Caribbean - Central America Weather

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
256 PM AST THU NOV 17 2011

.DISCUSSION...TROUGH WITH 5H LOWS NEAR 60W AND 50W WERE INITIALIZED
PRETTY WELL BY 12Z GFS. THEY ARE CURRENTLY ENTRAINING DEEPER TROPICAL
MOISTURE WITH THE TROPICAL WAVE APPROACHING FROM THE SOUTHEAST. GFS
SOLUTION IS ACCEPTED IN CONSOLIDATING ALL OF THIS INTO A STRENGTHENING
SYSTEM THAT WILL TURN THE DEEP LAYERED FLOW OVER PR/USVI MORE NORTHEAST
LATE TONIGHT/FRI. THIS WILL ADVECT DRIER AIR TOWARDS LOCAL ISLANDS...
BUT LOW LEVELS WILL CONTINUE MOIST ENOUGH FOR CONTINUED BRIEF AND
QUICKLY MOVING SCATTERED SHOWERS...AND POSSIBLY A BIT GUSTY AS THEY
MIX DOWN 15-20 KNOTS. GENERALLY CHANGED LITTLE IN GRIDS/FORECASTS
EXCEPT RAISED LIKLIHOOD FOR SHOWERS SAT NIGHT IN CONTINUED SHALLOW
NIGHTTIME SHOWERS ON WINDWARD SIDE OF PR AND USVI.

&&

.MARINE...WIND AND WAVES ARE BEHAVING ABOUT AS EXPECTED WITH CONDITIONS
SLIGHTLY IMPROVING IN CLOSE TO SHORE. HOWEVER SEAS CONTINUE IN SMALL
CRAFT CATEGORY WITH WIND TO INCREASE NEXT COUPLE OF DAYS THAT WOULD
GENERATE SOME INCREASING SWELL AGAIN OVER THE WEEKEND.

&&

.AVIATION...VFR CONDS ARE EXPECTED AT ALL TAFS SITES THROUGH THE
FORECAST PERIOD. HOWEVER THE DOMINANT EASTERLY TRADE WINDS WILL
CONTINUE TO STEER INTERVALS OF PASSING SHOWERS AND LOW LEVEL CLDS
WITH BASES BTW 020-030 KFT ACROSS THE FLYING AREA. SHOWERS WITH
FEW-ISOLD TCU/CB WILL BE PRESENT BUT MOST WILL CIRCUMNAVIGABLE.
NO OTHER MAJOR HAZARDS EXPECTED EN ROUTE BETWEEN THE LOCAL ISLANDS
AT THIS TIME. IN ADDITION...THE SHOWERS MAY PRODUCE BRIEF SFC WND
GUSTS OF 25 KTS OR SO AT AND NR SOME OF THE TAF SITES AS THEY PASS
BY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 74 86 74 86 / 40 40 30 20
STT 76 87 72 86 / 50 50 20 20

[msbee]

What is all that convection to the East of us? Should we be expecting bad weather?

[cycloneye]

What is all that convection to the East of us? Should we be expecting bad weather?

All of that relates to a late season tropical wave interacting with an upper trough. The same weather that we have seen in past days in the NE Caribbean will continue with patches of clouds and showers comming out from that,but the whole area will not make it to the Caribbean. What may happen from all of that is that something may try to form NE of the islands but stay out at sea.

[cycloneye]

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
918 PM AST THU NOV 17 2011

.SYNOPSIS...MODERATE NORTHEAST TRADES WILL PREVAIL INTO EARLY NEXT
WEEK. A SFC TROUGH AND AN UPPER LEVEL LOW NORTHEAST OF THE AREA
COULD DEVELOP INTO A SUBTROPICAL OR TROPICAL CYCLONE OVR THE
WEEKEND AND COULD BRING LARGE SWELLS INTO OUR AREA EARLY NEXT
WEEK.

&&

.DISCUSSION...GLOBAL MODELS SHOW SIG DRY AIR ADVECTION OVR THE
NEXT 48 HRS AS LOW LEVEL WINDS BACK MORE TO THE NORTHEAST WITH
PWAT DROPPING TO UNDER AN INCH BY 12Z SAT. 12Z AND 18Z PARALLEL
RUNS OF THE PR3KM NAM MODEL SHOW VERY LITTLE AFTERNOON CONVECTION
NEXT TWO AFTERNOONS AND HAVE BACKED OFF IN POPS SIGNIFICANTLY FOR
THE NEXT TWO DAYS. XPC BEST CHANCES FOR SHOWERS TO BE DURING THE
NIGHT.

SAT NIGHT-SUN...MOISTURE AND INSTABILITY INCREASE AS UPPER LEVEL
TROUGH DIGS ACROSS THE REGION. NORTHEAST TRADES ALSO STRENGTHEN AS
PRES GRADIENT TIGHTENS BETWEEN HIGH PRES TO THE NORTH AND
DEVELOPING CYCLONE TO THE NORTHEAST. XPC SHALLOW CONVECTION TO
BREAK OUT SAT NIGHT/EARLY SUN AND BECOME QUITE NUMEROUS WITH SCT
CONVECTION...POSSIBLY DEEP...REFORMING DURING THE AFTERNOON
ACROSS THE SOUTH COAST. XPC UNSETTLED WEATHER THROUGH MON WITH
CONDITIONS IMPROVING TUE AS TROUGH AXIS PUSHES EAST OF THE AREA
AND MID LEVEL RIDGING BEGINS TO ESTABLISH ACROSS THE AREA FROM THE
WEST.

&&

.AVIATION...VFR CONDITIONS NEXT 48 HRS WITH JUST VCSH. POSSIBLE
MVFR CIGS SAT NIGHT-SUN NORTH COAST AND TIST AS WINDS STRENGTHEN
AND MOISTURE DEEPENS.

&&

.MARINE...SEAS UP TO 7 FT STILL BEING OBSERVED ACROSS AMZ710.
SLIGHT IMPROVEMENT IS XPCD OVR THE NEXT 48 HRS BUT A LARGE SET OF
NORTHEAST SWELLS IS FCST TO IMPACT THE ATLC COASTAL WATERS LATE
SUN-TUE AS PRES GRADIENT TIGHTENS BETWEEN HIGH PRES AND
DEVELOPING CYCLONE NORTHEAST OF THE REGION. SMALL CRAFT AND EVEN
HIGH SURF ADVISORIES MAY BE REQUIRED EARLY NEXT WEEK.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 85 75 86 / 30 10 40 40
STT 78 87 78 88 / 30 10 10 20

[cycloneye]

Good morning.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
511 AM AST FRI NOV 18 2011

.SYNOPSIS...COMBINATION OF MID TO UPPER LEVEL RIDGE TO THE WEST
THROUGH NORTH AND A TROUGH TO THE EAST THROUGH SOUTH...SHOULD
PRODUCE A GENERALLY FAIR WEATHER PATTERN FOR AT LEAST THE NEXT
COUPLE OF DAYS. AN UPPER TROUGH IS EXPECTED TO DIG ACROSS THE
LOCAL AREA LATE SUNDAY THROUGH MONDAY AND TUESDAY...RESULTING IN
A BIT MORE UNSETTLED CONDITIONS.

&&

.DISCUSSION...ALL IN ALL...EXPECT A GENERALLY FAIR WEATHER
PATTERN ACROSS THE LOCAL REGION FOR THE NEXT COUPLE OF DAYS...
WITH NO DEEP CONVECTION EXPECTED. THAT SAID...BANDS AND PATCHES
OF MOISTURE WILL MOVE ACROSS THE LOCAL AREA FROM TIME TO TIME AND
WILL COMBINE WITH LOCAL EFFECTS TO PRODUCE INTERVALS OF
CLOUDINESS AND PASSING SHOWERS WITH LOCALLY GUSTY WINDS. MOISTURE
TENDS TO INCREASE FOR SATURDAY NIGHT AND SUNDAY THROUGH EARLY NEXT
WEEK AND THIS COMBINED WITH AFOREMENTIONED DIGGING UPPER LEVEL
TROUGH SHOULD RESULT IN MORE UNSETTLED CONDITIONS DURING THIS
PERIOD.

&&

.AVIATION...VFR CONDS ARE EXPECTED AT ALL TAFS SITES THROUGH THE
FORECAST PERIOD. PASSING -SHRA WILL CONTINUE TO MOVE ACROSS THE
FORECAST AREA AND MAY PRODUCE BRIEF MVFR CIGS FROM TIME TO
TIME...PARTICULARLY ACROSS TNCM AND TIST/TISX. LLVL WINDS ARE
GENERALLY EAST...RANGING FROM 10 TO 20 KTS WITH SOME ISOLATED
GUSTS NEAR 25 KTS.

&&

.MARINE...EXPECT WINDS OF 20 KNOTS OR LESS ACROSS THE REGIONAL
WATERS THROUGH AT LEAST SUNDAY. LOCAL ATLANTIC OFF SHORE WATERS
SEAS HAVE SUBSIDED BELOW 7 FEET AND THUS THE SMALL CRAFT ADVISORY
WAS CANCELLED WITH THIS PACKAGE. HOWEVER...SMALL BOAT OPERATORS
SHOULD CONTINUE TO EXERCISE CAUTION ACROSS MOST OF THE LOCAL
COASTAL WATERS TODAY. LOW PRESSURE IS FORECAST TO DEVELOP ACROSS
THE CENTRAL ATLANTIC TONIGHT OR SATURDAY BEFORE MOVING NORTHEAST
INTO THE OPEN ATLANTIC EARLY NEXT WEEK. THIS SYSTEM IS EXPECTED
TO GENERATE LARGE SWELLS THAT COULD BEGIN IMPACTING THE LOCAL
ATLANTIC WATERS AND THE CARIBBEAN PASSAGES LATE SATURDAY NIGHT
AND SUNDAY AND THEN CONTINUE THROUGH MONDAY AND TUESDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 75 85 76 / 20 40 40 70
STT 86 75 87 77 / 20 10 20 70

[cycloneye]

This mornings discussion by Rob of Crown Weather:

http://www.crownweather.com/?page_id=4557

Rob Lightbown on November 18, 2011, 5:08 am

We are keeping an eye on an area of disturbed weather that is located about 900 miles or so east-northeast of the Leeward Islands. This disturbed weather is in association with a surface trough of low pressure which looks to be developing a surface low pressure system early this morning. Development into a sub-tropical or tropical storm is quite possible this weekend or early next week as it tracks well northeast of the Leeward Islands and well southeast of Bermuda.

The GFS model guidance continues to be the most aggressive with developing a tropical storm out in the central Atlantic this weekend while the European model remains much more muted on this development. Given the fact that we already have the combination of a large area of disturbed weather, a fairly favorable upper level pattern and run to run consistency in the models, I think there is a slightly better than 50 percent chance that we will see this disturbed weather organize into first a sub-tropical storm later this weekend and then possibly transition into a tropical storm early next week. Should this system transform into a named sub-tropical or tropical storm, its name will be Tammy.
Whatever that does develop from this disturbed weather will eventually be pulled northeastward into the eastern and northeastern Atlantic by about Wednesday of next week. It should be pointed out that anything that does develop out in the central Atlantic will not be a threat to any land masses.

[msbee]

What is all that convection to the East of us? Should we be expecting bad weather?

All of that relates to a late season tropical wave interacting with an upper trough. The same weather that we have seen in past days in the NE Caribbean will continue with patches of clouds and showers comming out from that,but the whole area will not make it to the Caribbean. What may happen from all of that is that something may try to form NE of the islands but stay out at sea.

Thanks Luis

[Macrocane]

Hi, a weak cold surge is affecting Central America today, but I've just posted the observations from last week's cold surge wich produced the coldest temperatures in Central America since April: http://www.storm2k.org/phpbb2/viewtopic.php?f=22&t=106879&p=2205751#p2205751

[cycloneye]

Barbara,this discussion that the San Juan NWS made this afternoon is one of the most detailed ones I have seen in a while from them and explains what you were asking yesterday and I replied with a brief statement of my own.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
310 PM AST FRI NOV 18 2011

.SYNOPSIS...AT UPPER LEVELS...HIGH PRESSURE PREVAILS FROM THE GULF OF
MEXICO TO THE TROPICAL ATLANTIC. A TROUGH DEEPENS JUST NORTHWEST
OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS BEGINNING SUNDAY AND
DOES NOT PULL ACROSS PUERTO RICO UNTIL THURSDAY...AFTER HAVING
WEAKENED CONSIDERABLY. A STRONGER JET AND TROUGH PASS BY NEXT
WEEKEND.

AT MID LEVELS...LOW PRESSURE NORTHEAST OF THE AREA REMAINS
NORTHEAST OF THE AREA AND STRENGTHENS CONSIDERABLY BEFORE MOVING
NORTHEAST. HIGH PRESSURE WILL BE OVER THE SOUTHEAST GULF OF MEXICO
DURING THE WEEKEND AND ONLY SIFTS INTO THE CARIBBEAN SOUTH OF THE
AREA LATE NEXT WEEK. VERY DRY AIR IS PRESENT AT MID LEVELS BRIEFLY
OVER THE WEEKEND AND THEN MORE PROMINENTLY MID WEEK NEXT WEEK.

AT LOWER LEVELS...HIGH PRESSURE LEAVES THE UNITED STATES AND MOVES
EAST ACROSS THE ATLANTIC CLOSE TO 40 NORTH. AN INVERTED TROUGH
FOUND BETWEEN 50 AND 60 WEST SPAWNS A LOW PRESSURE THAT IS
DEPICTED AS DEVELOPING STRONGLY IN THE MODELS AND MOVING NORTHEAST
BEYOND 30 NORTH 50 WEST ON TUESDAY. THIS LEAVES HIGH PRESSURE IN
THE SOUTHWEST ATLANTIC THAT WEAKENS RAPIDLY TOWARD THE END OF NEXT
WEEK. HIGH PRESSURE RETURNS TO THE WESTERN ATLANTIC NEXT WEEKEND.


&&

.DISCUSSION...TROUGHING AND THE NASCENT LOW PRESSURE NEAR 25 NORTH
55 WEST IS ALREADY VISIBLE IN THE SATELLITE IMAGERY. FORMATION OF
THIS SYSTEM WILL CAUSE SURFACE WINDS TO BACK TO THE NORTHEAST AND
AT THE SAME TIME DIRECT BANDS OF MOISTURE ROTATING AROUND THE LOW
FROM THE TROPICS TOWARD THE LOCAL AREA DURING THE NEXT 5 DAYS. AS
THE LOW RETREATS TO THE NORTHEAST MOISTURE SHOULD WEAKEN. THIS
WILL CONTINUE A PATTERN THAT IS BECOMING FAMILIAR TO THOSE IN
PUERTO RICO AND THE U.S.VIRGIN ISLANDS: NIGHT AND EARLY MORNING
SHOWERS ON THE NORTHEAST COAST...SOMETIMES NUMEROUS...AND AFTERNOON
SHOWERS AND OCCASIONAL THUNDERSTORMS DEVELOPING IN SOUTHWEST
PUERTO RICO. ALL THIS...WITH SCATTERED NIGHT AND ISOLATED DAYTIME
SHOWERS AROUND THE U.S. VIRGIN ISLANDS.

IN THE NEAR TERM A BAND OF DRIER AIR IS PASSING THROUGH THE AREA
AT PRESENT AND WILL BE FOLLOWED BY ANOTHER AREA OF BETTER MOISTURE
AND INSTABILITY. MID LEVELS ARE GENERALLY DRY BUT BECOME VERY DRY
MID WEEK FROM SUBSIDENCE AROUND THE HIGH JUST NORTHWEST OF PUERTO
RICO NEXT WEEK AND THIS WILL CONTRIBUTE TO A GENERAL DRYING TREND
BEGINNING THEN...AND NOT ENDING BEFORE NEXT WEEKEND.

AS A SIDE NOTE...THE GFS AND ECMWF BOTH SHOW A WEAK LOBE OF LOW
PRESSURE SEPARATING FROM THE CUT-OFF IN THE ATLANTIC AND MOVING SOUTH
SOUTHWEST OVER THE LEEWARD ISLANDS EARLY SUNDAY...BRINGING AN
ADDITIONAL SHOT OF MOISTURE AND SHOWERS TO PUERTO RICO AND THE
U.S. VIRGIN ISLANDS.

&&

.AVIATION...VFR CONDS WILL CONT TONIGHT XCPT IN SCT SHRA NR
TJSJ/TJBQ/TIST/TISX/TNCM/TKPK. BUT CIGS/VSBY WILL BE VERY BRIEFLY
MVFR FOR THE FEW TAFS THAT GET IT. WINDS BLO FL200 WILL BE NE
15-25 KTS THROUGH SAT.

&&

.MARINE...SEAS ARE EXPECTED TO RISE TO SMALL CRAFT CRITERION
SATURDAY NIGHT AS SWELL FROM THE LOW PRESSURE FORMING IN THE
ATLANTIC BEGIN ARRIVING. AT THIS TIME...CONSIDERING THE STRENGTHENING
THAT THE GFS GIVES THE LOW...SEAS MAY REACH 10 TO 11 FEET IN THE
OUTER WATERS BY EARLY NEXT WEEK. SEAS DO NOT FALL BELOW SMALL
CRAFT ADVISORY CRITERIA UNTIL THANKSGIVING DAY...IF THEN.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 84 75 84 / 30 10 50 60
STT 75 86 76 86 / 50 10 40 50

[msbee]

Thanks Luis
Great discussion. Good information.

[Gustywind]

[cycloneye]

An updated discussion made tonight.


AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
906 PM AST FRI NOV 18 2011

.SYNOPSIS...A SFC TROUGH EAST OF THE AREA COULD DEVELOP INTO A
SUBTROPICAL OR TROPICAL CYCLONE OVR THE NEXT FEW DAYS. AT UPPER
LEVELS...TUTT TO THE EAST WILL LIFT OUT WITH A BROAD TROUGH
ESTABLISHING ACROSS THE WRN ATLC NEXT WEEK.

&&

.DISCUSSION...DENSE FOG HAS BEEN OBSERVED ON 11-3.9 MICRON IMAGERY
THIS EVENING ACROSS CIALES...OROCOVIS...COROZAL AND CAYEY. 18Z
PARALLEL RUN OF THE PR3KM NAM SHOWS DENSE FOG AFFECTING THE AREA
FROM CIALES EAST TO CAYEY ALL NIGHT. WILL HANDLE DENSE FOG WITH
NOW`S OR SPS`S.

SHALLOW MOISTURE AND INSTABILITY ARE EXPECTED TO WANE AFTER 06Z
TONIGHT PER BLENDED TPW IMAGERY AND MODEL VERTICAL PLOTS OF
THETAE. SO XPC SHOWERS TO DECREASE IN CVRG/INTENSITY OVERNIGHT OR
PERHAPS COMPLETELY DISSIPATE. MODELS SHOW A MIN IN PWAT TOMORROW
AFTERNOON WITH VALUES JUST UNDER AN INCH. WHILE AM NOT EXPECTING
MORE THAN A FEW SPRINKLES OR VERY BRIEF -SHRA NOT CONFIDENT ENOUGH
TO REMOVE POPS COMPLETELY AS GFS SHOWS LAYER RH VALUES INCREASING
THROUGH THE DAY.

MOISTURE AND INSTABILITY INCREASE AGAIN TOWARD 12Z SUN AS S/W
ENERGY BEGINS TO DIG ACROSS THE AREA. XPC NMRS SHOWERS TO BREAK
OUT SUN MORNING. UNSETTLED WX WILL PERSIST THRU MON WITH
CONDITIONS IMPROVING BY TUE AS TROF AXIS SHIFTS EAST OF THE AREA.
FAIR WX WILL THEN PERSIST THROUGH MIDDLE OF NEXT WEEK.

&&

.AVIATION...VFR THROUGH 00Z SUN WITH INCREASING PROBS OF MVFR CIGS
AT JSJ/JBQ IN GUSTY NE WINDS AND SHRA. CONDITIONS IMPROVE AGAIN ON TUE.

&&

.MARINE...SEAS XPCD TO INCREASE LATE TOMORROW ACROSS AMZ710 AND
CONTINUE TO DETERIORATE AS PRES GRADIENT TIGHTENS BETWEEN HIGH
PRES TO THE NORTH AND DEVELOPING LOW TO THE NORTHEAST. SHORTER
PERIOD SEAS WILL BECOME INCREASINGLY DOMINATED BY LONGER PERIOD
SEAS OR SWELLS GENERATED FROM LOW PRES TO THE NORTHEAST. SMALL
CRAFT AND HIGH SURF ADVISORIES APPEAR LIKELY EARLY NEXT WEEK.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 85 75 85 / 30 20 50 60
STT 78 86 78 86 / 20 10 40 50

[cycloneye]

Good morning. Passing showers will be the rule for the next few days and watch out in the beaches for high swells.


AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
622 AM AST SAT NOV 19 2011

.SYNOPSIS...THE COMBINATION OF A MID TO UPPER LEVEL RIDGE TO THE
WEST THROUGH NORTH AND A TROUGH TO THE EAST THROUGH SOUTH...SHOULD
RESULT IN A GENERALLY FAIR WEATHER PATTERN FOR AT LEAST THE NEXT
COUPLE OF DAYS. AN UPPER TROUGH IS EXPECTED TO GRADUALLY SHARPEN
UP TO THE NORTH AND THEN ACROSS THE LOCAL AREA LATE SUNDAY THROUGH
MONDAY AND TUESDAY...RESULTING IN A BIT MORE UNSETTLED CONDITIONS.

&&

.DISCUSSION...ALL IN ALL...STILL EXPECT A GENERALLY FAIR WEATHER
PATTERN ACROSS THE LOCAL REGION FOR THE NEXT COUPLE OF DAYS...
WITH NO PERSISTENT DEEP CONVECTION EXPECTED. THAT SAID...BANDS
AND PATCHES OF MOISTURE WILL MOVE ACROSS THE LOCAL AREA FROM TIME
TO TIME AND WILL BECOME MORE FREQUENT BEGINNING LATER THIS
AFTERNOON AND TONIGHT AND THEN CONTINUING THROUGH EARLY NEXT
WEEK. THIS MOISTURE WILL COMBINE WITH LOCAL EFFECTS AND EVENTUALLY
THE AFOREMENTIONED SHARPENING UPPER LEVEL TROUGH...TO PRODUCE
INTERVALS OF CLOUDINESS AND SHOWERS WITH LOCALLY GUSTY WINDS.

&&

.AVIATION...VFR CONDS ARE EXPECTED AT ALL TAF SITES THROUGH THE
FORECAST PERIOD. HOWEVER...PASSING -SHRA WILL CONTINUE TO MOVE
ACROSS THE AREA TODAY AND MAY PRODUCE BRIEF MVFR CIGS OVER THE
WINDWARD SITES. LLVL WINDS WILL REMAIN FROM THE NORTHEAST AT 10
TO 20 KTS WITH SOME ISOLATED GUSTS NEAR 25 KTS.

&&

.MARINE...EXPECT WINDS OF 21 KNOTS OR LESS ACROSS THE REGIONAL
WATERS THROUGH AT LEAST MONDAY. SMALL BOAT OPERATORS SHOULD
CONTINUE TO EXERCISE CAUTION ACROSS MOST OF THE LOCAL COASTAL
WATERS TODAY. SURFACE LOW PRESSURE IS FORECAST TO CONTINUE TO
DEVELOP ACROSS THE CENTRAL ATLANTIC TODAY AND TONIGHT BEFORE
MOVING NORTHEAST INTO THE OPEN ATLANTIC EARLY NEXT WEEK. THIS
SYSTEM IS EXPECTED TO GENERATE LARGE NORTHEAST SWELLS THAT WILL
PROBABLY BEGIN TO AFFECT THE LOCAL ATLANTIC WATERS AND THE
CARIBBEAN PASSAGES AS EARLY AS LATE TONIGHT BUT ESPECIALLY ON
SUNDAY...AND THEN CONTINUE THROUGH MONDAY AND TUESDAY AND
PROBABLY WEDNESDAY. A SMALL CRAFT ADVISORY WILL GO INTO EFFECT
FOR THE LOCAL ATLANTIC OFF SHORE WATERS (AMZ710) AT 9 PM AST THIS
EVENING AND THEN EXPAND TO OTHER WATERS THEREAFTER. IN ADDITION...
A HIGH SURF ADVISORY WILL LIKELY BE NEEDED FOR NORTHERN EXPOSED
COASTLINES OF MOST OF THE LOCAL ISLANDS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 86 76 85 76 / 20 50 60 60
STT 87 77 87 77 / 20 40 50 60

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1101 AM AST SAT NOV 19 2011

.UPDATE...SATELLITE VISUAL AND PRECIPITABLE WATER IMAGES CLEARLY
SHOW THE MESOSCALE SHORTWAVE AND SMALL AREA OF HIGHER MOISTURE
DIRECTLY NORTH OF PR AND CENTERED NEAR 20N. RADAR SHOWS LIMITED
CONVECTION WITH THIS BUT MOST IS PROBABLY TOO SHALLOW AND OUT OF
ITS RANGE. 12Z NAM INITIALIZED IT POORLY AND EARLIER MODELS
DIDN/T DO ANY BETTER...SO WILL RELY ON EXTRAPOLATION FOR A MODEL.
PRECIPITABLE WATER FROM SATELLITE INDICATES ABOUT 1.7 INCHES
THOUGH 12KM NAM RAISES IT TO 2.0 OVER WESTERN PR...SEEMS UNLIKELY
ATTM. OVER A BROADER SCALE MODELS SUGGEST WE WOULD BE UNDER A
GENERAL AREA OF CONVERGENT UPPER LEVEL FLOW THOUGH NOT SURE THAT
IS TO BE TRUSTED GIVEN THE POOR INITIALIZATION.

BELIEVE MOST OF THE CONVECTION ASSOCIATED WITH THE WAVE WILL MISS
PR THIS AFTERNOON BUT IT APPEARS THAT SCATTERED CONVECTION AND
ISOLATED THUNDER IN THE SOUTHWEST IS A PRUDENT INCLUSION AND DID
SO FOR THE MORNING UPDATE. ELSEWHERE INCLUDING USVI WE REMAIN IN
GENERALLY DRY NORTHEAST FLOW AND RESULTANT ISOLATED SHOWERS...NO
MORE THAN YESTERDAY...WOULD RESULT AGAIN THIS AFTERNOON.

&&

.AVIATION...GENERALLY VFR CONDS TO CONT ALL TAF SITES. TJMZ/TJBZ TO
HAVE HIGHEST CHANCE OF SHRA THIS AFTERNOON AND MAYBE VCNTY TSRA AT
TJMZ. OTHERWISE MVFR CIGS IS A REMOTE POSSIBILITY FOR THE FEW SHRA
THAT WILL OCCUR...MAINLY TONITE AT WINDWARD SITES. WINDS SFC TO
FL200 WILL BE NE 15 TO 25 KTS THRU SUNDAY.

[cycloneye]

AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
304 PM AST SAT NOV 19 2011

.SYNOPSIS...AT UPPER LEVELS...A NORTHEAST-SOUTHWEST TROUGH DEVELOPS
OVER HISPANIOLA ON MONDAY AND MOVES OVER PUERTO RICO AND THE U.S.
VIRGIN ISLANDS ON WEDNESDAY. AFTER A PERIOD OF NEARLY ZONAL FLOW A
SECOND TROUGH FOLLOWS ON THE FOLLOWING SUNDAY.

AT MID LEVELS...HIGH PRESSURE FROM THE GULF OF MEXICO TO THE
BAHAMAS PULLS BACK TO THE WESTERN GULF OF MEXICO AS A LONG WAVE
TROUGH MOVES TOWARD THE LOCAL AREA DURING THE WEEK AHEAD. LOW
PRESSURE TO THE EAST NORTHEAST DEVELOPS SUNDAY THROUGH WEDNESDAY
BUT MOVES NORTH AND THEN NORTHEAST AWAY FROM THE AREA.

AT LOWER LEVELS...LOW PRESSURE EAST OF THE AREA BETWEEN 50 AND 60
WEST MOVES NORTH AND DEVELOPS SUNDAY THROUGH WEDNESDAY. WHILE HIGH
PRESSURE CONTINUES NORTHWEST OF THE AREA. ALTHOUGH A PASSING LOW
PRESSURE CENTER WELL TO THE NORTH BRIEFLY WEAKENS THIS RIDGE ON
THURSDAY...HIGH PRESSURE RE-BUILDS INTO THE WESTERN ATLANTIC FRIDAY
AND SATURDAY OF NEXT WEEK. THE RESULT IS THAT NORTHEAST TO EAST
NORTHEAST FLOW PREVAILS THROUGH THE ENTIRE 10-DAY PERIOD WITH
PATCHES OF LOW LEVEL MOISTURE MOVING ACROSS THE LOCAL ISLANDS.

&&

.DISCUSSION...SKIES WERE MOSTLY CLEAR THIS AFTERNOON AND SHOWERS
CLEARED OFF OF THE LAND AREAS BEFORE NOON. AS OF 3 PM AST SHOWERS
HAD NOT BEEN ABLE TO DEVELOP OVER SOUTHWEST PUERTO RICO. A BAND OF
BETTER MOISTURE IS ARRIVING ON THE NORTHEAST COAST OF PUERTO RICO
AND THE NORTHERN VIRGIN ISLANDS...AND SHOWERS SHOULD INCREASE
OVERNIGHT. MODLES HAVE CHANGED THEIR SOLUTION SUBSTANTIVELY WITH
NOT AS MUCH UPPER LEVEL TROUGHING TO THE EAST AND WEAKER LOW
PRESSURE MIGRATING SOUTH. CURRENTLY MODELS INDICATE THAT BETTER
MOISTURE WILL ONLY ARRIVE DURING THE DAY TOMORROW AND THIS SHOULD
CAUSE SHOWERS TO SPREAD OVER THE AREA DURING THE DAY WITH THE MOST
SHOWER ACTIVITY OVER NORTHEAST PUERTO RICO DUE TO OROGRAPHIC
EFFECTS. MODELS SHOWED A LOW PRESSURE LOBE OF THE MAIN LOW MOVING
SOUTH OVER THE LEEWARD ISLANDS BUT IN THE 19/12Z RUN THE GFS AND
THE ECMWF SHOWED ONLY A TROUGH MOVING THROUGH ON SUNDAY WITH AN
INCREASE IN THE WINDS AT 850 MB TO AS MUCH AS 30 TO 35 KT...THIS
MAY BE TOO HIGH. HOWEVER THE MOISTURE SHOULD STILL BE ENOUGH TO
BRING NUMEROUS SHOWER DURING THE DAY SUNDAY. MODELS SUGGEST THAT
THIS MOISTURE ALTHOUGH NOT PARTICULARLY DEEP SHOULD ALSO BE ABLE
TO FUEL SHOWERS THROUGH MONDAY. NORTHEAST FLOW TAPERS OFF AS THE
LOW PRESSURE IN THE CENTRAL ATLANTIC MOVES NORTH AND THEN
NORTHEAST AND WINDS WILL ABATE...BUT SOME PASSING SHOWERS ARE
NEVERTHELESS EXPECTED TO CONTINUE IN THE SAME GENERAL PATTERN OF
NORTHEAST COASTAL SHOWERS NIGHT AND EARLY MORNING FOLLOWED BY
SOUTHWEST CONVECTION...GENERALLY ISOLATED...IN THE AFTERNOONS
THROUGH THE THANKSGIVING WEEKEND.

&&

.AVIATION...VFR CONDS CONT AT TAF SITES. STRAY SHRA STILL PSBL THIS
AFTERNOON FOR TJMZ BUT WILL BE LATE IF IT DOES DEVELOP. OTHERWISE
MVFR CIGS BCMG PSBL AGAIN LATE TONIGHT AT WINDWARD SITES AS SHRA INCR
IN NE FLOW. WINDS SFC TO FL200 WILL BE NE 15 TO 25 KTS THRU
SUNDAY.

&&

.MARINE...AS LOW PRESSURE DEVELOPS IN THE CENTRAL ATLANTIC AND
HIGH PRESSURE CONTINUES NORTHWEST OF THE AREA INCREASING SWELL
WILL DEVELOP AND SPREAD THROUGH THE LOCAL WATERS FROM THE
NORTHEAST. SMALL CRAFT ADVISORIES GO UP TONIGHT AND SPREAD INTO
THE PASSAGES ON SUNDAY NIGHT. SEAS IN THE OUTER ATLANTIC WATERS
REMAIN AS HIGH AS 7 FEET FOR THE REST OF THE WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 75 85 75 84 / 40 60 50 50
STT 76 86 76 85 / 50 60 40 50

[Macrocane]

Hi, I want to share this picture with you, I took it a few minutes ago and it's a nicely developed cumulonimbus

[cycloneye]

Impressive cloud formation Macrocane.

The next three days will be with plenty of showers moving thru the NE Caribbean with rough seas,so let's watch how all of this unfolds.


AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
954 PM AST SAT NOV 19 2011

.SYNOPSIS...LONG FETCH NORTHEAST FLOW WILL BRING BREEZY AND
SHOWERY WEATHER ACROSS THE AREA SUN-TUE WITH CONDITIONS IMPROVING
MID WEEK. LARGE SWELLS WILL IMPACT THE ATLC COASTAL WATERS AND
PASSAGES EARLY IN THE WEEK WITH ROUGH SEAS AND DANGEROUS SURF
CONDITIONS.

&&

.DISCUSSION...LATEST WATER VAPOR IMAGERY SHOWS S/W ENERGY
BEGINNING TO DIG NORTH OF THE REGION WHILE AT THE SFC PRES
GRADIENT IS BEGINNING TO TIGHTEN IN RESPONSE TO DEVELOPING LOW
ACROSS THE CNTRL ATLC AND STRONG HIGH PRES TO THE NORTH. 00Z JSJ
RAOB SHOWS THAT NE FLOW HAS DEEPENED WITH 20-25 KT WINDS BETWEEN
5-15 KFT. THIS HAS RESULTED IN AN INCREASE IN SHOWER ACTIVITY THIS
EVENING AND A THICK STRATUS LAYER ACROSS THE CENTRAL CORDILLERA.
OVERNIGHT...MODELS SHOW INCREASING MOISTURE AND SHALLOW INSTABILITY
WITH SHOWERS BECOMING HEAVIER AND MORE NMRS TOWARD 12Z WITH GUSTY
WINDS AND BKN CIGS IN MDT SHRA. SHOWERS WILL BE HEAVIEST ACROSS
NE PR AND ESPECIALLY EL YUNQUE AREA IN FVRBL UPSLOPE FLOW WITH
SOME MINOR FLOODING POSSIBLE THERE. TEMPS ACROSS THE HIGHER ELEVS
ABV 2500 FT ARE NOT LIKELY TO GET OUT OF THE MID 60S IN THICK
CLOUDS AND PERSISTENT SHRA OR +DZ. CONDITIONS WILL REMAIN CLOUDY
AND SHOWERY THROUGH MON WITH SOME SLIGHT IMPROVEMENT ON TUE BUT
STILL WITH A LOT OF CLOUDS.

WEATHER IMPROVES MID WEEK AS TROF AXIS SHIFTS EAST OF THE AREA AND
MID LEVEL RIDGING BEGINS TO BUILD FROM THE WEST.

&&

.AVIATION...VFR CONDITIONS LIKELY THROUGH 12Z SUN BUT CONDITIONS
WILL BEGIN TO DETERIORATE AFTER THAT AT JSJ/IST WITH MORE FREQ
PERIODS OF MVFR CIGS IN SHRA. CAN`T RULED OUT A TSRA EITHER LATE
IN THE AFTERNOON. PROBS FOR PREDOMINANT MVFR CIGS AT JSJ AND IST
WILL REMAIN RATHER HIGH THRU TUE WITH IMPROVEMENT NOT LIKELY
UNTIL TUE. WINDS AT TIST COULD BE RATHER GUSTY NEXT 24 HRS DUE
STRONG NE FLOW ACCELERATING DOWN FROM CROWN MOUNTAIN DUE TO
GRAVITY IN FVBRL NE FLOW. GUSTS 30-35 KT POSSIBLE.

&&

.MARINE...SEAS AT BUOY 41043 ARE BEGINNING TO INCREASE THIS
EVENING WITH 7 FT SEAS IN MAINLY NE WIND WAVES. SEAS WILL
DETERIORATE RAPIDLY AFTER 12Z WITH NE SWELLS PEAKING SUN NIGHT.
ROUGH SEAS AND DANGEROUS SURF CONDITIONS WILL PERSIST THROUGH TUE.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 78 85 78 84 / 70 70 70 50
STT 78 86 78 85 / 70 70 50 50

[cycloneye]

Good morning.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
620 AM AST SUN NOV 20 2011

.SYNOPSIS...THE COMBINATION OF A MID TO UPPER LEVEL RIDGE TO THE
WEST THROUGH NORTH AND A TROUGH TO THE EAST THROUGH SOUTH...WILL
CONTINUE TO PRODUCE A RATHER DEEP LAYERED...MOIST...LONG FETCH
NORTHEAST FLOW F0R TODAY THROUGH MONDAY AND TUESDAY. A GENERALLY
FAIR WEATHER PATTERN WILL THEN RESUME FOR WEDNESDAY AND THURSDAY
AND POSSIBLY FRIDAY TOO...AS MID TO UPPER LEVEL HIGH PRESSURE
TAKES CONTROL OF THE LOCAL WEATHER AGAIN.

&&

.DISCUSSION...A LOW LEVEL DISTURBANCE AND ASSOCIATED MOISTURE WILL
CONTINUE TO APPROACH AND THEN MOVE SOUTHWEST ACROSS THE LOCAL
ISLANDS TODAY THROUGH TONIGHT...MAKING FOR INCREASINGLY UNSETTLED
CONDITIONS WITH VARIABLY CLOUDY SKIES AND SCATTERED TO NUMEROUS
SHOWERS WITH GUSTY WINDS. ADDITIONAL BANDS AND PATCHES OF
MOISTURE WILL MOVE ACROSS THE LOCAL AREA FROM TIME TO TIME FOR
MONDAY THROUGH TUESDAY AND WILL COMBINE WITH LOCAL EFFECTS AND
APPROACHING UPPER LEVEL SHORT WAVE...TO PRODUCE MORE INTERVALS OF
CLOUDINESS AND SHOWERS WITH GUSTY WINDS. FOR WEDNESDAY AND
THURSDAY AND POSSIBLY FRIDAY ALSO...EXPECT AN "OVERALL" GENERALLY
FAIR AND DRIER WEATHER PATTERN...AS AFOREMENTIONED MID TO UPPER
LEVEL RIDGE TAKES CONTROL OF THE LOCAL WEATHER REGIME AGAIN.

&&

.AVIATION...LONG FETCH NORTHEAST TRADE WIND FLOW WILL CONTINUE TO
BRING PATCHES OF MOISTURE TO THE LOCAL REGION. PASSING SHWRS
EMBEDDED IN THE TRADES COULD PRODUCE BRIEF MVFR CONDS ACROSS TJSJ
AND TIST/TNCM...ESPECIALLY BTWN 14-19Z. CIGS WILL BE MAINLY
025-050 WITHIN PASSING SHRA...WITH SOME GROUPS OF BKN020. WINDS
SFC TO FL200 WILL BE MAINLY NE AT 15 TO 30 KTS THRU THE FORECAST
PERIOD.

&&

.MARINE...THE PRESSURE GRADIENT WILL CONTINUE TO TIGHTEN IN
RESPONSE TO DEEPENING LOW PRESSURE ACROSS THE CENTRAL ATLANTIC
AND HIGH PRESSURE WELL TO THE NORTH...RESULTING IN MODERATE TO
FRESH...AND LOCALLY STRONG WINDS ACROSS THE REGIONAL WATERS
THROUGH TUESDAY. A LONG FETCH NORTHEAST FLOW WILL CONTINUE TO
GENERATE LARGE SWELLS THAT WILL BEGIN TO AFFECT THE ATLANTIC
COASTAL WATERS AND THE CARIBBEAN PASSAGES TODAY AND THEN CONTINUE
THROUGH WEDNESDAY. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR
THE LOCAL ATLANTIC OFF SHORE WATERS AND THE ANEGADA PASSAGE AND
WILL GO INTO EFFECT FOR MOST OF THE REMAINING LOCAL COASTAL
WATERS AT NOON AST TODAY. BASED ON THE LATEST BUOY AND MODEL
DATA...WE OPTED TO NOT ISSUE A HIGH SURF ADVISORY FOR THE
NORTHERN EXPOSED COASTLINES OF THE LOCAL ISLANDS WITH THIS
PACKAGE...AS FOR THE SHORT TERM IT WOULD APPEAR TO BE A NON-
EXISTENT OR VERY BORDERLINE 10 FOOT BREAKING WAVE EVENT.
HOWEVER...THIS WILL PROBABLY CHANGE FOR LATE THIS AFTERNOON AND
TONIGHT AND THESE ADVISORIES MAY STILL BE NEEDED LATER.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 85 76 85 75 / 70 70 50 40
STT 86 76 86 76 / 60 50 50 50

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
256 PM AST SUN NOV 20 2011

.SYNOPSIS...AT UPPER LEVELS...A TROUGH IS MOVING THROUGH PUERTO
RICO FROM THE WEST. ANOTHER TROUGH WILL DEVELOP OVER EASTERN CUBA
TOMORROW AND MOVE THROUGH PUERTO RICO ON WEDNESDAY AND THE U.S.
VIRGIN ISLANDS ON WEDNESDAY NIGHT. A LONG WAVE TROUGH OVER FLORIDA
ON THURSDAY NIGHT WILL SHARPEN AS A LOW CUTS OFF IN THE ATLANTIC
ABOUT 700 MILES NORTH OF PUERTO RICO AND A JET FORMS ON SOUTHEAST
SIDE. IT WILL PASS NEXT WEEKEND.

AT MID LEVELS...LOW PRESSURE BETWEEN 50 AND 60 WEST WILL MOVE
NORTH AND DEEPEN NOW THROUGH TUESDAY...THE LOW THEN MOVES EAST AND
STALLS BETWEEN 40 AND 50 WEST ON THURSDAY. A TROUGH FROM THIS LOW
WILL HANG BACK OVER THE CARIBBEAN THROUGH MUCH OF THE WEEK. ON
THURSDAY A STRONG TROUGH LEAVES FLORIDA TOWARD THE SOUTHEAST. A
LOW CUTS OFF ON FRIDAY NIGHT AND REMAINS NORTH OF PUERTO RICO
THROUGH THE FOLLOWING WEEKEND.

AT LOWER LEVELS...A RIDGE OF HIGH PRESSURE STRETCHES FROM SOUTH
CAROLINA TO THE CENTRAL ATLANTIC NEAR 40 DEGREES NORTH. LOW
PRESSURE EAST NORTHEAST OF THE LOCAL AREA NEAR 54 WEST WILL
INTENSIFY AS IT MOVES NORTH NORTHEAST. ON TUESDAY IT WILL BEGIN
MOVING EASTERLY. AFTER ABOUT MID WEEK PUERTO RICO AND THE U.S.
VIRGIN ISLANDS WILL ONLY BE UNDER THE INFLUENCE OF THE NORTH-SOUTH
GRADIENT BETWEEN LOW PRESSURE IN THE SOUTHERN CARIBBEAN AND HIGH
PRESSURE ALONG AND JUST NORTH OF 40 NORTH.


&&

.DISCUSSION...WIDELY SPACED SHOWERS CONTINUE TO MARCH ONTO THE
COAST OF PUERTO RICO WITH MODERATE TO HEAVY RAINFALL LASTING ON
THE ORDER OF MINUTES...YIELDING AMOUNTS OF LESS THAN ONE TENTH
INCH. THIS PATTERN IS EXPECTED TO CONTINUE AS A WEAK LOBE OF LOW
PRESSURE SEPARATED FROM THE LOW IN THE CENTRAL ATLANTIC CONTINUES
TO MIGRATE SOUTH NEAR THE LEEWARD ISLANDS TONIGHT. SHOWERS WILL
SLOWLY DIMINISH AFTER TONIGHT FOR THE NEXT SEVERAL DAYS WHILE
CONTINUING TO AFFECT THE ENTIRE NORTHERN COAST AND EASTERN THIRD
OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS. AS THE LOW PRESSURE AT
THE SURFACE LIFTS NORTH AND THEN EAST...GRADIENTS WILL
SLACKEN...LIKELY BEGINNING MONDAY NIGHT...AND WINDS WILL ALSO
DIMINISH. A GENERAL DRYING TREND ALSO BEGINS AS LESS MOISTURE
MIGRATES OVER THE AREA FROM THE LOW...BUT ISOLATED TO SCATTERED
SHOWERS WILL STILL CONTINUE MOST OF THE REST OF THE WEEK OVER
THE WINDWARD COASTS AND SLOPES OF PUERTO RICO AND OVER THE U.S.
VIRGIN ISLANDS. AREAS OF MOISTURE ARE ALSO EXPECTED WHEN THE LONG
WAVE TROUGH APPROACHES THE AREA NEXT WEEKEND. THROUGH THIS
ALL...WINDS REMAIN MOSTLY NORTHEAST EXCEPT FOR A PERIOD OF WINDS
FROM THE EAST WEDNESDAY NIGHT THROUGH SATURDAY.

&&

.AVIATION...NORTHEAST TRADE WIND FLOW WILL CONTINUE TO BRING QUICK
PASSING SHOWERS ACROSS THE LOCAL ISLANDS. THESE SHOWERS COULD
PRODUCE BRIEF MVFR CONDS ACROSS TJSJ...TIST...TISX...TNCM...AND
TKPK. SKIES WILL BE MAINLY SCT025-050 WITH PASSING SHRA...AND POSSIBLE BRIEF
BKN020 OR LESS...ESPECIALLY AT TKPK AND TNCM. WINDS SFC TO FL200
WILL BE MAINLY NE AT 15 TO 25 KTS THRU THE FORECAST PERIOD.
HOWEVER...TNCM AND TKPK MAY OBSERVE LIGHTER AND MORE VARIABLE
WINDS.

&&

.MARINE...SEAS WILL PEAK TONIGHT OR EARLY MONDAY...BUT SMALL CRAFT
ADVISORIES ARE LIKELY TO CONTINUE IN THE OUTER ATLANTIC WATERS
THROUGH WEDNESDAY. SEAS SHOULD CONTINUE TO IMPROVE UNTIL SATURDAY.
WINDS WILL ALSO BEGIN TO DIMINISH AFTER MONDAY.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 85 75 85 / 80 70 60 40
STT 76 86 76 86 / 50 50 50 40

[cycloneye]

This is a note about the Soufriere Volcano that has tried to throw some ash and steam for the past two weeks and today, advisories were issued by the Washington agency that has to do with those. See the latest at the Soufriere Volcano thread on the Geology forum.

viewtopic.php?f=67&t=107244&p=2205895#p2205895