Caribbean - Central America Weather

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
256 PM AST SAT SEP 4 2010

.SYNOPSIS...AN UPPER LEVEL LOW ACROSS THE NORTHEASTERN CARIBBEAN
THIS AFTERNOON WILL TRACK WESTWARD AND AWAY FROM THE LOCAL ISLANDS
THROUGH EARLY NEXT WEEK. THE REMNANTS OF FORMER TROPICAL STORM
GASTON ARE EXPECTED TO REDEVELOP INTO A TROPICAL CYCLONE EITHER
LATER TONIGHT OR SUNDAY...AND MAY IMPACT THE LOCAL ISLANDS DURING
THE MIDDLE OF THE UPCOMING WEEK.

&&

.DISCUSSION...AN AREA OF LOW LEVEL MOISTURE MOVE FROM THE NE
ACROSS THE ATLANTIC WATERS...GENERATING ISOLATED TO SCATTERED
SHOWERS ACROSS THE EASTERN PORTIONS OF PUERTO RICO AND THE EASTERN
ADJACENT ISLANDS. THESE SHOWERS ARE EXPECTED TO LINGER THROUGH THE
EVENING HOURS.

LATEST SATELLITE IMAGERY AND MIMIC-TPW FROM SHOWED THAT THE
PREVAILING DRIER AIR MASS WILL CONTINUE ACROSS THE NORTH EASTERN
CARIBBEAN DURING THE NEXT FEW DAYS. CLOUDINESS...SHOWERS AND
THUNDERSTORMS WILL INCREASE ACROSS THE FA LATE DURING THE UPCOMING
WEEK AS THE REMNANTS OF TROPICAL STORMS GASTON APPROACH TO THE
REGION. THIS SYSTEM HAS THE POTENTIAL FOR RE-DEVELOPMENT INTO A
TROPICAL CYCLONE BEFORE ENTERING THE CARIBBEAN. WHILE THE EXACT
TIMING...TRACK AND INTENSITY ALL REMAIN UNCERTAIN AT THIS
TIME...LOCAL RESIDENTS AND TOURISTS ARE ENCOURAGED TO PAY CLOSE
ATTENTION TO THIS SYSTEM DURING THIS HOLIDAY WEEKEND...AS IT HAS
THE POTENTIAL TO IMPACT THE LOCAL ISLANDS BY THE MIDDLE OF NEXT
WEEK. NOT CHANGES WERE DONE TO THE PREVIOUS FORECAST PACKAGE.


&&

.AVIATION...PREVAILING VFR CONDITIONS ARE EXPECTED ACROSS ALL TAF
SITES THROUGH 05/14Z...ALTHOUGH A VCSH OR -SHRA WILL BE POSSIBLE
ACROSS THE VI...TKPK AND TNCM. AFT 05/16Z...EXPECT SHRA AND TSRA
DEVELOPMENT ACROSS THE CORDILLERA CENTRAL...RESULTING IN LOCAL
MOUNTAIN OBSCURATIONS AS WELL AS BRIEF MVFR CIGS AND VSBYS ACROSS
TJMZ AND TJBQ BETWEEN 05/17Z-05/21Z. LLVL WINDS FLOW WILL CONTINUE
FROM THE EAST NORTHEAST DURING THE NEXT 24 HOURS.

&&

.MARINE...SEAS WILL CONTINUE TO SUBSIDE THROUGH TONIGHT...TRANQUIL
CONDITIONS WILL PREVAIL THROUGH AT LEAST MONDAY. AFTER MONDAY
MARINE CONDITIONS WILL DEPEND ON THE ACTUAL TRACK AND
INTENSITY FORECAST OF GASTON.

[cycloneye]

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
1016 PM AST SAT SEP 4 2010

.UPDATE...UPPER LAYERS HAVE MOISTENED CONSIDERABLY SINCE 12Z AS
INDICATED BY 05/00Z SOUNDING. NEXRAD RADAR SHOWS SOME THUNDERSTORMS
IN THE ATLANTIC NORTH OF RIO GRANDE AND CULEBRA MOVING SOUTHWEST.
CULEBRA WILL LIKELY BE WET BEFORE 10 PM AST. THESE SHOWERS HAVE A
GOOD CHANCE OF GETTING TO THE NORTHEAST COAST OF PUERTO RICO AS
WELL.


&&

.DISCUSSION...THERE IS AN INVERTED TROUGH OVER THE WINDWARD
ISLANDS WHICH IS PRODUCING SOME CONVECTION AND IS LIKELY A
REFLECTION OF THE UPPER LOW MOVING OVER PUERTO RICO AT THIS TIME. THE
UPPER LOW WILL BRING CONSIDERABLE DIVERGENCE ALOFT SUNDAY NIGHT
FROM SPEED DIVERGENCE IN THE JET OF 45 TO 55 KNOT WINDS THAT
DEVELOP AND MAY HELP ENHANCE WHATEVER CONVECTION THAT CAN GROW IN
THE TROUGH WHEN IT ALSO PASSES ON SUNDAY NIGHT. MID LEVEL
MOISTURE IS NOT PARTICULARLY GOOD OVER US AT THAT TIME SO EXPECT
ONLY SCATTERED SHOWERS AND THUNDERSTORMS THEN.

THE CONVECTION IN THE REMNANT LOW OF GASTON HAS WEAKENED FURTHER
IN THE LAST SEVERAL HOURS AND THE GFS 18Z RUN NOW KEEPS IT AS AN
OPEN WAVE WHICH PASSES TO THE SOUTH...YES SOUTH...OF PUERTO RICO
AND SAINT CROIX. THIS...HOWEVER...BRINGS THE BEST WINDS OF THE
WAVE DIRECTLY OVER THE U.S. VIRGIN ISLANDS. HAVE RAISED THE
COASTAL WATERS FORECAST WINDS IN TO THE 20 TO 26 KNOT RANGE IN A
NUMBER OF ZONES...BUT THE INTENSITY AND TIMING OF THE WINDS WILL
ONLY HOLD IF GASTON DOES NOT RE-DEVELOP. RE-DEVELOPMENT STILL
SEEMS HIGHLY LIKELY. SEVERAL THINGS POINT TO ITS FAVOR. ONE...THE
PRECIPITABLE WATER ANIMATION...KNOWN AS MIMIC...SHOWS A DRY SLOT
THAT IS CUTTING UNDERNEATH GASTON AT THIS TIME AND TRYING TO CUT
OFF ITS MOISTURE SUPPLY FROM THE SOUTHEAST IN THE ITCZ. HOWEVER THERE
IS ALSO A PROTUBERANCE OF MOISTURE SOUTHWEST OF GASTON THAT MAY
RE-CONNECT IT WITH MOISTURE IN THE ITCZ. TWO...THE STRONG TUTT
LOW THAT IS MOVING WEST OVER PUERTO RICO IS PULLING MOISTURE IN
FROM THE SOUTHWEST. ITS REFLECTION AT MID LEVELS IS SOUTHEAST AND
IS ALSO PULLING UP MOISTURE...AS EVIDENCED BY WATER VAPOR
IMAGERY...AND IS FILLING THE AREA AHEAD OF THE REMNANT LOW OF
GASTON WITH BETTER MOISTURE. WHEN THE LOW REACHES THIS SOURCE OF
MOISTURE IT IS EXPECTED TO REGAIN STRENGTH...AND THIS IS NOT
EXPECTED UNTIL SUNDAY NIGHT OR MONDAY. WHETHER IT IS SUFFICIENT TO
ALLOW GASTON TO REDEVELOP INTO A TROPICAL STORM...AS SOME
HURRICANE CENTER GUIDANCE SUGGESTS...REMAINS TO BE SEEN...BUT SEEMS
LIKELY.

&&

.AVIATION...
VCSH AND POSSIBLE -SHRA ACCOMPANIED BY BRIEF MVFR CONDS ARE
POSSIBLE FROM 05/02Z THROUGH AT LEAST 05/14Z ACROSS
TJSJ...TIST...AND TISX. PREVAILING VFR CONDITIONS ARE EXPECTED
ELSEWHERE THROUGH 05/14Z. AFTER 05/16Z...EXPECT SHRA AND TSRA
DEVELOPMENT ACROSS THE CORDILLERA CENTRAL...RESULTING IN LOCAL
MOUNTAIN OBSCURATIONS AS WELL AS BRIEF MVFR ACROSS TJMZ BETWEEN
05/17Z-05/21Z. LOW LEVEL WIND FLOW WILL CONTINUE FROM THE NORTH
NORTHEAST AT LEAST THROUGH TOMORROW AFTERNOON...SHIFTING MORE
EASTERLY DURING THE AFTERNOON HOURS.

[cycloneye]

Good morning. Important discussion to read about what may occur with Ex Gaston.


AREA FORECAST DISCUSSION...DELAYED
NATIONAL WEATHER SERVICE SAN JUAN PR
623 AM AST SUN SEP 5 2010

.SYNOPSIS...TUTT LOW WILL CONTINUE MOVING WEST NORTHWEST ACROSS
THE LOCAL AREA TODAY AND THEN AWAY FROM THE REGION TONIGHT
THROUGH MONDAY. UPPER LEVEL HIGH PRESSURE WILL EXTEND INTO THE
LOCAL AREA MONDAY NIGHT AND TUESDAY. THE REMNANTS OF TROPICAL
STORM GASTON ARE EXPECTED TO APPROACH THE LOCAL AREA TUESDAY AND
THEN MOVE NEAR OR ACROSS THE LOCAL ISLANDS TUESDAY NIGHT THROUGH
WEDNESDAY OR THURSDAY...POSSIBLY AS A TROPICAL CYCLONE.

&&

.DISCUSSION...AS NOTED ABOVE...TUTT LOW OVER THE FA AT THIS TIME
AND WILL CONTINUE MOVING STEADILY WEST NORTHWEST THROUGH MONDAY.
ASSOCIATED LOW TO MID LEVEL REFLECTIONS APPEAR TO BE LOCATED JUST
WEST OF THE LEEWARD ISLANDS...AND WILL MOVE ACROSS THE U.S.
VIRGIN ISLANDS AND PUERTO RICO TODAY THROUGH EARLY TONIGHT. THESE
FEATURES WILL COMBINE WITH AVAILABLE MOISTURE...LOCAL EFFECTS AND
UPPER DIVERGENCE FROM THE TUTT...TO CONTINUE TO PRODUCE SOME
CLOUDINESS...SHOWERS AND A FEW THUNDERSTORMS ACROSS THE LOCAL
ISLANDS TODAY...BUT WITH THE FOCUS BEING OVER THE CENTRAL AND
WESTERN INTERIOR...WEST AND SOUTHWEST SECTIONS OF PUERTO RICO
THIS AFTERNOON. A COUPLE OF THUNDERSTORMS COULD BECOME STRONG TO
SEVERE...WITH STRONG AND GUSTY WINDS...HAIL AND FREQUENT CLOUD TO
GROUND LIGHTNING...AS WELL AS PERIODS OF HEAVY RAINFALL. FOR
MONDAY...EXPECT SIMILAR CONDITIONS TO TODAY WITH SOME
CLOUDINESS...SHOWERS AND A COUPLE OF THUNDERSTORMS AGAIN...BUT
THIS TIME FOCUSED OVER THE CENTRAL AND WESTERN INTERIOR...WEST
AND NORTHWEST SECTIONS OF PUERTO RICO. FOR MONDAY NIGHT...
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED.

THAT WAS THE EASY PART OF THE FORECAST. FOR TUESDAY THROUGH
WEDNESDAY AND PROBABLY THURSDAY...THE LOCAL WEATHER WILL BE
DETERMINED BY THE REMNANTS OF TROPICAL STORM GASTON...AND EXACTLY
WHAT THIS SYSTEM DOES. THIS REMNANT LOW OF GASTON WAS LOCATED NEAR
LATITUDE 16.5 NORTH AND LONGITUDE 49.5 WEST EARLY THIS MORNING AND
WAS MOVING WEST AT NEAR 12 KNOTS. THERE REMAINS AN ABOVE NORMAL
AMOUNT OF UNCERTAINTY WITH THE LOCAL FORECAST FOR MIDWEEK. TPC/NHC
CONTINUES TO GIVE THIS SYSTEM A HIGH CHANCE OF RE-DEVELOPMENT TO A
TROPICAL CYCLONE AND INDICATE THAT IT COULD BECOME A TROPICAL
DEPRESSION LATER TODAY OR MONDAY. SATELLITE DATA INDICATE THAT THE
LOW LEVEL CIRCULATION REMAINS PRETTY WELL DEFINED BUT SHOWERS AND
THUNDERSTORMS HAVE BEEN AND REMAIN LIMITED...ESPECIALLY ON THE
EAST SIDE OF THE CIRCULATION...PROBABLY DUE TO THE ENTRAINMENT OF
DRY AIR (SAL). ASSUMING THE TUTT LOW CONTINUES MOVING AWAY AS
EXPECTED...THE SHEAR AHEAD OF THE SYSTEM SHOULD REMAIN FAIRLY LOW
(12 OR 13 KNOTS OR LESS) FOR THE NEXT FEW DAYS...AND IT IS NOW
MOVING OVER WARMER OCEAN WATER AND TOWARD AN AREA OF INCREASING
UPPER OCEAN HEAT CONTENT...PARTICULARLY FROM 57 OR 58 DEGREES WEST
AND WESTWARD THROUGH THE EASTERN CARIBBEAN.

TO COMPLICATE MATTERS...GLOBAL MODELS HAVE GENERALLY BEEN ALL
OVER THE PLACE WITH THIS SYSTEM...WITH THE GFS GOING FROM A
HURRICANE FORECAST 36 TO 48 HOURS AGO TO BASICALLY A WEAK LOW
ALONG A REMNANT TROPICAL WAVE AXIS WITH THE 05/00Z RUN.
INTERESTINGLY...MUCH OF THE NHC HURRICANE MODEL GUIDANCE CONTINUES
TO INDICATE A TRACK VERY NEAR OR ACROSS THE FA...WITH INTENSITY
GUIDANCE RANGING FROM A TROPICAL DEPRESSION OR LOW END TROPICAL
STORM (GFDL) TO A STRONG TROPICAL STORM TO EVEN A HURRICANE (SHIPS
AND LGEM). SO...AS MENTIONED THE UNCERTAINTY IS VERY HIGH AND WITH
THE TIMING APPARENTLY A BIT QUICKER THAN WHAT IT SEEMED A COUPLE
OF DAYS AGO...CUTTING DOWN ON POTENTIAL PREPAREDNESS TIME.

IRRESPECTIVE OF RE-DEVELOPMENT INTO A TROPICAL CYCLONE...WE
EXPECT SIGNIFICANT IMPACTS LOCALLY ANYWAY...WITH AN EXTENDED
PERIOD OF ACTIVE WEATHER...WITH FRESH TO STRONG WINDS...SHOWERS
AND THUNDERSTORMS WITH PERIODS OF HEAVY RAINFALL AND THE POTENTIAL
FOR SOME FLOODING...AND DETERIORATING MARINE CONDITIONS.

GIVEN THE LONG HOLIDAY WEEKEND AND THE UNCERTAINTIES WITH THIS
APPROACHING REMNANT LOW OF GASTON...ALL LOCAL EMERGENCY
MANAGERS...GOVERNMENT OFFICIALS...RESIDENTS AND VISITORS SHOULD
CONTINUE TO CLOSELY MONITOR THIS SYSTEM...STAY ABREAST OF THE
LATEST FORECASTS...AND BE READY TO TAKE QUICK ACTION...SHOULD IT
BECOME NECESSARY.

&&

.AVIATION...A VCSH OR -SHRA WILL BE POSSIBLE ACROSS THE VI...TJSJ
AND TJBQ THROUGH 05/14...WITH PREVAILING VFR CONDITIONS ALL SITES.
AFT 05/16Z...EXPECT SHRA AND TSRA DEVELOPMENT TO RESULT IN
LOCALIZED MOUNTAIN OBSCURATIONS ACROSS THE CORDILLERA CENTRAL AS
WELL AS BRING BRIEF MVFR CIGS AND VSBYS TO TJPS AND TJMZ FROM
05/17Z-05/22Z. PREVAILING LLVL NE WINDS OF 10-15 KTS ARE EXPECTED
TODAY.

&&

.MARINE...GENERALLY EXPECT WINDS OF 18 KNOTS OR LESS AND SEAS OF 5
FEET OR LESS ACROSS THE REGIONAL WATERS THROUGH MONDAY NIGHT.
WINDS AND SEAS WILL INCREASE SIGNIFICANTLY TUESDAY THROUGH
WEDNESDAY...AS THE REMNANTS OF GASTON APPROACH AND THEN MOVE
ACROSS THE LOCAL AREA. SHOULD GASTON RE-DEVELOP INTO A TROPICAL
CYCLONE...SIGNIFICANT CHANGES TO THE ONGOING LOCAL MARINE
FORECAST WOULD BE NECESSARY...PROBABLY WITH A VERY SHORT NOTICE.
THEREFORE...ALL LOCAL MARINE INTERESTS SHOULD CONTINUE TO CLOSELY
MONITOR LATER FORECASTS FOR UPDATES.

[Gustywind]

[Gustywind]

[Gustywind]

From Crown Weather Discussion
http://www.crownweather.com/?page_id=325
Tropical Weather Discussion
Issued: Sunday, September 5, 2010 905 am EDT/805 am CDT


Ex-Tropical Depression Gaston:
We continue to closely monitor the area of disturbed weather that was once Gaston. This system is currently located about 750 miles east of the Leeward Islands. Given the fact that environmental conditions are favorable for regeneration, this system will be closely monitored. There is a high degree of uncertainty on what this system may do over the next several days. Satellite imagery this morning showed a well defined low level circulation, however, there is a limited amount of deep convection associated with this system. This is likely due to the entrainment of dry air.

The synoptic forecast ahead of this system calls for an upper level trough of low pressure to back away over the next few days and for Ex-Gaston to remain in an area of fairly low wind shear. This system will also be tracking into increasingly warmer ocean waters, especially west of 58 West Longitude. This alone indicates that regeneration into a tropical cyclone seems likely over the next couple of days.

The one huge fly in the ointment, however, is the fact that the global model guidance has been all over the place with this system. The GFS model waffles back and forth between a weak area of low pressure and a significant hurricane in just 48 hours from now. The NHC track model guidance continues to indicate significant strengthening and a track that would take this system across the northern Leeward Islands during Tuesday and to just south of Puerto Rico on Wednesday and very near Haiti by the end of the week. As for the intensity guidance from the NHC models, the latest SHIPS guidance forecasts a moderate tropical storm by Tuesday morning and a hurricane by Tuesday night. The LGEM model forecasts Ex-Gaston to become a moderate strength tropical storm by Tuesday, a hurricane by Wednesday and a major hurricane by Thursday.

Given that this is a long holiday weekend, all emergency management officials, residents and vacationers in the Leeward Islands, Virgin Islands, Puerto Rico and Hispaniola should closely monitor this system and be ready to take quick action, should it become necessary. Those of you with friends and family in the Leeward Islands, Virgin Islands, Puerto Rico and Hispaniola, give them a heads up and let them know that there is a tropical system that they should closely monitor and that it could affect the northern Leeward Islands on Tuesday (just 48 hours from now!), Puerto Rico on Wednesday and Hispaniola by Thursday and Friday.
The next tropical weather discussion will be issued sometime on Monday.

Disclaimer: All forecasts herein are made to the best ability of the forecaster. However, due to standard forecasting error, these forecasts cannot be guaranteed. Any action or inaction taken by users of this forecast is the sole responsibility of that user.

[cycloneye]

2 PM TWO

SHOWER AND THUNDERSTORM ACTIVITY HAS BECOME BETTER ORGANIZED IN
ASSOCIATION WITH THE REMNANT LOW OF GASTON LOCATED ABOUT 700 MILES
EAST OF THE LEEWARD ISLANDS. ENVIRONMENTAL CONDITIONS APPEAR
CONDUCIVE FOR TROPICAL CYCLONE FORMATION...AND THE LOW COULD
REDEVELOP INTO A TROPICAL DEPRESSION AT ANY TIME TODAY OR TONIGHT
AS IT MOVES WESTWARD NEAR 15 MPH. INTERESTS IN THE LEEWARD ISLANDS
SHOULD MONITOR THE PROGRESS OF THIS SYSTEM. WARNINGS WILL LIKELY
BE REQUIRED FOR SOME OF THESE ISLANDS IF ADVISORIES ARE
RE-INITIATED. THERE IS A HIGH CHANCE...80 PERCENT... OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE AGAIN DURING THE NEXT 48 HOURS.

[msbee]

It's a rainy day here in St. Maarten and everyone thinks its Gaston and is worried

[Gustywind]

It's a rainy day here in St. Maarten and everyone thinks its Gaston and is worried

Thanks for these infos, and that seems quite understandble for most of the islands in the Northern... duE to the proximity of the strong wave/Low. I tkink that we should continue to monitor carefully ex Gaston us in the Leewards. Let's hope that Meteo-France will try to anticipate quickly this strong twave and even more (if it maintains this improvement seen the last hours, should it verifies too) during the next 12h-36H. The situation could become problematic if preventive alerts are not required very early. Quick action is not surely the best way to challenge a suddent TS or cane in vicinity of the islands. Stay tuned and hoping that nothing too bad comes from this feature.
Gustywind

[Macrocane]

Though the rains from TD 11E are not affecting Central America anymore, the bad newsare still coming from Guatemala where 40 people may have died becuase of landslides, until yesterday 21 people were confirmed dead, here is the link to the CONRED (emergency management of Guatemala), it's in SPanish though:

http://conred.gob.gt/index.php/boletines/informativos

[msbee]

I heard that about Guatemala, macrocane.
what a devastating loss of life for them

[alanstover]

Thanks for posting that, Macrocane. This has been a disaster for Guatemala. We got about 4 inches of rain at our location here, but some areas reportedly got up to 15 in. Bridges are washed out, roads are closed because of landslides, and people are displaced and missing, though I don´t have numbers at hand.

This tropical season has been tough on CA already this here, I sure hope we don´t get any big West Carib. storms that some folks are talking about.

Everyone in the Carribean, take care and be safe.

alan

[cycloneye]

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
947 PM AST SUN SEP 5 2010

.UPDATE...WINDS HAVE SHIFTED MORE EAST SOUTHEAST FROM THE 12Z
SOUNDING AND PRECIPITABLE WATER HAS INCREASED FROM 24 HOURS AGO
BUT INCREASED FROM 12 HOURS AGO. SHOWERS AND THUNDERSTORMS
CONTINUE IN THE ATLANTIC AND CARIBBEAN WATERS WITH A FEW SHOWER
INCURSIONS OVER CABO ROJO AND NORTHEAST PUERTO RICO. OTHERWISE ALL
SHOWERS OVER LAND HAVE DISSIPATED. ONE SHOWER WAS NOTED OVER THE
BEACHES IN SOUTHERN SAINT CROIX AND OVER THE WATERS THERE.


&&

.DISCUSSION...THE 05/18Z MODEL RUNS CONTINUE BRINGING THE REMNANT LOW
OF GASTON ACROSS THE CARIBBEAN WATERS SOUTH OF PUERTO RICO
TUESDAY NIGHT AND WEDNESDAY MORNING. ALTHOUGH DIFFICULT TO
TRACK...THIS LOW APPEARS TO BE MOVING AT ABOUT 9 TO 12 KNOTS DUE
WEST AND WOULD PASS SOUTH OF PUERTO RICO IN ABOUT THE SAME TIME
FRAME IF IT WERE TO CONTINUE UNCHANGED. THE NAM CARRIES THE LOW
JUST SOUTH OF PUERTO RICO IN A SOMEWHAT SPLINTERED FORM. THE GFS
CARRIES THE LOW ACROSS AS AN OPEN WAVE ABOUT 180 MILES SOUTH OF
SAN JUAN AT 08/06Z. THE ECMWF 12Z RUN LOSES THE LOW BUT SHOWS A
WEAK TURNING IN AN OPEN WAVE AT ABOUT 240 MILES SOUTH OF SAN JUAN
ALSO AROUND 08/06Z. THE UKMET 12Z RUN BRINGS THE LOW ACROSS
VIRTUALLY UNCHANGED...OR SLIGHTLY STRONGER...ABOUT 225 MILES SOUTH
OF SAN JUAN AT 08/02Z. THE FORMER MODELS HAVE WINDS AT 850 MB
WHICH RANGE FROM 10 TO 25 KNOTS...WHILE THE UKMET SHOWS WINDS UP
TO 35 KNOTS ACROSS PUERTO RICO AND THE U.S. VIRGIN ISLANDS ALSO AT
850 MB.

THE REMNANT LOW...CURRENTLY LOCATED ABOUT 860 MILES EAST
SOUTHEAST OF SAN JUAN...HAS BEEN STRUGGLING AGAINST A NUMBER OF
FACTORS WHICH MAY ULTIMATELY PROVE TO BE OVERWHELMING. GASTON HAS
BEEN NEARLY CUT OFF FROM ITS MOISTURE STREAM IN THE ITCZ AND IS
NEARLY ENCLOSED BY DRIER AIR AS EVIDENCED BY SHARPLY DEFINED
OUTFLOW BOUNDARIES MOVING EAST OUT OF THE MAIN CONVECTION. THE
AIR TO OUR EAST AHEAD OF THE LOW IS ALSO A LITTLE DRIER. WINDS AT
250 MB CONTINUE TO BE FAIRLY STRONG...VARYING FROM 25 TO 40
KNOTS. THIS SHEAR IS CLEARLY SEEN IN THE SATELLITE IMAGERY AS THE
TOPS OF THE CONVECTION IN THE LOW BLOW OFF TO THE WEST AT REGULAR
INTERVALS. IN ITS FAVOR...GASTON`S REMNANT LOW IS EXPECTED TO MOVE
OVER SLIGHTLY WARMER WATER IN THE NEXT 12 TO 24 HOURS AND
POSSIBLY INTO A MOISTURE PLUME FROM THE SOUTH OVER THE LESSER
ANTILLES. THIS PLUME IS PRESENTLY SPREADING SHOWERS OVER A WIDE
SWATH OF THE WINDWARD AND LEEWARD ISLANDS BUT WILL MOVE OVER
PUERTO RICO AND THE U.S. VIRGIN ISLANDS IN THE NEXT 9 TO 21
HOURS. THUS THERE IS STILL A POSSIBILITY THAT GASTON WILL BECOME
RE-INVIGORATED...AND SHOULD IT DO SO...IT IS NOT SO LIKELY TO
REMAIN SO FAR SOUTH OF THE AREA...AND COULD STILL PASS DIRECTLY
OVER THE AREA...THEREFORE ALL INTERESTED PARTIES SHOULD CONTINUE
TO MONITOR THE PROGRESS AND DEVELOPMENT OF THIS LOW.
HOWEVER AT THIS TIME AM CONSIDERING THE UKMET TO BE THE MODEL
THAT BEST DEPICTS WHAT THE LOW WILL DO...AND THE ONE THAT WAS BEST
INITIALIZED WITH THE APPARENT CONDITIONS OF THE REMNANT LOW.

FOR PUERTO RICO AND THE U.S. VIRGIN ISLANDS THIS MEANS INCREASING
WIND AHEAD OF THE LOW...WHICH IS EXPECTED TO CONTINUE ON A WESTWARD
COAST AND FLIRT WITH TROPICAL STORM STATUS...AS IT PASSES THROUGH
THE CARIBBEAN SEA TO THE SOUTH OF OUR FORECAST AREA. WE WILL
STILL BE IN THE STRONGER NORTHERN HEMISPHERE OF ITS INFLUENCE
WITH SHOWERS AND THUNDERSTORMS LIKELY AND WINDS THAT COULD REACH
20 TO 30 KNOTS IN OUR MARINE ZONES TUESDAY NIGHT AND WEDNESDAY.
THUS HAVE MASSAGED THE WIND GRIDS BEFORE AND AFTER THIS PERIOD TO
MORE CLOSELY RESEMBLE THE WIND FLOW PATTERN LEADING UP TO THE
PASSAGE OF A CLOSED LOW TO OUR SOUTH AND KEPT WINDS IN THE
OVERNIGHT PERIOD ON TUESDAY UNCHANGED...SINCE...FOR US...THE
PASSAGE OF A STRONG TROPICAL WAVE ABOUT 180 MILES SOUTH WILL
CLOSELY RESEMBLE THE PASSAGE OF A CLOSED LOW ABOUT 225 MILES
SOUTH. THIS SYSTEM IN EITHER FORM SHOULD BRING NUMEROUS SHOWERS
WITH SIGNIFICANT RAINS TUESDAY NIGHT AND WEDNESDAY...AND...DEPENDING
ON THE EXACT CONFIGURATION OF THE BANDS OF THE LOW AS IT LEAVES
THE LOCAL AREA...SHOWERS COULD LINGER ON THROUGH THURSDAY.

WINDS AND MOISTURE PATTERNS ARE UNREMARKABLE AFTER FRIDAY OR
SATURDAY WHEN MOISTURE BANDS LEAVE THE AREA. THE MODELS DO
DEVELOP ANOTHER SYSTEM NO LATER THAN FRIDAY 10 SEPTEMBER...POSSIBLY
FROM THE SYSTEM JUST LEAVING THE AFRICAN COAST NOW...WITH TOPS
NOTED AT MINUS 86 DEGREES IN THE 05/18Z SATELLITE PASS. THIS SYSTEM
IS NOT EXPECTED TO ARRIVE BEFORE WEDNESDAY...15 SEPTEMBER... AND
ITS TRACK IS QUITE UNCERTAIN AT THIS TIME. THE GFS TAKES IT NORTH
OF 20 NORTH BEFORE REACHING 50 WEST...BUT THE ECMWF LEAVES IT ON A
WEST NORTHWEST COURSE FOR GUADELOUPE. AND...IF THERE ARE
DEVELOPMENTS IN THE GULF OF MEXICO...IT WON`T EVEN BE THE NEXT
NAMED STORM!

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
400 AM AST MON SEP 6 2010

.SYNOPSIS...SUBTROPICAL RIDGE WILL BUILD WWD OVR THE NEXT FEW DAYS
AND HOLD THROUGH MID WEEK. REMNANTS OF GASTON STILL A THREAT TO
DEVELOP INTO A TC AND FCST TO PASS SOUTH OF PR/USVI EARLY WED MORNING.

&&

.DISCUSSION...ESE STEERING FLOW IN COMBINATION WITH AFTERNOON
HEATING AND SEA BREEZE CONVERGENCE SHOULD RESULT IN ACTIVE AFTERNOON
ACROSS NW PR. SUBSIDENCE WILL OVERSPREAD THE AREA THIS EVENING BUT
THIS WILL BE SHORT LIVED WITH FAR OUTER RAIN BANDS OF FORMER
TROPICAL GASTON LIKELY TO OVERSPREAD THE REGION AFTER MIDNIGHT.

FCST FOR TUE THROUGH EARLY THU WILL DEPEND ON THE EXACT TRACK OF
GASTON. SYSTEM WAS INITIALIZED AT 17.5N AND 54.2W AT 06Z
ACCORDING TO SAB WITH A MOVEMENT OF 275 AT 13 KT. MODELS SHOW
SYSTEM TAKING A WSW TRACK AS IT PASSES S OF PR/ST CROIX EARLY WED
MORNING. AN ASCAT PASS AROUND 06/0032Z INDICATED A LARGE SWATH OF
20-25 KT WINDS THAT EXTENDS AS FAR NORTH AS 21.5N. REGARDLESS OF
DEVELOPMENT...THIS SYSTEM WILL BRING WINDY CONDITIONS TO THE
REGION. TC WATCHES/WARNINGS OR WIND ADVISORIES MAY BE REQUIRED AT
ANY TIME PENDING NHC GUIDANCE. LATEST ECMWF/GFS GUIDANCE SHOW BULK
OF THE RAIN REMAINS SOUTH OF THE AREA BUT WILL NEED TO WATCH THIS
CLOSELY AS LATEST TPW IMAGERY SHOWS A LARGE AREA OF EXTREMELY
HIGH TPW VALUES NEAR 3.0 INCHES NEAR 17.0N AND 55.0W ASSOCIATED
WITH GASTON. WILL AWAIT NHC AND ETRAP GUIDANCE TO HAVE A BETTER
HANDLE ON RAINFALL POTENTIAL. IN ADDITION...AREA WILL BE UNDER
FAVORED NORTHEAST QUADRANT OF THE STORM WHERE TORNADOES ARE MOST
LIKELY TO OCCUR. PLEASE REFER TO PRODUCTS FROM NHC. EVERYONE IS
ENCOURAGED TO PAY CLOSE TO ATTENTION ON LATEST FORECAST AS
WATCHES MAY BE ISSUED AT ANY TIME.


&&

.AVIATION...PREVAILING VFR CONDS EXPECTED ACROSS ALL TAF SITES
THROUGH 06/16Z WITH PASSING SHOWERS POSSIBLE ACROSS
TKPK/TNCM...TIST/TISX...TJPS AND TJSJ. BTW 06/16Z-06/22Z BRIEF MVFR
CONDS WITH MOUNTAIN OBSCURATIONS EXPECTED IN AND AROUND TJMZ AND
TJBQ IN SHRA OR TSRA. AFT 07/06Z...CLOUDINESS AND SHRA/TSRA
ASSOCIATED WITH THE REMNANTS OF GASTON WILL OVERSPREAD ACROSS THE
REGION FROM THE EAST. THIS WILL LEAD TEMPO MVFR CONDS AND BREEZY TO
GUSTY WINDS IN THE VICINITY OR AROUND TNCM AND TKPK. TS CONDITIONS
POSSIBLE TUE NIGHT AND WED.

&&

.MARINE...WILL ISSUE SCA FOR ATLC WATERS FOR 20-25 KT WINDS AND
SEAS OF 6-8 FEET. THIS COULD BE QUICKLY CHANGED TO TS WATCH
DEPENDING ON WHAT NHC DOES WITH GASTON.

&&

[FireBird]

Alan, so sorry about Guatemala. The news has indicated 38 confirmed dead, and a halt to rescue operations because of continued poor weather. My heart goes out to the affected families, and we all hope that some fair weather will come your way soon to allow the journey to recovery to begin.

[bvigal]

Devastating news from Guatemala!

Great job by NHC/SJU on desribing possibilities with Gaston!

Am just amazed at how many people were grumbling and groaning about their damage in Earl, like someone had promised them the winds would only reach a certain peak! One prudent mariner explained it to me: "They are really just lazy and don't want to do the preparation "just in case". Then, when it's over and they had damage, they look for someone to blame."

So having heard an earfull of that this weekend, and days after posting about winds on http://www.storm2k.org/phpbb2/viewtopic.php?f=59&t=109232 thread, decided to mention in this morning's weather blurb. (quoting, because it changes too often and would make no sense later, also, the live links change and files are erased daily - did save the guru illustration)


"Monday 6 September, 8:30amAST - Flood Advisory portions of eastern PR, Small Craft Advisories pre-posted for Tuesday morning, Small craft precaution z710; Abbreviated Marine Forecast. No other watches, warnings or advisories in effect time of posting. For latest please check NWS SJU.

Current conditions: surface map, satellite, vis, PW product, SAL product, (no radars: NWS-TJUA, MFrance, St. Martin all down) 5am TRMM sat pass over Gaston shows enlongated system with precip to the NW of center. Winds over the area range from ENE to SSE (St. Croix SRB). Required reading: this morning's Discussion from NWS/SJU note the confirmation, location of winds 20+ kt far removed from ex-Gaston, and the anticipated track, weather hazards, as well as "EVERYONE IS ENCOURAGED TO PAY CLOSE TO ATTENTION ON LATEST FORECAST AS WATCHES MAY BE ISSUED AT ANY TIME."

Discussion specifically mention tornados, very good job! How much wind in a tornado? Well it isn't graded by Category 1, 2, etc. If a tornado, frequent in tropical cyclones, goes over you, plan on Category 5 winds! Don't be one of those (many in BVI recently) who complains after the damage to your property, like someone promised you the winds would not go over a certain limit! Another important note about winds - it's GUSTS that matter, which do the damage, not sustained winds. And those are calculated at sea level. The higher up you go, the more the wind. So, for instance, if a storm predicts 55kt winds and gusts to 65kt and you live 1000ft up on a mountain, 75-80kt gusts are quite reasonable.

Another sensible warning to those windguru fans out there. You are looking a forecast for one point on the map, about halfway to Anegada from Tortola. Yesterday the 06Z NAM had Gaston a small TS right over that point, wind and rain accordingly. The 12z run shifted Gaston slightly north, resulting in a product with winds under 10kt and no rain. Please keep in mind that models do change, and even normal variation in track/intensity can radically change what you see for that one spot. It is not the most reliable source for small cyclonic systems. Models are helpful, but they lag behind actual conditions by several hours. It's always better to look at satellite, and take the time to read what the human experts have to say."

[Gustywind]

[msbee]

Gusty
are you watching this? what does meteo france say?
recon plane in there now i think

[Gustywind]

Gusty
are you watching this? what does meteo france say?
recon plane in there now i think

Yeah i'm watching it Msbee, and very carefully! Meteo-France has issued an Yellow alert for both islands Guadeloupe and the Northern Leewards since this morning 9AM for a risk of strong showers and tstorms.

[msbee]

ok.
keep me informed please if anything changes
thanks
barbara