Belize Tropical Weather Outlook: August 20, 2017

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Area wind information


Belize NMS Forecast

August 20, 2017

At 9:00pm Saturday night, the remnants of Harvey was centered near latitude 14.3N, longitude 71.8W or about 135 miles N of the northern tip of Guajira Peninsula Colombia. The remnants of Harvey was moving to the West at 22 mph with maximum sustained winds of 35 mph. 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 20, 2017

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

Showers and thunderstorms have increased this morning in association with the remnants of Harvey. Gradual development of this system is possible, and it could become a tropical cyclone once again as it moves west-northwestward across the central and northwestern Caribbean Sea during the next couple of days. Interests in northern Nicaragua, Honduras, Belize, and the Yucatan peninsula should monitor the progress of this system. An Air Force Reserve reconnaissance aircraft is scheduled to investigate this disturbance later today.
* Formation chance through 48 hours...medium...50 percent
* Formation chance through 5 days...medium...60 percent

A trough of low pressure located a couple of hundred miles north of Puerto Rico continues to produce disorganized showers and thunderstorms. Environmental conditions are expected to be unfavorable for development of this system during the next couple of days, but they could become slightly more conducive for development by midweek when the system is near the northwestern Bahamas or Florida.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...20 percent.

A large area of cloudiness and disorganized thunderstorms located about 1000 miles east of the northern Leeward Islands is associated with a trough of low pressure. This system is currently embedded in a dry air mass, and upper-level winds are expected to become too strong to support development in a day or so. Therefore, tropical cyclone formation is not likely while this system moves northwestward at about 15 mph.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...10 percent.

...Tropical waves...

A tropical wave extends its axis from 20N45W to 10N46W, moving west at 15-20 kt. Satellite imagery indicates a large area of cloudiness but convection is limited in association with this wave due to Saharan dust intrusion. This system coincides with a well defined 700 mb trough, and a high amplitude northward bulge of moisture is noted on the TPW product.

A tropical wave was introduced to this map over the eastern Caribbean, after analyzing upper-air soundings across the islands and model guidance. The wave's axis extends from 19N65W to 10N64W, moving west at 10-15 kt. Scattered showers are noted over the northern portion of the wave mainly north of 16N between 62W-66W affecting the Leeward Islands, the U.S. Virgin Islands, and Puerto Rico.

A tropical wave extends across the central Caribbean with axis extending from 19N72W to a 1008 mb surface low near 14N72W to 11N73W. This system was previously T.S Harvey. Scattered moderate convection has developed during the past few hours near the low center mainly from 12N-17N between 73W-77W. A fast westward motion is expected to continue with this system for the next couple of days as the wave moves along the southern periphery of the subtropical ridge.

A tropical wave is over the western Caribbean with axis extending from western Cuba along 84W to near 10N84W, moving west at 10-15 kt. The wave shows up very well on the TPW animation and 700 mb streamline analysis. Energy from the wave has fractured to the northeast and is analyzed as a surface trough currently located over the Florida Peninsula. The wave is enhancing showers near Honduras, Belize and adjacent waters.

...The Caribbean Sea...

Three tropical waves are moving across the basin. Refer to the section above for details. Moisture associated with these tropical waves will continue to affect the area increasing the likelihood of showers and thunderstorms today. Scatterometer data depicts moderate trades across the basin, with the strongest winds remaining east of 70W.

Climate Prediction Center’s Central America Hazards Outlook


48 Hour Forecast – Favorable Environmental Conditions For Tropical Development



Infrared Satellite in Belize City

Tropical wave that was Harvey looking better organized; watching couple other tropical waves
Accuweather

8/20/2017

Tropical Rainstorm Harvey is located at 14° N, -74.2° W with maximum sustained winds of 35 mph and gusts to 45 mph, moving W 16 mph mph, pressure 29.73 in / 1006 mb.

Tropical Rainstorm Gert is located at 49.5° N, -27° W with maximum sustained winds of 40 mph and gusts to 50 mph, moving ENE 25 mph, pressure 29.50 in / 998 mb.

A good deal of convection has developed around Harvey this morning, indicating that it might be regaining organized tropical characteristics. Tropical Rainstorm Harvey is approximately 250 miles south-southwest of Port-au-Prince Haiti and continuing west at about 16 mph. Harvey may become a tropical depression or tropical storm before it makes landfall by Tuesday morning in the Yucatan Peninsula.

Heavy rainfall with flooding and mudslides can be expected across northern portions of Honduras by Monday, as well as the Yucatan Peninsula on Tuesday. Depending on the degree of strength, there can also be damaging winds as Harvey approaches. This can lead to power outages and damage to weak structures.

Additionally, we are monitoring a tropical wave designated 92L. This wave is relatively weak and struggling with strong wind shear. 92L will move into a more conducive environment over the next couple days, but any organization is expected to remain very slow.

Elsewhere in the Atlantic Basin, we are watching another tropical wave nearly 1000 miles east-northeast of the Lesser Antilles. This wave is struggling with significant wind shear from an upper level low to the northwest of the system, as well as dry air tou the east-southeast. This will inhibit this system from becoming better organized.

We are also watching a robust tropical wave that has emerged off the African Coast. Despite the strength of the wave, wind shear will prevent any further organization of the system.



120 Hour Forecast – Favorable Environmental Conditions For Tropical Development

Harvey Will Move Across The Caribbean This Weekend With Tropical Storm Conditions Expected Across Honduras, Belize & The Yucatan Peninsula From Monday Through Tuesday; Invest 92-L Will Head For The Bahamas Early Next Week & Will Be Monitored Closely For Signs Of Development
Rob Lightbown of Crown Weather Services

August 19, 2017

Tropical Storm Harvey:
5 am EDT/4 am CDT Statistics:
Location: 13.8 North Latitude, 65.9 West Longitude or about 235 miles to the east-northeast of Curacao.
Maximum Winds: 40 mph.
Minimum Central Pressure: 1005 Millibars or 29.68 Inches.
Forward Movement: West at a forward speed of 21 mph.

Satellite imagery and analysis of environmental conditions indicates that the center of Harvey is being exposed by northerly wind shear of 10 to 15 knots. Most of the thunderstorm activity is being pushed to the east of the center. It appears that the storm is relatively weak in strength and will probably remain weak until it reaches the western Caribbean on Monday. Once it reaches the western Caribbean, it is expected to find itself in a more favorable environment for intensification before it moves inland into Belize and the Yucatan Peninsula on Tuesday as a 50-70 mph tropical storm.

By about Thursday, Harvey is expected to move into the Bay of Campeche and its track beyond this is somewhat in question. The model guidance has trended further north with the forecast track of Harvey when it moves into the western Gulf of Mexico. The GFS model guidance has trended north and forecasts that Harvey will make landfall in extreme northeast Mexico and south Texas on Friday. The Canadian model guidance also suggests a landfall in northeastern Mexico next Saturday. The European model guidance forecasts a landfall near Tampico, Mexico next Saturday. Most of the European ensemble members forecast a eastern Mexican landfall late next week into next weekend with only a couple of members forecasting a Texas landfall.

The reason why the model guidance diverge some on where Harvey may make landfall late next week is that they disagree on how much the storm will be impacted by a weakness in the ridge of high pressure over the southern United States. The guidance has been quite inconsistent with this forecast weakness and what sort of interaction it may have. For example, yesterday, the European model forecasted that Harvey would be pulled northward towards the Texas coast. The latest European model forecast has done a complete 180 and now forecasts the high pressure ridge to remain strong and send the storm into eastern Mexico.

At this point, I still think we are looking at a final landfall somewhere between Tampico, Mexico and Brownsville, Texas on Friday or Saturday of next week as probably a tropical storm. With that said, I urge everyone along the coasts of eastern Mexico and Texas from Veracruz to Houston-Galveston to keep a close eye on the progress and track of Harvey. Both scenarios of either a track westward into eastern Mexico or a track northwestward into the lower or middle Texas coasts are viable possibilities.

Everyone Across The Yucatan Peninsula, Belize & Northern Honduras: Tropical storm conditions, including up to 50 mph winds and heavy rainfall, are expected across northern Honduras on Monday and Monday night. For Belize and the Yucatan Peninsula, tropical storm conditions, including up to 60-70 mph winds, heavy rainfall and high surf, are expected to start after midnight Monday night and continue through Tuesday and Tuesday evening.

Model Track Forecast For Harvey:

Model Intensity Forecast For Harvey:

Satellite Imagery Of Harvey:





Invest 92-L Located About 300 Miles To The East-Northeast Of The Northern Lesser Antilles: Invest 92-L is less organized as compared to yesterday as its being impacted by 2 upper level low pressure systems – one near 27 North Latitude, 51 West Longitude and another near 26 North Latitude, 62.5 West Longitude. These upper level low pressure systems are imparting 20 to 40 knots of wind shear and causing a much more disorganized look to the disturbance. With that said, Invest 92-L is certainly trying to fight back as satellite imagery has shown new deep convection firing over the past couple of hours.

The environmental conditions around Invest 92-L are still expected to remain unfavorable through this entire weekend. By Monday and beyond, the environmental conditions may become more favorable for development in the area of the Bahamas and we will have to see what kind of shape this disturbance will be in and whether development may actually occur.

The GFS and European model guidance is on one end of the development spectrum and forecasts no development at all from Invest 92-L. The Canadian model is on the other end of the development spectrum and insists on significant development into a hurricane in the Bahamas by about Wednesday. The UKMET model is somewhere in the middle of the development spectrum and forecasts that development into a tropical storm may occur to the north of the Bahamas by the middle part of next week.

Here Are My Thoughts On Invest 92-L: The big question is whether Invest 92-L will be able to survive the strong wind shear that will impact it for the next couple of days or so. Visible satellite imagery certainly suggests that the wind shear is doing a number on the disturbance, although, it is trying to fight back with the new formation of deeper convection over the past couple of hours.

So, if Invest 92-L hangs on through this weekend and pushes through the strong wind shear that it is currently encountering, then it has the potential to become a tropical storm in the Bahamas starting around Monday and Tuesday.

There will be a couple of large scale weather features that will impact the track of Invest 92-L next week. The first weather feature is a upper level high pressure ridge which will set up across the eastern United States early next week and this will likely initially guide Invest 92-L towards south Florida. This may be short lived, however, as a trough of low pressure digs southeastward into the eastern United States and potentially causing this system to turn north and even northeastward and track near the US Southeast Coast during the middle to end of next week. Timing will be everything though – a quicker forward speed of Invest 92-L or a slower arriving trough into the eastern United States would mean this could make it to Florida or the eastern Gulf of Mexico. On the other hand, a slower forward speed of Invest 92-L or a quicker arriving trough means that this system could be turned north and northeastward into the open Atlantic instead.

Bottom line is that I expect no development from Invest 92-L this weekend due to unfavorable environmental conditions. From there, the development chances of Invest 92-L may begin to increase by Monday and Tuesday as this system pushes across the Bahamas within a more favorable environment. It should be noted though that development is highly dependent on how organized it still is by early next week and whether the shear takes too much of a toll on this disturbance.

I will be monitoring Invest 92-L for signs of development over the next several days and will continue to have updates for you. Everyone in the Bahamas, Florida and the US Southeast Coast should keep an eye on Invest 92-L in case it starts to develop during the early to middle part of next week.

Invest 92L Information:


Model Track Forecast:

Courtesy of NCAR Research Applications Laboratory

Satellite Imagery:






The next tropical weather discussion will be issued between 9 and 11 am EDT/8 and 10 am CDT Sunday Morning.



Wind Shear Rips into Tropical Storm Harvey
Jeff Masters, Category 6

August 19, 2017


Tropical Storm Harvey, 92L Struggling

 
Above: Visible-wavelength GOES-16 image of Tropical Storm Harvey at 1530Z (11:30 am EDT) Saturday, August 19, 2017. Northwesterly wind shear is blowing the tops off of Harvey’s showers and thunderstorms, as seen in the tendrils extending southeastward from the disorganized storm. GOES-16 data are preliminary and non-operational. Image credit: RAMMB/CIRA @ CSU.

Time has not been kind to Tropical Storm Harvey, which entered the Caribbean as a minimal tropical storm on Friday. Hurricane Hunters were unable to find a closed circulation within Harvey at the 850 mb level (about a mile high) on Saturday morning. Because a closed circulation was found near the surface, the National Hurricane Center kept Harvey classified as a tropical storm at 11 am EDT Saturday. That may be generous, as no winds above tropical-storm strength (35 knots) were found at flight level by the Hurricane Hunters. Continuity may be a factor in keeping Harvey a tropical storm, since it is likely to move into a more nurturing environment later this weekend.

Radar display of TS Harvey, 1515Z 8/19/2017
Figure 1. Radar image showing the disorganized rain showers of Tropical Storm Harvey at 11:10 am EDT August 19, 2017. Lightning strikes are shown as black squiggles. Image credit: Meteorological Department of Curacao.

Located about 125 miles north-northeast of Curacao at 11 am EDT Saturday, Harvey was racing westward at 22 mph. Harvey’s envelope of convection (showers and thunderstorms) had become much more fragmented and elongated, a byproduct of the storm’s rapid motion coupled with persistently strong wind shear of 20-25 knots. It is possible Harvey will be stretched to the point where it loses its closed surface circulation and becomes an open wave by late Saturday. Assuming Harvey survives till Sunday, it will be moving into the western Caribbean, where wind shear is predicted by the 12Z Saturday SHIPS model to drop to the 5-10 knot range. Mid-level relative humidity should increase from around 50% to greater than 70%. This will give Harvey a much more supportive environment for strengthening. Sea-surface temperatures will remain quite warm along Harvey’s path, around 29°C (84°F)—roughly 0.5°C above average. These warm waters are quite deep, providing ample oceanic heat content to enhance strengthening if Harvey does remain a tropical cyclone.

The leading global models are in fairly good agreement on Harvey’s general track over the next 3-5 days, but subtle shifts could make a big difference in Harvey’s strength and long-term future. Most of the ensemble members from the 0Z Saturday runs of the GFS and European models take Harvey near or just north of the Honduras coast on Monday, with a landfall late Monday or Tuesday in Belize or Mexico along the east coast of the Yucatan Peninsula. A few ensemble members bring Harvey into far northern Nicaragua or eastern Honduras, in which case Harvey would likely weaken and might never reach the Yucatan. The official NHC forecast from 11 am EDT Saturday tracks Harvey into Belize as a strong tropical storm on Tuesday morning.

Forecasts of surface pressure at 12Z 8/21/2017 from GFS ensemble run, 06Z 8/19/2017
Figure 2. Central pressure of Harvey at 8:00 am EDT Monday, August 21, as projected by the 6Z Friday run of the GFS ensemble modeling system. Each pair of red numerals denotes the location of Harvey’s center and the last two digits of Harvey’s central surface pressure, in millibars. Image credit: tropicaltidbits.com.

The bulk of track guidance brings Harvey into the southern Bay of Campeche by midweek. Although it would be a weak tropical storm at best by that point, Harvey would get another chance to reintensify. It may also be tugged northward by a weak upper-level trough that will move west across the Gulf of Mexico next week. As a result, Harvey’s track could angle more to the northwest with time, with a gradual slowing in forward speed. This slowdown and the uncertainty in steering flow add a great amount of uncertainty to Harvey’s future should it reach the western Gulf later next week.

Visible satellite image of 92L, 1615Z 8/18/2017
Figure 3. Invest 92L as seen by the GOES-16 satellite at 10:15 am EDT Saturday, August 19, 2017. 92L was struggling with dry air ingestion, and had a limited amount of heavy thunderstorm activity. Image credit: NOAA/CIRA/RAMMB. NOAA’s GOES-16 satellite has not been declared operational and its data are preliminary and undergoing testing.

92L weaker as it heads towards The Bahamas

Tropical disturbance 92L was located about 300 miles east-northeast of northern Lesser Antilles Islands, near 20°N, 58°W, at 8 am EDT Saturday, and was headed west to west-northwest at 15 - 20 mph. Satellite images on Saturday morning showed that the appearance of 92L had significantly degraded since Friday, with a limited amount of heavy thunderstorm activity and little evidence of low-level spiral banding or upper-level outflow. 92L continued to struggle with dry air ingestion, as seen by arc-shaped low-level cumulus clouds moving outwards from 92L’s heavy thunderstorms. When the thunderstorms of a tropical disturbance ingest a large amount of dry air at mid-levels of the atmosphere, the resulting strong downdrafts rob the storm of moisture and hit the ocean surface with a lot of momentum, kicking up arc-shaped bands of cumulus clouds as the downdraft spreads out along the ocean surface.

Conditions were marginal for development on Saturday morning, thanks to moderately high wind shear of 15 – 20 knots from two Tropical Upper Tropospheric Troughs (TUTTs)--one located a few hundred miles northeast of 92L, and one located a few hundred miles northwest of 92L. The trough to the northwest was pumping dry air into 92L’s circulation, keeping the mid-level relative humidity a very dry 45%, which is unfavorable for development. 92L did have warm SSTs of 28.5°C (83°F) to work with, though. The disturbance will pass a few hundred miles north of Puerto Rico on Sunday, and moisture associated with 92L will bring heavier-than-usual showers and thunderstorms to Puerto Rico, the Virgin Islands, and northern portions of the Dominican Republic on Sunday afternoon and Monday afternoon. A continued west-northwest motion for 92L is expected through Wednesday, with heavy rains from the system spreading into eastern Cuba and the central Bahamas on Monday and Tuesday, and into the northwestern Bahamas and Florida on Tuesday and Wednesday.

There was little model support for the development of 92L with the 0Z Saturday cycle of model runs. None of the operational runs of our three reliable global models for predicting tropical cyclone genesis—the GFS, European and UKMET models—developed the system, and fewer than 10% of the 70 members of the 0Z Saturday GFS and European model ensembles showed 92L developing into at least a tropical depression. The 12Z Saturday run of the SHIPS model predicted that 92L might find a more favorable environment for development beginning on Sunday, though, when the system might move into a region between the two TUTTS to its north, allowing wind shear to fall to the low range, 5 – 10 knots. Wind shear is predicted to remain low to moderate, 5 – 15 knots, Sunday through Wednesday. However, the atmosphere surrounding 92L will be dry through at least Tuesday, with a mid-level relative humidity near 50%. The best chance for 92L to develop may occur on Tuesday and Wednesday, when the system will likely encounter a moister environment near Florida. In its tropical weather outlook issued at 8 am EDT Saturday, the National Hurricane Center gave 92L 2-day and 5-day odds of development of 20% and 40%, respectively. The first hurricane hunter mission into 92L is scheduled for Monday afternoon.

Saharan Air Layer analysis, 12Z 8/19/2017
Figure 4. The Saharan Air Layer (SAL) analysis from 8 am EDT Saturday, August 19, 2017, showed that 92L and the tropical wave to its east were encountering dry Saharan air; Tropical Storm Harvey was in a moister environment. Image credit: University of Wisconsin CIMSS/NOAA Hurricane Research Division.

Strong tropical wave in the mid-Atlantic is no threat to land

Another tropical wave with the potential to develop into a tropical depression was located midway between the Cabo Verde Islands and Lesser Antilles Islands on Saturday morning, and was moving west-northwest to northwest at about 20 mph. Satellite images on Saturday morning showed the large wave had plenty of spin, but heavy thunderstorm activity was thin and poorly organized. Wind shear was light to moderate, 5 – 15 knots, and ocean temperatures were warm, near 27°C (82°F). The wave was beginning to encounter the dry air of the Saharan Air Layer, which was interfering with development.

As the wave heads to the northwest later in the week, it will encounter dryer air and high wind shear from a TUTT, making development unlikely. The 0Z Saturday operational runs of our three reliable models for predicting tropical cyclone genesis—the GFS, European and UKMET models—did not show development of this system over the next five days, but about 20% of the members of the 0Z Saturday GFS and European model ensembles did show development. The wave is likely to pass well to the northeast of the Lesser Antilles Islands and not threaten and land areas. In its tropical weather outlook issued at 8 am EDT Saturday, the National Hurricane Center gave this system 2-day and 5-day odds of development of 10% and 20%, respectively.



CLICK HERE for the website for Belize National Emergency Management Organization (NEMO)


Tropical Atlantic Wide Visible Satellite Image




Last edited by Marty; 2 hours ago.