDAY WHERE THE BEST MOISTURE
CONVERGENCE AND UPPER LEVEL DYNAMICS WILL BE LOCATED. THEREFORE...
EXPECT PASSING SHOWERS ACROSS WINDWARD AREAS SUNDAY NIGHT/MONDAY
MORNING. AS LOW LEVEL MOISTURE INCREASES DURING THE DAY ON
MONDAY... FREQUENCY OF SHOWER AND THUNDERSTORM ACTIVITY WILL
INCREASE ACROSS THE CARIBBEAN WATERS AND SAINT CROIX...WITH
LOCALLY INDUCED SHOWERS AND THUNDERSTORMS EXPECTED OVER AND NORTH
OF THE CORDILLERA MONDAY AFTERNOON.

LATE MONDAY INTO TUESDAY...ACTIVITY WILL BE THEN FOCUSED ACROSS
THE CARIBBEAN WATERS AND USVI...SOME OF THESE STORMS WILL REACH
EASTERN PUERTO RICO AT TIMES. MOISTURE AND UPPER LEVEL DYNAMICS
WILL THEN DECREASE LATER ON TUESDAY...AS TROUGH ALOFT MOVES AWAY.
LOW LEVEL MOISTURE AND FAVORABLE UPPER LEVEL DYNAMICS ARE EXPECTED
TO INCREASE ONCE AGAIN BY THE END OF THE WORKWEEK.

ALTHOUGH LATEST MODEL GUIDANCE MAY SUGGEST THAT THE RISK FOR
WIDESPREAD FLOODING HAS DECREASED...THERE STILL POTENTIAL FOR
URBAN AND SMALL STREAM/GUT FLOODING ACROSS SAINT CROIX AND
POSSIBLY EASTERN PUERTO RICO WITH THE HEAVIEST SHOWERS/THUNDERSTORMS.
LOCALIZED FLASH FLOODING WILL NOT BE RULED OUT.

&&

.AVIATION...FAIR WEATHER IS EXPECTED WITH VFR CONDITIONS PREVAILING
AT ALL TAF SITES THROUGH THE FORECAST PERIOD. SHRA MAY DEVELOP OVER
PORTIONS OF THE CORDILLERA CENTRAL AFT 17/18Z...RESULTING IN
MOUNTAIN OBSCURATIONS AND POSSIBLE VCSH AT TJMZ. LIGHT AND VARIABLE
WINDS WILL PREVAIL UNTIL 17/13Z...INCREASING TO AROUND 10KT FROM THE
ESE WITH SEA BREEZE VARIATIONS.

&&

.MARINE...SEAS ARE EXPECTED TO CONTINUE 4-5 FEET THROUGH THE REST
OF THE WEEKEND. WINDS IN GENERAL WILL REMAIN BELOW 10 KNOTS FROM
THE EAST. A LONG PERIOD NORTH TO NORTHWEST SWELL WILL ENTER THE
ATLANTIC WATERS AND MONA PASSAGE ON MONDAY...CREATING HAZARDOUS
SEAS AND LARGE BREAKING WAVES THAT WILL GENERATE LIFE THREATENING
RIP CURRENTS ALONG THE ATLANTIC COASTLINE OF PR AND THE NORTHERN
USVI.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 77 85 75 / 20 40 60 50
STT 86 76 85 74 / 30 40 60 60

[cycloneye]

Not a big rain event now for PR but still for the Leewards.We will see.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
158 PM AST SUN APR 17 2016

.SYNOPSIS...AT UPPER LEVELS...A STRONG JET...WITH CORE VELOCITIES
UP TO 120 KNOTS...WILL MOVE THROUGH THE ATLANTIC WATERS JUST
NORTH OF THE LOCAL AREA IN ASSOCIATION WITH A TROUGH MOVING TOWARD
THE AREA FROM THE NORTHWEST. A MILD RIDGE WILL FOLLOW AFTER
TUESDAY AND CONTINUE THROUGH FRIDAY.

AT MID LEVELS...AT MID LEVELS...A TROUGH WILL DEEPEN OVER
HISPANIOLA TONIGHT THROUGH TUESDAY BUT WILL WEAKEN AS IT PASSES
OVER THE AREA MID WEEK. HIGH PRESSURE WILL SPREAD FROM THE EAST
OVER THE CARIBBEAN DURING THE REST OF THE WEEK.

AT LOWER LEVELS...A FRONTAL BOUNDARY APPROACHES FROM THE NORTH
NORTHWEST...WHILE MOISTURE INCREASES FROM THE SOUTH...INCREASING
SHOWERS AND THE CHANCE OF THUNDERSTORMS FOR MUCH OF THE REST OF
THE WEEK.

&&

.DISCUSSION...PREVIOUS SUPPLEMENTAL DISCUSSION HOLDS...THE LATEST
GFS AND NAM MODEL RUNS HAVE ALL FOLLOWED THE PATTERN THAT THEY
HAVE BEEN DEMONSTRATING FOR THE LAST 72 HOURS IN THAT THEY HAVE
GREATLY OVER-ESTIMATED THE CHANCE OF SHOWERS OVER PUERTO RICO AND
INDEED MUCH OF THE LOCAL WATERS SURROUNDING PUERTO RICO AND THE
U.S. VIRGIN ISLANDS. ALTHOUGH MOISTURE IS INCREASING...LOW LEVEL
MOISTURE IS STILL NOT APPARENT...EITHER OVER THE LOCAL FORECAST
AREA OR OVER THE CARIBBEAN UPSTREAM TO SOUTH AMERICA. ALSO
THUNDERSTORMS ARE NOT PRESENT OVER THE CARIBBEAN AS WOULD BE
EXPECTED IF AN UNSTABLE AND VERY MOIST AIR MASS WERE ENROUTE TO
THE AREA. CLOSE EXAMINATION OF THE GFS MODEL CROSS SECTIONS ALSO
SHOWS THAT THE MAJORITY OF THE MOISTURE FORECAST WILL BE CONTAINED
IN MID CLOUD LAYERS EXPECTED TO INCREASE OVER THE AREA DURING THE
NEXT 24 HOURS. MOISTURE INCREASES AT THESE LEVELS AFTER MONDAY
EVEN AS THE HEIGHT OF THE GOOD MOISTURE DECREASES FROM A PEAK OF
AROUND 20 THOUSAND FEET ON 18/18Z OVER PUERTO RICO AND A PEAK OF
AROUND 25 THOUSAND FEET JUST SOUTH OF CHARLOTTE AMALIE. THE LATEST
GFS...THE 17/12Z RUN...IS FORECASTING STRONG UPPER LEVEL
DIVERGENCE MAXIMUMS AT 12Z OVER NORTH CENTRAL PUERTO RICO WITH A
WIDE SWATH OF MODERATE DIVERGENCE OVER MUCH OF OUR CARIBBEAN
WATERS IN RESPONSE TO A STRENGTHENING JET TO OUR NORTH AT 21.5
DEGREES NORTH BEFORE MUCH OF THE MOISTURE ARRIVES. BUT THE AXIS OF
THIS DIVERGENCE SHIFTS TO SOUTH OF SAINT CROIX AND SOUTH OF OUR
FORECAST AREA BY 18Z...LEADING TO CONVERGENCE OVER PUERTO RICO.

WHILE SOME SHOWERS MAY ACTUALLY MATERIALIZE OFFSHORE TO THE
SOUTHWEST OF PUERTO RICO EARLY MONDAY MORNING RAINFALL AMOUNTS
WILL HARDLY BE ENOUGH TO CREATE FLOODING SO EARLY.
THEN...LATER...CLOUDS WILL BLOCK MUCH OF THE SUNLIGHT NECESSARY TO
CREATE LOCAL INSTABILITY FOR THUNDERSTORMS...MEANING THAT VERY
HEAVY SHOWERS NECESSARY FOR WIDESPREAD FLOODING MAY ONLY BE
ISOLATED OCCURRENCES NOT CAPABLE OF DOING MORE THAN CREATING URBAN
AND SMALL STREAM FLOODING IN LOCALIZED INTERIOR AREAS.

ALSO THE ECMWF APPEARS TO BE FOLLOWING A SIMILAR FORECASTING
TREND. THIS MODEL HAS TONED DOWN RAIN AMOUNTS EXPECTED FOR MONDAY
AND TUESDAY AND SHIFTED THEM SOUTH OF SAINT CROIX.

&&

.HYDROLOGY...WITH MODELS FORECASTING THE BEST RAINS OVER THE
CARIBBEAN SOUTH AND SOUTHEAST OF OUR AREA OF RESPONSIBILITY AND
MODELS CONTINUING TO OVER-FORECAST TODAY WHERE LITTLE OR NO SIGNIFICANT
SHOWERS HAVE BEEN OCCURRING (UP THROUGH 2PM AST)...WILL NOT ISSUE
A FLASH FLOOD WATCH AT THIS TIME FOR PUERTO RICO OR THE U.S.
VIRGIN ISLANDS. SOME URBAN AND SMALL STREAM FLOODING MAY BE
POSSIBLE ACROSS INTERIOR AND NORTHEAST PUERTO RICO MONDAY
AFTERNOON...BUT IT SHOULD BE MANAGEABLE.

&&

.AVIATION...MAINLY VFR EXPECTED OVERNIGHT. HOWEVER...SHRA INCREASES
ACROSS THE CARIBBEAN WATERS/ANEGADA PASSAGE BY 18/10Z...AND ISLD
TSRA AFTER 18/16Z. IMPACTING FIRST THE LEEWARD/USVI TERMINALS AND
THEN THE PR TERMINALS ON MONDAY AFTERNOON. LIGHT AND VARIABLE WINDS
THRU THE OVERNIGHT HOURS...INCREASING TO AROUND 10 KT FROM THE NE BY
18/13Z.


&&

.MARINE...SEAS AT 41043 HAVE BEEN RUNNING AROUND 5 FEET WITH THE
DOMINANT PERIOD OF 12 TO 15 SECONDS. THE LOW NORTH OF THE FORECAST
AREA IS STILL STRENGTHENING AND SEAS AT BOUY 41048 ABOUT 948 MILES
NORTH NORTHWEST OF SAN JUAN HAVE RISEN TO 15 FEET WITH A PERIOD
OF 8 SECONDS WITH AN 8 FOOT SWELL WITH A PERIOD OF ALMOST 15
SECONDS. THE CENTER OF THIS SWELL TRAIN HOWEVER WILL ARRIVE WEST
OF US SOMETIME LATE MONDAY NIGHT. THIS IS ENOUGH TO CREATE A HIGH
RISK OF RIP CURRENTS AND HIGH SURF ALONG SOME NORTH FACING BEACHES
OF PUERTO RICO...BUT NOT BEFORE LATE MONDAY. CURRENT FORECAST
APPEARS ON TRACK. SMALL CRAFT ADVISORIES FOR SEAS GREATER THAN 7
FEET IN THE ATLANTIC AND SOME PASSAGES BY MONDAY NIGHT ARE
EXPECTED.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 85 75 85 / 10 60 50 50
STT 76 85 74 85 / 10 50 60 60

&&

[msbee]

Unfortunately I think this rain event is going to be a bust

[cycloneye]

Unfortunately I think this rain event is going to be a bust

Hopefully not but instability is not great at this time so unless that goes up it may bust so let's see what happens.

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
516 AM AST MON APR 18 2016

.SYNOPSIS...UPPER LEVEL TROUGH WILL MOVES NORTH OF THE AREA LATER
TODAY AND INTO TUESDAY. THIS TROUGH AND A STRONG JET STREAM WILL
CREATE UNSTABLE ATMOSPHERIC CONDITIONS ACROSS THE REGION TODAY
INTO WEDNESDAY. PERIODS OF SHOWERS WITH THUNDERSTORMS IS
EXPECTED.

&&

.DISCUSSION...INCREASING CLOUDINESS WERE SEEN ACROSS THE LOCAL
ISLANDS OVERNIGHT. SHOWERS AND THUNDERSTORMS WERE STARTING TO
MOVE ACROSS THE CARIBBEAN WATERS...APPROACHING SOUTH CROIX IN THE
U.S. VIRGIN ISLANDS. ALL THIS MOISTURE WILL MOVE NORTH THROUGHOUT
THE DAY AND WILL AFFECT THE U.S VIRGIN ISLANDS FIRST AND PUERTO
RICO LATER THIS MORNING INTO THIS AFTERNOON. ACTIVE WEATHER IS
EXPECTED TODAY...AS DEEP LOW LEVEL MOISTURE COMBINED WITH AN UPPER
LEVEL TROUGH TO PRODUCE GOOD CHANCE FOR SHOWERS AND THUNDERSTORMS.
BETTER MOISTURE WILL ARRIVE TO THE LOCAL AREA LATE THIS AFTERNOON
INTO TONIGHT. A RATHER MOIST AND WET PATTERN IS EXPECTED TO
CONTINUE THROUGH AT LEAST WEDNESDAY.

&&

.AVIATION...CLOUDINESS AND SHRA WILL CONTINUE TO INCREASE ACROSS
THE CARIBBEAN WATERS/ANEGADA PASSAGE THROUGH THE MORNING HOURS.
ISLD TSRA EXPECTED ACROSS THE AREA AFT 18/15Z...AND MAY AFFECT
JSJ/IST/ISX AND LEEWARD TERMINALS...RESULTING IN PERIODS OF MVFR
CONDS. LIGHT NE WINDS CONTINUE.


&&

.MARINE...HIGH RISK OF RIP CURRENT IS EXPECTED ACROSS THE NORTH
FACING BEACHES OF PUERTO RICO AND ALSO ACROSS THE NORTHERN U.S.
VIRGIN ISLANDS THROUGH AT LEAST MID WEEK. A NORTHERLY SWELL IS
EXPECTED TO REACH THE ATLANTIC OFFSHORE WATERS THIS AFTERNOON. AS
A RESULT A SMALL CRAFT ADVISORY IS IN EFFECT. FOR ADDITIONAL
INFORMATION GO TO THE MARINE PRODUCTS ISSUED BY WFO SAN JUAN...
MWWSJU...AND CFWSJU.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 74 84 74 / 60 50 50 40
STT 85 75 85 75 / 50 60 60 40

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
224 PM AST MON APR 18 2016

.SYNOPSIS...THE CORE OF A 120 KNOT JET JUST NORTH OF PUERTO RICO
AT 22 DEGREES NORTH WILL RAPIDLY DEPART THE AREA TO THE EAST
NORTHEAST. THE ACCOMPANYING TROUGH WILL PASS THROUGH THE AREA ON
TUESDAY. A RIDGE WILL BUILD OVER THE AREA LATE IN THE WEEK. A
SHORT WAVE TROUGH WILL PASS THROUGH LATE SATURDAY OF NEXT WEEK.

AT MID LEVELS...LONG WAVE TROUGHING WILL CONTINUE IN THE WESTERN
ATLANTIC WELL NORTH OF THE AREA...BUT LOW PRESSURES WILL ROTATE
THROUGH THAT AREA UNTIL FRIDAY NIGHT WHEN A RIDGE BUILDS OVER
MUCH OF THE WESTERN ATLANTIC. HIGH PRESSURE WILL BUILD OVER THE
CARIBBEAN FROM THE EAST LATER THIS WEEK. THE CORE OF THE MID LEVEL
MOISTURE WILL REMAIN SOUTHEAST FOR MUCH OF THE WEEK. OVER THE WEEK
END MOST OF THE MOISTURE WILL BE NORTHEAST OF THE AREA. BUT PUERTO
RICO AND THE U.S. VIRGIN ISLANDS SEE ONLY MODERATE MOISTURE AT MID
LEVELS UNTIL THE WEEKEND.

AT LOWER LEVELS...HIGH PRESSURE WILL SLOWLY BUILD OVER THE
WESTERN ATLANTIC DURING THE WEEK INCREASING THE TRADE WINDS. A
COLD FRONT IS SLOWLY EDGING TOWARD THE FORECAST AREA FROM THE
NORTHWEST WHILE A POOL OF MOISTURE IS ENCROACHING ON THE AREA FROM
THE SOUTH SPREADING INCREASED CHANCES OF SHOWERS OVER THE AREA.
THE BEST MOISTURE OVER THE AREA IS EXPECTED TONIGHT. MOISTURE
WILL REMAIN GOOD THROUGH THE WEEKEND.

&&

.DISCUSSION...STREAMS OF SHOWERS BEGAN FORMING OVER PUERTO RICO
DURING THE EARLY AFTERNOON WITH SOME HEAVY...BUT FAST-MOVING
SHOWERS. SHOWERS FORMED FIRST OUT OF RIO GRANDE...JUNCOS AND SAN
LORENZO AND THEN OVER THE CORDILLERA CENTRAL OF SOUTHWEST PUERTO
RICO. SCATTERED SHOWER REMAINED OVER MUCH OF THE SOUTHEAST
PORTION OF THE LOCAL CARIBBEAN WATERS. ALL SHOWERS WERE MOVING AT
A LITTLE MORE THAN 30 KNOTS FROM THE SOUTHWEST. SHOWERS ARE
EXPECTED TO INCREASE NOW THAT THE SOUNDING HAS LOST ITS MARINE
INVERSION...BETTER MOISTURE IS ENCROACHING FROM THE SOUTH AND THE
BEST DIVERGENCE OF AT LEAST THE NEXT 72 HOURS IS OVER PUERTO
RICO...AND THE CARIBBEAN SOUTHEAST OF THE AREA. ONCE THE JET
DEPARTS THE AREA TONIGHT DYNAMICS WILL DECREASE AND MOISTURE
MIGRATION WILL STALL. THE GFS SHOWS THAT EXCELLENT MOISTURE WILL
CONTINUE OVER THE SOUTHEAST PORTION OF OUR FORECAST AREA THROUGH
TUESDAY...BUT THIS MAY NOT BE ENOUGH TO INITIATE FLOODING. UP TO
18/1630Z ONLY 0.04 INCHES OF RAIN HAVE FALLEN AT THE AIRPORT IN
FREDERIKSTED...AND SHOWERS ARE WIDELY SCATTERED UP STREAM.
SIGNIFICANT CLOUDINESS WILL ALSO KEEP CONVECTION TO A MINIMUM.
SHOWERS SHOULD INCREASE OVER NIGHT AT LEAST UNTIL 19/06Z AND THEN
BEGIN TO TAPER OFF. TUESDAY THROUGH FRIDAY SHOWERS ARE STILL
EXPECTED AS MOISTURE REMAINS FAVORABLE...BUT MID LEVELS DO NOT
MOISTEN APPRECIABLY FROM CURRENT LEVELS UNTIL SATURDAY. CONFIDENCE
IS MODEST...THOUGH...AS THE GFS HAS NOT SHOWN CONSISTENT
FORECASTS AFTER AROUND 72 HOURS.

&&

.AVIATION...CLOUDINESS AND SHOWERS WITH POSSIBLE TSRA WILL INCREASE
ACROSS THE LOCAL FLYING AREA FOR THE NEXT 24 HOURS. THIS ACTIVITY
WILL RESULT IN PERIODS OF MVFR OR EVEN IFR CONDITIONS ACROSS THE
LEEWARD AND USVI TAF SITES. PERIODS OF MVFR CONDITIONS OR EVEN IFR
CONDITIONS ARE ALSO POSSIBLE ACROSS TJPS AND TJSJ. LATEST TJSJ
SOUNDING INDICATED A LIGHT AND VARIABLE WIND FLOW FROM THE SURFACE
TO AROUND 7K FEET...BECOMING WESTERLY AND STRONGER ABOVE 7K FEET.
LATEST SOUNDING INDICATED A WESTERLY WIND UP TO 85 KNOTS AT 35K FEET
WITH STRONGER WINDS ABOVE THAT LEVEL.

&&

.MARINE...SEAS HAVE REACHED NEARLY 7 FEET AT RINCON THIS MORNING
BUT NO FURTHER SO FAR. THE OUTER BUOY DROPPED ABRUPTLY TO JUST
BELOW 7 FEET FROM NEARLY 8 FEET...SEAS WHICH CONSIST MOSTLY OF 13
TO 15 SECOND SWELL...ARE EXPECTED TO RISE AGAIN EARLY TONIGHT AND
THEN SUBSIDE UNSTEADILY AFTERWARD. BUOY READINGS SUGGEST THAT
AREAS OF NORTH-FACING COASTS OF PUERTO RICO HAVE SEEN 10 FOOT
BREAKING WAVES...ALTHOUGH NO REPORTS HAVE BEEN RECEIVED AND BUOY
41053 IS STILL OUT OF SERVICE.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 74 84 74 84 / 50 50 40 40
STT 75 85 75 86 / 60 60 40 40

[cycloneye]

The latest precipitation accumulation totals until next Saturday are between 4-6 inches for some of the islands in the Leewards.

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
623 AM AST TUE APR 19 2016

.SYNOPSIS...AT UPPER LEVELS...A WEAK TROUGH WILL PASS THROUGH THE
AREA TODAY WITH A RIDGE MOVING INTO THE AREA ON THURSDAY. A
MODERATE TO STRONG JET WILL CONTINUE NORTH OF THE AREA BUT WILL
WEAKEN AND SHIFT NORTH TODAY THROUGH FRIDAY.

AT MID LEVELS...AFTER A WEAK TROUGH MOVES THROUGH THE AREA TONIGHT
GRADIENTS WILL RELAX AND HIGH PRESSURE WILL BUILD WEAKLY OVER THE
CARIBBEAN BY THE WEEKEND. SOME MOISTURE AT MID LEVELS WILL
CONTINUE THROUGH THE NEXT 7 TO 10 DAYS. THIS MOISTURE WILL SHIFT
NORTH NEXT WEEK.

AT LOWER LEVELS...THE LOW PRESSURE WHICH DOMINATES MUCH OF THE
ATLANTIC WILL SHIFT NORTH AND HIGH PRESSURES ON BOTH COASTS OF THE
ATLANTIC WILL BUILD OVER THE SUB TROPICS LATER IN THE WEEK. THIS
WILL CAUSE WINDS TO SHIFT TO THE EAST BY FRIDAY AND TO THE
SOUTHEAST OVER THE WEEKEND AND INTO EARLY NEXT WEEK.

&&

.DISCUSSION...SHOWERS CONTINUED OVER THE SOUTHEAST PORTION OF THE
FORECAST AREA OVERNIGHT BUT REMAINED MOSTLY SOUTHEAST OF SAINT
CROIX. A FEW SHOWERS TRANSVERSED PUERTO RICO. OTHER SHOWERS FORMED
IN THE ATLANTIC THAT APPEARED DUE TO THE FRONT MOVING INTO THE
AREA. SHOWER FORMATION IS EXPECTED TO MOVE INTO PUERTO RICO THIS
MORNING AND INTENSIFY DURING THE AFTERNOON HOURS AS MOISTURE AND
THE FRONT AID CONVECTION. STABILITY THEN INCREASES THROUGH LATE
WEDNESDAY NIGHT AND SHOWERS WILL TAPER OFF. THE GFS SHOWS MOISTURE
MOVING BACK OVER THE AREA ON THURSDAY AND THEN THE BEST MOISTURE
WILL BE NORTHEAST OF THE AREA. NEVERTHELESS WE CONTINUE IN AN AREA
OF MOISTURE FOR MOST OF THE NEXT 10 DAYS FOR AT LEAST SCATTERED
SHOWERS AND THUNDERSTORMS POSSIBLE THOUGH ISOLATED THROUGH EARLY
NEXT WEEK. AT THIS TIME RAIN AMOUNTS ARE NOT FORESEEN TO BE
EXCESSIVE...BUT TRAINING SHOWERS OVER PUERTO RICO ARE POSSIBLE AND
MAY GENERATE URBAN AND SMALL STREAM FLOODING.

MODELS SEEM TO BE TAKING THE SOUTHEAST WINDS FORECAST SATURDAY AND
EARLY NEXT WEEK TO HEART AND BELIEVE THAT THE HIGHS FORECAST FOR
THE SAN JUAN GREATER METROPOLITAN AREA ARE BIT TOO WARM...SINCE
SOME CLOUDINESS WILL PERSIST FROM THE HIGHER THAN USUAL MOISTURE.
NEVERTHELESS HIGHS NEAR 90 MAY BE EXPECTED A LITTLE INLAND FROM
THE AIRPORT BY SATURDAY AND WE MAY REACH 90 DUE TO THE SOUTHEAST
WINDS OVER THE AREA BY MONDAY CLOSE TO THE BEACHES.

&&

.AVIATION...CLOUDINESS AND PERIODS OF SHRA WILL CONTINUE ACROSS/EN
ROUTE OF THE FLYING AREA TODAY. MVFR CONDS WILL REMAIN POSSIBLE AT
TJBQ/TJSJ/TJPS AFT 19/15Z...AS SHRA/TSRA DEVELOPS ONCE AGAIN
ACROSS PUERTO RICO. MOUNTAIN OBSCURATIONS EXPECTED. AT LEEWARD AND
USVI TERMINALS...SHRA/TSRA AT TIMES ARE EXPECTED AND THEREFORE
THIS MAY RESULT IN PERIODS OF MVFR OR EVEN IFR CONDS. LIGHT/VAR
WIND FLOW FROM THE SURFACE TO AROUND 3K FEET...BECOMING WESTERLY
AND STRONGER ABOVE 5K FEET.

&&

.MARINE...SEAS PEAKED AT RINCON AT AROUND 8.8 FEET AND HAVE COME
DOWN AT BOTH THE OUTER BUOY AND THE RINCON BUOY SINCE MIDNIGHT.
THIS EVENT WILL CONTINUE FOR SOME TIME BUT SMALL CRAFT ADVISORIES
ARE EXPECTED TO ALL BE DOWN BY THURSDAY MORNING. LOW PRESSURE IN
THE WESTERN AND CENTRAL ATLANTIC CONTINUE TO GENERATE WAVE ACTION
THROUGH SATURDAY. SEAS ARE EXPECTED TO TOP 7 FEET AGAIN BY LATER
THIS WEEK AS ANOTHER SWELL TRAIN MOVES IN TO THE OUTER ATLANTIC
WATERS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 83 74 84 75 / 40 40 30 30
STT 83 74 86 75 / 60 40 30 30

[msbee]

not much rain here in St Maarten, just intermittent showers. certainly not enough to ease the drought or out out our "dump" fire.

[cycloneye]

not much rain here in St Maarten, just intermittent showers. certainly not enough to ease the drought or out out our "dump" fire.

Really not much there? Here in PR,we have received some heavy showers on Monday and is expected that diurnal heating will ignite another round on Tuesday.