Belize Tropical Weather Outlook: August 27, 2016

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Area wind information


Belize NMS Forecast

6:00 AM in Belize, August 27, 2016

At 3:00am Tropical Storm Gaston was located over the Atlantic near latitude 27.9N longitude 52.0W, or about 820 miles east-southeast of Bermuda. Gaston was moving northwestward at 15 mph with maximum sustained winds of 65 mph.
A weak area of low pressure located near the central Bahamas and Cuba remains disorganized. This system is moving slowly west-northwestward - at around 10 mph - and only has a small chance of becoming a tropical depression during the next couple of days as it moves into the eastern Gulf of Mexico

Elsewhere in the North Atlantic, the Caribbean Sea and the Gulf of Mexico, tropical cyclone formation is not expected during the next 48 hours.


Tropical Atlantic Wide Infrared Satellite Image:

USA National Weather Service Forecast

August 27, 2016

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical Storm Gaston, located about 800 miles east-southeast of Bermuda.

A weak area of low pressure located south of Andros Island in the Bahamas continues to produce disorganized showers and thunderstorms mainly to the south and east of its center. Upper-level winds are not conducive for significant development during the next day or so while the low moves west-northwestward through The Straits of Florida at about 10 mph. Environmental conditions could become a little more conducive for some development when the system moves across the eastern Gulf of Mexico next week. Heavy rains are likely to continue over portions of eastern and central Cuba today. Gusty winds and locally heavy rainfall are likely over portions of the Bahamas, and will spread into parts of southern Florida and the Florida Keys later this weekend. Interests elsewhere in Florida and the eastern Gulf of Mexico should continue to monitor the progress of this disturbance.
* Formation chance through 48 hours...low...20 percent
* formation chance through 5 days...medium...40 percent

A weak trough of low pressure located about a hundred miles south of the coast of southwestern Louisiana is producing disorganized shower and thunderstorm activity over the north-central Gulf of Mexico. Conditions are not expected to be conducive for development before this system reaches the coast of Texas on Sunday. However, heavy rainfall is possible along the Gulf Coast from Louisiana to southeastern Texas during the next few days. For additional information, please see products from your local National Weather Service office.
* Formation chance through 48 hours...low...10 percent
* formation chance through 5 days...low...10 percent

An area of low pressure centered about 130 miles southwest of Bermuda is producing winds of around 35 mph. While shower and thunderstorm activity has increased a little near the center during the past few hours, any significant development of this system is likely to be slow to occur due the proximity of dry air. This low is expected to move westward and then west-northwestward at about 10 mph toward the coast of the Carolinas during the next few days. For additional information on this system, see high seas forecasts issued by the National Weather Service.
* Formation chance through 48 hours...low...30 percent
* formation chance through 5 days...low...30 percent

Tropical Weather Discussion

...Special features...
Tropical Storm Gaston is centered near 27.9n 52.0w at 27/0900 UTC or about 715 nm east-southeast of Bermuda moving northwest at 13 kt. Estimated minimum central pressure is 995 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Scattered moderate to isolated strong convection is from 27n-31n between 49w-55w. Please see the latest NHC intermediate public advisory under AWIPS/WMO headers miatcpat2/wtnt32 knhc and the full forecast/advisory under the AWIPS/WMO headers miatcpat2/wtnt22 knhc for more details.

...Tropical waves...
Tropical wave in the east tropical Atlantic extends along 27w from 10n-15n moving west near 10 kt over the past 24 hours. Wave is embedded within an area of dry stable air, thus no associated showers or convection.

Tropical wave in the west Caribbean extends from 20n80w to 11n83w moving west 10 to 15 over past 24 hours. Wave coincides with a well defined 700 mb global model trough and is embedded within an area of deep moisture. Scattered showers and isolated thunderstorms are from 19n to the coast of Central America between the wave and 88w.

Caribbean Sea...

The upper ridge over the Yucatan Peninsula dominates the Caribbean south of 20n west of 72w while an upper low over the central Atlantic covers the remainder of the Caribbean. An upper trough extends from the west Atlantic over Cuba near 21n77w then west to the western tip of Cuba creating a diffluent environment to generate scattered showers and isolated thunderstorms within 90 nm along the South Coast of Cuba. Scattered showers and isolated thunderstorms are from 13n-18n between 69w-79w. The activity in the west Caribbean is due to the tropical wave. Tropical wave will move out of the Caribbean late in the weekend/first of next week.

Weather Underground Caribbean Forecast

Tropical cyclone activity will persist in the eastern Pacific and the Atlantic Basin on Sunday. Tropical Storm Gaston is located approximately 965 nautical miles east southeast of Bermuda, with maximum wind speeds at 65 mph (55 kts). The forecast track for Gaston takes this system northwestward over the central Atlantic. By Sunday, Gaston is expected to be upgraded to a category 2 hurricane, with wind speeds ranging between 96 to 110 mph (83 to 95 kts). High surf will affect portions of Bermuda. A weak area of low pressure is extending from eastern Cuba to the central Bahamas. This system has a low, 20% chance to develop into a tropical cyclone as it pushes west northwestward. Regardless of development, heavy rain and thunderstorms will batter Hispaniola, as well as eastern and central Cuba. An area of disturbed weather is located over the north central Gulf of Mexico. This cluster of storms has a low, 10% chance to develop into a tropical cyclone. In the eastern Pacific, Tropical Storm Lester is located 452 nautical miles southwest of the southern tip of Baja California, with maximum wind speeds at 60 mph (50 kts). The forecast track for Lester takes this system westward. By Sunday, Lester is expected to be upgraded to a category 1 hurricane, with wind speeds ranging between 74 to 95 mph (64 to 82 kts). Lester does not pose threats to any major land masses. Additionally, a broad area of low pressure is located 1,215 nautical miles east southeast of the Big Island of Hawaii. This system has a high, 90% chance to develop into a tropical cyclone as it moves west northwestward.


48 Hour Forecast – Favorable Environmental Conditions For Tropical Development



Infrared Satellite in Belize City

Tropical wave crossing eastern Cuba and the southern Bahamas; Gaston churns over open water
Accuweather

8/27/2016 5:47:47 AM

Tropical Storm Gaston is located at 27.9° N, -52° W with maximum sustained winds of 65 mph and gusts to 75 mph, moving NW 15 mph, pressure 29.39 in / 995 mb.

A robust tropical wave approaching the western Caribbean is causing showers and thunderstorms from eastern Cuba, northward to the central and southern Bahamas. Visible satellite shows a weak cyclonic circulation along the northern edge of the wave over the central Bahamas. These cyclonic circulations have come and gone over the past several days as they have tracked into dry and more stable air, causing them to weaken. Upper-level wind shear over the past several days has also been a negative factor against this system strengthening. However, wind shear is currently lessening ahead of the wave, leading to an uptick in showers and thunderstorms this morning.

The system will approach the Florida Straits and northern Cuba later today and could enter the southeastern Gulf of Mexico by Sunday. Weak upper-level wind shear will support development and possible strengthening along the way, but on the other hand, dry air in its path will prohibit development, so it remains to be seen how this feature unfolds over the weekend. Model consensus shows a path to the northwest and north across the eastern Gulf of Mexico the early to middle part of next week. It is not out of the question that this feature strengthens into a tropical depression or storm at some time.

The main impacts of this robust tropical wave will be flooding downpours and gusty winds across the central and southern Bahamas today and tonight, and then South Florida and the northern Bahamas on Sunday into Monday. Flash flooding and possible mudslides in the higher terrain will impact Cuba through this weekend. A track closer to Florida next week could lead to flooding rain along the west coast of Florida.

Elsewhere, Gaston remains a tropical storm over the open waters of the central Atlantic Ocean. Gaston will move across warmer waters and under less wind shear through the weekend and this should allow Gaston to strengthen into a hurricane. There will be no direct impact to land through early next week. However, the tropical storm can bring increased swells, rough surf and dangerous rip currents to Bermuda this weekend.



120 Hour Forecast – Favorable Environmental Conditions For Tropical Development

We Are Watching Invest 99-L Near The Central Bahamas, Invest 91-L Near Bermuda & A New Tropical Disturbance That Will Move Off Of Africa Next Week
Rob Lightbown of Crown Weather Services

August 27, 2016

Invest 99-L Located Over The Central Bahamas: Invest 99-L continues to go through a 24 hour oscillation where during the morning hours, the thunderstorm activity suddenly flares up and is very robust for several hours during the daytime hours. This is followed by an almost total collapse of the thunderstorm activity during the evening hours which ends exposing the circulation that is Invest 99-L.

So, we are seeing the same thing this morning as thunderstorms have flared up again over the central Bahamas and some of these storms have fired right over the main area of circulation. Even with this convection that is firing right over the center of Invest 99-L, development is likely not going to happen anytime soon. The reason why is because as long as the thunderstorms fire up and then die down several hours later, development will not occur. For this system to develop and strengthen, we are going to have to see consistent and persistent thunderstorm activity that occurs near the center of Invest 99-L.

There is still 15 to 20 knots of northwesterly wind shear impacting Invest 99-L and it is dubious of whether the environmental conditions will improve dramatically. The reason why is because it appears that there is some drier air that seems to be pushing towards Invest 99-L from the northeast. So, even though this system is in a moist environment within moderate wind shear, there is the possibility that environmental conditions could become even more unfavorable for development and strengthening. On the other hand, there is an area of 10 knots or less of wind shear located from the Florida Straits into the southeastern Gulf of Mexico and this is where Invest 99-L is tracking towards and it is expected to be in this area of much lower wind shear by Sunday and Monday. The combination of this potentially lower wind shear and very warm ocean water temperatures in the Florida Straits makes me very nervous and definitely makes me not want to write this system off. I think that if we are going to see development from Invest 99-L, we will definitely see the first signs of it within the next 48 hours.

As I mentioned yesterday, any tropical wave that is producing thunderstorm activity in late August moving over very warm ocean waters and towards a more favorable wind shear environment is a system that needs to be monitored extremely closely, even though most of the model guidance forecasts no development. It is still too early to discount Invest 99-L and I think the key days for this system in determining whether it will develop or not will be Sunday and Monday.

For Those Of You In South Florida, The Florida Keys & The Bahamas: This tropical wave will bring locally gusty winds of up to 30 to 40 mph and heavy shower and thunderstorm activity today into Sunday across parts of the Bahamas and on Sunday through Monday and Tuesday across south Florida and the Florida Keys. Rainfall totals of 3 to 5 inches with locally higher amounts can be expected. This heavy shower and thunderstorm activity may then spread northward across the rest of the Florida Peninsula during Tuesday.

The model guidance continues to struggle mightily with how they handle Invest 99-L. I think one reason the models are having a hard time figuring out what Invest 99-L may do is due to the relative close proximity to Invest 91-L, which is located near Bermuda. The GFS model, for instance, tries to merge the energy from Invest 91-L with the energy from Invest 99-L near northeast Florida on Tuesday night. In addition, the model guidance continues to be in poor agreement on how much Invest 99-L may strengthen in the Gulf of Mexico.

The GFS and European model guidance are insistent on forecasting no development from Invest 99-L and as I already mentioned, the GFS model guidance seems to want to merge Invest 91-L and Invest 99-L near northeast Florida around Tuesday night.

The Canadian model guidance forecasts intensification in the eastern Gulf of Mexico on Monday and Tuesday into a tropical storm with a landfall near Pensacola, Florida on Wednesday. The UKMET model guidance also forecasts development and intensification in the southern and central Gulf of Mexico next week. Ultimately, the UKMET model forecasts this system to make landfall as a borderline tropical storm-hurricane on Friday in the western Florida Panhandle.

The HWRF model guidance continues to be not only very consistent and persistent in forecasting that Invest 99-L will become a named storm in the Gulf of Mexico next week, but it’s also been consistently the most extreme solution. It should be noted that the HWRF model has been notorious with strengthening systems way too much this year and its intensity forecasts should be used with an extreme amount of caution.

Here Are My Thoughts: I think the next couple of days, from today to Monday, will be crucial to whether Invest 99-L develops and strengthens or just remains a vigorous tropical wave. I still don’t think that we will see development today, however, Invest 99-L will need to be watched very closely for signs of development on Sunday as it moves into the Florida Straits and also on Monday when it is forecast to move into the southeastern Gulf of Mexico. On the other hand, if we end up seeing a very disorganized system that doesn’t get its act together by the time it moves into the southeastern Gulf of Mexico on Monday, then I think we can say that development probably will not happen at all and we can all breathe much easier.

For now, everyone along the northern and eastern US Gulf coast, from Louisiana to Florida’s west coast, should continue to pay close attention to the progress of Invest 99-L this weekend.

Invest 99L Information:


Model Track Forecast:

Courtesy of Weather Underground
Courtesy of Weather Underground
Courtesy of Weather Underground

Satellite Imagery:





Invest 91-L Located Near Bermuda: We are also keeping an eye on an area of low pressure, designated Invest 91-L, that is located about 130 miles to the southwest of Bermuda. This system is producing some shower and thunderstorm activity, however, development is expected to be very slow to occur. The reason why is because there is dry air located to the north and to the west of Invest 91-L and it is forecast to push through 30-plus knots of wind shear as it tracks westward towards the coast of the Carolinas over the next 2 to 3 days.

I think that we need to keep a very close eye on Invest 91-L starting around Tuesday as it pushes near the outer banks of North Carolina where environmental conditions are forecast to become favorable for development and development into a tropical depression or a tropical storm is very possible in a couple of days from now.

Much like what we are seeing with Invest 99-L, a majority of the global models do not forecast any sort of development from Invest 91-L. The HWRF model, on the other hand, forecasts this to become a tropical storm as it is moving near the outer banks of North Carolina on Tuesday and Wednesday.

Everyone in easternmost North Carolina and the outer banks of North Carolina should keep close watch of Invest 91-L as I think it has a decent chance of becoming a tropical storm by early next week.

Invest 91L Information:


Model Track Forecast:

Courtesy of Weather Underground
Courtesy of Weather Underground
Courtesy of Weather Underground

Satellite Imagery:





A New Tropical Wave Has A Good Chance Of Becoming A Tropical Storm When It Moves Into The Eastern Atlantic Next Week: A tropical wave now over west-central Africa near 3 East Longitude is forecast to push into the easternmost Atlantic around Tuesday or Wednesday. This is a tropical wave that will need to be watched very closely and I think it has a very good chance of becoming at least a tropical storm as it moves westward across the eastern Atlantic by late next week.

It is forecast, at this time, that there will be a strong upper level ride of high pressure that stretches across much of the Atlantic during the first couple of weeks of September. This is very important because it means that this system could track pretty far west in the Atlantic before it starts curving to the north and northeast.

Both the GFS and European model guidance are forecasting that the northernmost Lesser Antilles and Virgin Islands may be impacted by this system around September 6th. Not only that but the extended range European ensemble model forecasts that this is a system that could push pretty far west in the Atlantic possibly threatening the Bahamas and the US East Coast between September 8th and September 10th.

At this point, this is a tropical wave that we will be monitoring and at this point we’ll have to see how organized it is when it moves off of the coast of Africa around Tuesday and go from there. If we do see the large and sprawling upper level ridge of high pressure that is forecasted to be in place across the Atlantic during the first 2 weeks of September, then we could very well see a long tracked tropical cyclone. For now, however, it is something to just watch.




Little Change to 99L in The Bahamas; 91L Headed Towards North Carolina
Jeff Masters

August 27, 2016

There is little new to say about the saga of tropical wave Invest 99L, which continued to chug west-northwest at 10 mph through the northwestern Bahamas on Saturday morning towards South Florida and the Florida Keys. Satellite loops late Saturday morning showed little change in the storm’s organization and heavy thunderstorms since yesterday; 99L still lacked a well-organized surface circulation center and the amount of heavy thunderstorm activity was modest at best. Wind shear was a moderately high 15 - 20 knots, and 99L was still struggling with dry air, as seen on water vapor satellite imagery. Sea surface temperatures (SSTs) remained favorable for development, though, near 30 - 30.5°C (86 - 87°F). The Hurricane Hunter missions for Saturday afternoon have been cancelled.


Figure 1. Latest satellite image of 99L.


Figure 2. View from a webcam on Great Exuma Island in The Bahamas at 11:36 am EDT August 27, 2016. Heavy rains and gusty winds from 99L were affecting the island. Image credit: Bonefish’s Webcam.

Track forecast for 99L
There is now model consensus among the GFS, European, and UKMET models that 99L will continue on its current west-northwest track for the next three days and not turn to the north along the west coast of Florida. A strong ridge of high pressure now covering much of the Southeast U.S. and northern Gulf of Mexico will remain in place through Tuesday, which should keep 99L on its general west-northwest track at 5 - 10 mph. The storm will pass by South Florida and the Florida Keys on Sunday, bringing heavy rains to South Florida and Cuba on Saturday afternoon through Tuesday afternoon. The 7-day precipitation outlook from NOAA’s Weather Prediction Center (WPC) calls for a large area of 3 - 7” rains across South Florida over the coming week.

Intensity forecast for 99L
The SHIPS model on Saturday morning predicted that wind shear would fall slightly, to 10 - 15 knots, Sunday afternoon and beyond. SSTs will increase to 30.5°C (87°F) by Wednesday, and mid-level relative humidity was predicted to decrease from 65% to 55 - 60%. The shear and dry air may be strong enough to continue to keep 99L from organizing into a tropical depression, as predicted by NHC: in their 8 am EDT Saturday Tropical Weather Outlook, NHC gave 99L 2-day and 5-day odds of development into a tropical depression or tropical storm of 20% and 40%, respectively.

Two of our three reliable models for predicting tropical genesis, the ECMWF and GFS, continued to show no development of 99L into a tropical cyclone over the next five days in their latest 0Z Saturday (8 pm EDT Friday) runs. Our other reliable tropical cyclone genesis model, the UKMET, continued to predict that 99L would develop into a hurricane in the central Gulf of Mexico by the middle of the week. Even though the development odds for 99L have decreased markedly since the storm moved past Puerto Rico, we should not relax our guard with this storm until the UKMET falls in line with the GFS and European models. I will continue to mistrust 99L, since a strong tropical wave moving through the Gulf during the peak part of hurricane season is always a potentially dangerous situation.


Figure 3. Latest satellite image of Invest 91L off the coast of North Carolina.

91L headed towards North Carolina
An area of disturbed weather located about 500 miles east-southeast of North Carolina is moving west-northwest towards that state at about 10 mph, and was designated Invest 91L by NHC on Friday afternoon. Satellite loops on Saturday morning showed 91L had a vigorous but elongated surface circulation, and only a limited amount of heavy thunderstorms, which were removed from the center. A few showers from 91L were affecting Bermuda on Saturday morning, as seen on Bermuda radar. Conditions favorable for development include moderate wind shear near 10 knots, and sea surface temperatures (SSTs) of 29.5°C (85°F). These SSTs were about 2 - 3°F above average, and in July 2016, were the warmest July SSTs ever recorded for that area of ocean. However, 91L is embedded in area of dry air with humidities around 40 - 45% at mid levels of the atmosphere, and this dry air was stymying development.

Forecast for 91L
Steering currents favor a west-northwesterly motion for 91L at about 5 - 10 mph over the next three days. By Monday evening, 91L will begin spreading heavy rains along the coast of North Carolina, and the storm could move ashore on Tuesday before turning northeastwards, out to sea. That doesn’t give 91L a lot of time to develop, particularly since the atmosphere surrounding the storm is expected to remain quite dry. The 8 am EDT Saturday run of the SHIPS model predicted otherwise favorable conditions for development through Tuesday, with wind shear in the moderate range, 10 - 20 knots, and unusually warm SSTs near 29 - 29.5°C (84 - 85°F.)

The Saturday morning operational runs of our three reliable models for predicting tropical cyclone genesis, the European, GFS and UKMET models, did not show development of 91L, but the GFS ensemble forecast, done by taking the operational high-resolution version of the model and running it at lower resolution with slight perturbations to the initial conditions in order to generate a range of possible outcomes, had more than 50% of its twenty ensemble members predict that a tropical depression would form. Less than 20% of the 50 members of the 00Z Saturday European ensemble model forecasts showed development. In their 8 am EDT Saturday Tropical Weather Outlook, NHC gave 91L 2-day and 5-day development odds of 30%. Since the atmosphere 91L is embedded in is so dry, this storm should not be a huge rain maker for North Carolina relative to their usual tropical storms..

New tropical wave due to emerge from Africa on Tuesday may develop
The Saturday morning operational runs of our three reliable models for predicting tropical cyclone genesis, the European, GFS and UKMET models, all predicted that a strong tropical wave expected to emerge from the coast of Africa on Tuesday would develop into a tropical depression by late next week as it moves to the west at 15 - 20 mph. In their 8 am EDT Saturday Tropical Weather Outlook, NHC did not yet give 2-day and 5-day development odds for this system, but I give the wave 5-day development odds of 10%.


Figure 4. Latest satellite image of Tropical Storm Gaston.

Elsewhere in the tropics
The tropics are very busy this weekend, but that’s what we expect this time of year. In the Atlantic, we have Tropical Storm Gaston churning the waters about 750 miles east-southeast of Bermuda. Gaston is not a threat to land, but is expected to intensify into a Category 2 hurricane as it recurves to the northeast early in the week.


99L Remains Disorganized but Must Still be Watched; Tropical Low Bringing Rain to Gulf Coast; Invest 91L May Approach North Carolina



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Tropical Atlantic Wide Visible Satellite Image





Edited by Marty (Today at 12:23 PM)