Caribbean - Central America Weather

[cycloneye]

Sundays discussion of 99L by Rob of Crownweather:

This post is NOT AN OFFICIAL FORECAST and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org. For Official Information please refer to the NHC and NWS products.

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

Invest 99L Located In The Central Caribbean Likely To Become Tropical Storm & Possibly Hurricane Sandy This Week; Jamaica, Eastern Cuba, Hispaniola, The Bahamas & Possibly South Florida May Be Impacted By 99L/Sandy

Sunday, October 21, 2012 8:51 am
by Rob Lightbown

Invest 99L, which is an area of low pressure located over the central Caribbean is gradually becoming better organized this morning. Satellite loops this morning showed a definite increase in thunderstorm activity, especially on the eastern side of the low pressure system. Based on this and the fact that 99L is in a environment that is favorable for development, I think that this system will become a tropical depression by late tonight or Monday morning and then Tropical Storm Sandy by Monday evening or at the very latest Tuesday morning.

The various forecast guidance has shifted considerably further west in the forecast track of Sandy, especially once it gets north of Haiti and Cuba. It seems that the guidance is trending towards the Canadian model and this is potentially not so good news for the Bahamas, south Florida and potentially coastal sections of the southeastern US, Mid-Atlantic states and the northeastern US. Let’s take a quick look at each of the latest model guidance members:

The GFS model forecasts that Sandy to be to track over Jamaica on Wednesday, eastern Cuba on Thursday and then across the central and northwestern Bahamas on Friday coming quite close to southeastern Florida by Friday evening. From there, the GFS model forecasts that Sandy will phase with a strong trough of low pressure moving into New England on Sunday which if this verifies would bring very heavy rainfall and strong winds to much of New England on Sunday.

The European model forecasts that Sandy-to-be will track over Jamaica on Wednesday, eastern Cuba on Thursday and then across the central Bahamas on Friday and the northwestern Bahamas on Saturday. The European model does not phase Sandy with the eastward moving trough, but instead pulls it eastward out to near Bermuda by next Tuesday.

The Canadian model is the extreme of all of the model guidance in its phasing forecast. The Canadian model forecasts that Sandy will track just west of Jamaica on Thursday morning and then forecasts an extremely close brush if not landfall on southeastern Florida on Friday. The Canadian model also forecasts Sandy to phase with the eastward moving trough and become an extremely intense storm (central pressure of 962 millibars) near Virginia Beach by next Sunday morning.

It’s interesting to note that the UKMET model also hints at a track that is very similar to the Canadian model and shows it just west of Jamaica on Wednesday evening and then near the southern end of Andros Island in the Bahamas by Thursday evening.

So, here are my thoughts:
As I have really mentioned, I do think that 99L will be named Sandy by Tuesday at the very latest and a track north-northeastward right across Jamaica as a moderately strong tropical storm seems likely right now. The timeframe for this would be Wednesday evening. From there, Sandy may turn more northward and it “feels” the trough of low pressure to its west and starts to get captured by that trough. This means a track across the central/northwestern Bahamas is possible from near the southern end of Andros Island to right across Great Abaco Island on Thursday night or Friday morning. Now, a caveat here: A track further west very near southeastern Florida on Friday morning is certainly possible and this is something that will need to be watched for very closely.

Beyond that, I have concerns that the forecast guidance are trending towards the idea of Sandy phasing into the eastern trough of low pressure and potentially becoming an intense coastal storm for the Mid-Atlantic states and New England. At this point, it is a possibility and we have more than enough time to watch for this potential.

One final thought: Late season tropical storms and hurricanes in the Caribbean can be extremely fickle and difficult to forecast. If we take a look at climatology for Caribbean storms in late October, they tend to take a north-northwesterly track towards south Florida. Additionally, late season storms are notorious slow moving systems and do not escape out the Caribbean very quickly; so, it is plausible that the global models may be overdoing the track out of the Caribbean with this system. So, nothing is written in stone when it comes to 99L/Sandy and this is a system that bears very close scrutiny.

One thing that is for sure: 99L/Sandy is likely to bring heavy rainfall and life-threatening flash flooding and mudslides to Jamaica, eastern Cuba and Hispaniola for much of this week.

[cycloneye]

Sunday's discussion of 99L by Dr Jeff Masters:

A tropical wave embedded in a large trough of low pressure (Invest 99L) covers a large portion of the Central Caribbean between Hispaniola and the northern coast of South America. This storm has the potential to be a dangerous rainfall threat for Haiti, Jamaica, and eastern Cuba. The disturbance is headed west at less than 5 mph, is over very warm waters of 29°C, and is in a moist environment. 99L has a large area of heavy thunderstorms that have a good degree of spin. These thunderstorms are beginning to organize into spiral bands, as seen on visible satellite loops. However, the amount of heavy thunderstorm activity is about the same as yesterday, and there are no signs of a surface circulation. An Air Force hurricane hunter aircraft is scheduled to investigate 99L this afternoon, but I expect this flight will be rescheduled for later.


Forecast for 99L

Wind shear is a low 5 - 10 knots, and is forecast to be in the low to moderate range, 5 - 20 knots, through Tuesday. This should allow for some steady development of 99L, and there has been a good deal of model support for 99L becoming a tropical depression by Wednesday. Steering currents favor a continued slow westward movement for 99L through Tuesday. On Wednesday, a strong trough of low pressure to the north of 99L is expected to turn the storm to the north or north-northeast, which should put 99L in the vicinity of Jamaica on Wednesday and Eastern Cuba on Thursday. By Friday, 99L should be in the Central or Eastern Bahamas. It is unclear at this point whether or not the trough pulling 99L to the north will be strong enough to pull the storm all the way out to sea to the northeast; a narrow ridge of high pressure has the potential to build in over 99L late this week and force the storm west-northwest, with a potential threat to the western Bahamas and U.S. East Coast by next weekend. In their 8 am EDT tropical weather outlook, NHC gave 99L a 70% chance of developing into a tropical cyclone by Tuesday morning. 99L will be capable of bringing heavy rains of 5 - 10 inches, with isolated amounts of up to 15 inches in mountainous areas, to Jamaica and Haiti, Monday through Wednesday. Heavy rains will begin on Tuesday in Eastern Cuba, and spread northwards into the Central and Eastern Bahamas by Wednesday.

[cycloneye]

12z Surface Analysis.

[cycloneye]

Sat Oct 20-12 730pmET UPDATE

While the main cities of Kingston Norman Manley Intl and Montego Bay Sangster Intl Jamaica have not yet reported any significant rainfall today thus far at the airports, a complex of thunderstorms developed over SW portions of Jamaica and has been deluging this part of the island.... through 730pmET , 61mm of rain has fallen at Bluefields, Westmoreland on the SW coast of Jamaica!! This would be causing severe flooding for certain, we don't need the reports when they come in to know this. But this part of Jamaica has been unusually dry for the last month at least. Still, that's an inordinate amount of rain

-justin-

Hey there are you here in Jamaica right now?

He lives in Ottawa,Canada but he gets information from the islands, (I dont know how he gets those)

[cycloneye]

2 PM Tropical Weather Outlook remains at 70%

A BROAD AREA OF LOW PRESSURE...ASSOCIATED WITH A TROPICAL WAVE...IS
PRODUCING A LARGE AREA OF SHOWERS AND THUNDERSTORMS OVER THE
CENTRAL CARIBBEAN SEA. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE
CONDUCIVE FOR THE FORMATION OF A TROPICAL DEPRESSION DURING THE
NEXT COUPLE OF DAYS...AND THIS SYSTEM HAS A HIGH CHANCE...70
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS
AS IT MOVES SLOWLY WESTWARD AND BECOMES NEARLY STATIONARY WELL
SOUTH OF JAMAICA. HEAVY RAINS FROM THIS DISTURBANCE ARE LIKELY TO
SPREAD OVER JAMAICA...HISPANIOLA...AND EASTERN CUBA OVER THE NEXT
SEVERAL DAYS. THESE RAINS COULD PRODUCE LIFE-THREATENING FLASH
FLOODS AND MUD SLIDES...ESPECIALLY IN AREAS OF HIGH TERRAIN.

[cycloneye]

Tropical Cyclone Formation Alert


WTNT21 KNGU 211530
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE
WITHIN 100 NM EITHER SIDE OF A LINE FROM 14.8N 76.0W TO 14.8N 78.9W
WITHIN THE NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT
IMAGERY AT 211200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 14.7N 75.5W. THE SYSTEM IS MOVING WESTWARD AT 07 KNOTS.
2. REMARKS: CURRENT MODEL GUIDANCE IS DEPICTING INTENSIFICATION OF
A TROPICAL WAVE LOCATED OVER THE CENTRAL CARIBBEAN SEA. AT 211200Z,
SATELLITE IMAGERY INDICATED AN AREA OF INCREASED THUNDERSTORM ACTIVITY
THAT HAS PERSISTED OVER THE LAST 24 HOURS. WARM SEA SURFACE TEMPERATURES
OF 83 TO 85 DEGREES FAHRENHEIT IN CONJUNCTION WITH A FAVORABLE UPPER AIR
ENVIRONMENT MAY ENHANCE DEVELOPMENT OF THIS SYSTEM INTO A TROPICAL CYCLONE.
3. THIS ALERT WILL BE UPGRADED TO WARNING OR REISSUED AS REQUIRED
BY 221530Z.//

[Caribwxgirl]

I was just looking at a satellite imagery and wondered whether that wasn't a spin I was seeing. Guess based on you post Cycloneye I was right. I'm getting a little better at interpreting this stuff

[Caribwxgirl]

It's raining here right now.

[cycloneye]

It's raining here right now.

Do you have a rain gauge to see how much rain falls in the next few days?

[cycloneye]

Good afternoon. The San Juan NWS discuss about the possible indirect effects for Puerto Rico from whatever develops during this week.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
400 PM AST SUN OCT 21 2012

.SYNOPSIS...AN ELONGATED MID TO UPPER LEVEL RIDGE WILL GENERALLY
REMAIN THE MAIN WEATHER FEATURE LOCALLY THROUGH MONDAY NIGHT OR
TUESDAY. THE RIDGE WILL HOWEVER BE GRADUALLY WEAKENING DURING
THIS TIME...AS A BROAD TROUGH BECOMES ESTABLISHED ACROSS THE
CENTRAL AND WESTERN CARIBBEAN AND THEN WESTERN ATLANTIC. AT THE
SAME TIME...ASSOCIATED SURFACE LOW PRESSURE IS EXPECTED TO DEVELOP
ACROSS THE CARIBBEAN SOUTH OF JAMAICA AND MOVE LITTLE THROUGH
TUESDAY...THEN LIFT MAINLY NORTH OR NORTH NORTHEAST ACROSS CUBA
AND THE BAHAMAS DURING THE MIDDLE TO END OF THIS WEEK.

DISCUSSION...FOR TONIGHT THROUGH MONDAY AND TUESDAY...ALTHOUGH IT
WILL NOT BE A PARTICULARLY UNSETTLED WEATHER PATTERN...THERE WILL
BE ENOUGH MOISTURE AROUND THROUGH THE PERIOD...TO PRODUCE SOME
CLOUDINESS...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS EACH
DAY.

THEREAFTER...WE WILL CONTINUE TO MONITOR THE EVOLUTION OF THE
AFOREMENTIONED SURFACE LOW PRESSURE SYSTEM. THERE ARE STILL
TIMING AND TRACK DIFFERENCES...BUT LATEST MODELS HAVE GENERALLY
SHIFTED TO THE WEST AND NORTHWEST KEEPING THE SURFACE LOW ON A
TRACK EVEN FURTHER TO OUR WEST THROUGH NORTH. NONETHELESS...IT
STILL LOOKS LIKE THE LOCAL AREA WILL HAVE THE POSSIBILITY OF THE
INFLUX OF DEEPER TROPICAL MOISTURE...WITH VEERING WIND FLOW WITH
HEIGHT AND FAVORABLE UPPER LEVEL CONDITIONS...IN COMBINATION WITH
LOCAL EFFECTS...INCLUDING SOUTH TO NORTH OROGRAPHIC LIFTING ACROSS
THE CORDILLERA CENTRAL. DESPITE THE WESTWARD SHIFT OF POTENTIAL
MODEL TRACKS...THE CURRENT INDICATIONS WOULD STILL YIELD SEVERAL
DAYS OF UNSETTLED WEATHER LOCALLY...PROBABLY BEGINNING EARLY
WEDNESDAY...AND THEN CONTINUING THROUGH THURSDAY AND FRIDAY AND
PROBABLY BEYOND. ALTHOUGH IT IS STILL TOO EARLY FOR MANY
DETAILS...THE "POTENTIAL" REMAINS FOR LOCALLY HEAVY RAINFALL...
POSSIBLY FLOODING...LOCALLY SEVERE WEATHER AND INCREASINGLY
HAZARDOUS WINDS AND SEAS AT SOME POINT DURING THE EVENT. STAY
TUNED.

&&

.AVIATION...MVFR CONDITIONS WILL PERSIST ACROSS TJPS AND TJMZ IN
SHRA/TSRA. ELSEWHERE...VFR CONDITIONS ARE EXPECTED WITH PASSING
SHOWERS AFFECTING THE TAF SITES FROM TIME TO TIME. SURFACE WINDS
WILL CONTINUE MAINLY EAST AT 10 TO 15 KTS.

&&

.MARINE...STILL EXPECT WINDS OF 18 KNOTS OR LESS AND SEAS OF 5
FEET OR LESS ACROSS THE REGIONAL WATERS THROUGH AT LEAST TUESDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 88 77 87 / 40 40 20 20
STT 77 87 77 87 / 40 40 30 30

[cycloneye]

18z Surface Analysis.

[msbee]

interesting blog post from Brian Norcross about 99 L

http://www.wunderground.com/blog/bnorcr ... ntrynum=13

[cycloneye]

8 PM Tropical Weather Outlook

A BROAD AREA OF LOW PRESSURE LOCATED A COUPLE OF HUNDRED MILES
SOUTH-SOUTHEAST OF JAMAICA IS PRODUCING A LARGE AREA OF SHOWERS AND
THUNDERSTORMS OVER THE CENTRAL CARIBBEAN SEA. ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO BE CONDUCIVE FOR THE FORMATION OF A
TROPICAL DEPRESSION DURING THE NEXT COUPLE OF DAYS AS THE LOW MOVES
SLOWLY WESTWARD AND BECOMES NEARLY STATIONARY WELL TO THE SOUTH OF
JAMAICA. THIS SYSTEM HAS A HIGH CHANCE...70 PERCENT...OF BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. HEAVY RAINS FROM THIS
DISTURBANCE ARE LIKELY TO SPREAD OVER JAMAICA...HISPANIOLA...AND
EASTERN CUBA OVER THE NEXT SEVERAL DAYS. THESE RAINS COULD PRODUCE
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES...ESPECIALLY IN AREAS
OF HIGH TERRAIN.

[Caribwxgirl]

It's raining here right now.

Do you have a rain gauge to see how much rain falls in the next few days?

The Met Service usually gives an update. So I'll report when they do.

[cycloneye]

It's raining here right now.

Do you have a rain gauge to see how much rain falls in the next few days?

The Met Service usually gives an update. So I'll report when they do.

Ok very good. Let's see how much rain falls in the island with this event,but hopefully nothing bad occurs.

[tropicana]

Sat Oct 20-12 730pmET UPDATE

While the main cities of Kingston Norman Manley Intl and Montego Bay Sangster Intl Jamaica have not yet reported any significant rainfall today thus far at the airports, a complex of thunderstorms developed over SW portions of Jamaica and has been deluging this part of the island.... through 730pmET , 61mm of rain has fallen at Bluefields, Westmoreland on the SW coast of Jamaica!! This would be causing severe flooding for certain, we don't need the reports when they come in to know this. But this part of Jamaica has been unusually dry for the last month at least. Still, that's an inordinate amount of rain

-justin-

Hey there are you here in Jamaica right now?

He lives in Ottawa,Canada but he gets information from the islands, (I dont know how he gets those)

thanks cycloneye for replying for me yeah caribgirl, i wish i was in jamaica now but no im not. i live in the Niagara Peninsula of southern ontario..i follow the weather in the caribbean very closely, i use all kinds of sources. Love reading this thread a lot though. Chockful of info. Cycloneye is a genius when it comes to the weather, i wish we could elect him president of puerto rico well hes president of this thread, no one will dispute. Stay safe caribgirl and keep us updated with the weather in Jamaica! You should get your own rain gauge.


UPDATE Sun Oct 21/12 630pmET I'm hearing no complaints in the weather world today from those in the Eastern Caribbean! Apart from the heat which isn't abnormal this time of the year. Just a few brisk showers overnight in St Vincent ( 2mm at Arnos Vale) and 5 mm at VC Bird Int in Antigua. A record 33mm of rain fell also at the airport in St Thomas Virgin Islands.
Dry air in the mid-levels of the atmosphere has kept any widespread showers at bay. There was an area of thunderstorms that developed over mainland Venezuela less than 100 miles SW of Trinidad..these formed in the heating of the day. Thunderstorms in the predawn and dawn hours this morning dropped 72mm of rain at Hato Airport in Curacao..that is close to 3 inches of rain! That must have sent the cacti into chaos LOL

-justin-

[Gustywind]

Very nice post Justin, i appreciate your daily job who is montruous. We could congrat our Superman President Cycloneye is an euphemisma ! This guy continues to be amazing each day, more than genius Justin... i've no words for that. Love you my carib friend, this thread is the perfect one to know all infos from the Carib! Be safe and dry caribgirl, we pray for Jamaica , keep the faith and fingers crossed.

[cycloneye]

Caribwxgirl, searching the net I found this from Jamaica in another forum.

October 21, 2012 at 5 p.m.

*** INCREASED RAINFALL EXPECTED FOR THE BEGINNING OF THE WEEK……WITH POSSIBLE STORM CONDITIONS BY MID-WEEK
***

An Area of Low Pressure, with an associated Tropical Wave, is currently southeast of Jamaica and is generating unstable weather conditions over the island and its territorial waters. The System which is expected to be southwest of Jamaica on Tuesday, and move over the island on Wednesday, currently has a high chance of becoming a tropical cyclone during the next 48 hours The forecast is for occasionally heavy showers and thunderstorms to impact the island particularly during the afternoon on Monday. On Tuesday through Thursday expect an increase in rainfall with possible stormy weather conditions developing by Wednesday

Fishers and other marine interests, especially those on the cays and banks, are strongly advised to exercise caution as the system remains over the area. All interests are urged to pay special attention to subsequent news releases from the Meteorological Service

[cycloneye]

00z Surface Analysis.

[cycloneye]

Thanks for those words Justin but what I am interested is to have a place where our fellow Caribbean and Central American friends can talk about the weather in their areas and this thread gives the opportunity to do just that. This thread has other things that are important as on the first post,there are plenty of radars and web cams from many places in the basin that people can see what is going on in real time. And of course when systems are a threat to the region,the reports about preparations,observations etc become the focus.