Belize Tropical Weather Outlook: May 27, 2016

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Belize NMS Forecast

6:00 AM in Belize, May 27, 2016

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

Tropical Atlantic Wide Infrared Satellite Image:

USA National Weather Service Forecast

May 27, 2016

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

Shower activity associated with the low pressure area located between Bermuda and the Bahamas continues to show signs of organization, and the circulation of the low has become a little better defined overnight. Environmental conditions are generally conducive for a tropical or subtropical cyclone to form later today or Saturday while this system moves west-northwestward to northwestward toward the southeastern United States coast. All interests along the southeast coast from Georgia through North Carolina should monitor the progress of this low. An Air Force Reserve hurricane hunter aircraft is scheduled to investigate the low this afternoon. The next special tropical weather outlook on this disturbance will be issued by 3 PM EDT this afternoon. For additional information on this system, see high seas forecasts issued by the National Weather Service.
* Formation chance through 48 hours...high...90 percent
* formation chance through 5 days...high...90 percent

Tropical Weather Discussion

...Special feature...
A 1012 mb low pressure is centered near 27n72w and is currently interacting with a broad upper-level trough, supporting scattered moderate convection within 180 nm of the northern semicircle of the low. A surface trough extends from 29n70w, to the low, to 24n73w. Environmental conditions are expected to be marginally conducive for a tropical or subtropical cyclone to form later today or Saturday while this system moves west- northwestward or northwestward toward the southeastern United States coast. There is a high chance for this system to develop into a tropical or subtropical cyclone over the next 48 hours. For more information on this system, please refer to the Atlantic tropical weather outlook under AWIPS/WMO headers twoat/abnt20.

...Tropical waves...
A tropical wave is emerging off of the coast of west Africa with the axis extending from 17n17w to 05n18w. The wave has a well- defined 700 mb trough axis as seen in the GFS analysis and the couple of west African rawindsondes. The wave also has a prominent maximum of moisture along its axis, as depicted by the total precipitable water imagery. Scattered moderate convection is present within 60 nm of the wave axis south of 08n.

A tropical wave in the central tropical Atlantic with an axis that extends from 14n50w to 03n50w, moving west at 15 to 20 kt over the past 24 hours. This wave has become difficult to track and only is weakly apparent in the suny-Albany tropical wave diagnostics at 700 mb. No significant deep convection is present currently associated with the wave.

A third tropical wave is located near the Windward Islands, extending from 16n62w to 07n62w. The wave is associated with a maximum of moisture and surface to 850 mb cyclonic curvature of the winds, though it is not apparent at 700 mb. Scattered moderate convection may be associated with the wave over northern Colombia.

Caribbean Sea... ...

An upper-level trough that extends into the western Caribbean is helping to induce scattered moderate convection near Jamaica, the southern Bahamas, eastern Cuba, and Haiti. A 1009 mb low that anchors the northeast pacific's monsoon trough is located near 11n75w in the southwestern Caribbean. Scattered moderate convection is within 120 nm of the low. The usual robust north- to-south pressure gradient over the Caribbean is substantially reduced, and the resulting tradewinds are only 10-15 kt across the Caribbean, except 20 kt near the coast of Colombia. The combination of the upper trough, abundant moisture, and the approaching easterly wave currently near the Windward Islands may produce scattered to numerous moderate convection with isolated to scattered deep convection over the central Caribbean including the Greater Antilles during the next two days. The tradewinds will remain relatively weak through Saturday.

Weather Underground Caribbean Forecast

Tropical cyclone development is not anticipated across the eastern Pacific on Saturday, while tropical activity ramps up over the western Atlantic. An area of low pressure is located between Bermuda and The Bahamas. This system has become more organized, and has a medium, 50% chance to develop into a tropical cyclone. Over the next 48 hours, this system will drift west northwestward over the western Atlantic. Meanwhile, thunderstorm activity will persist across eastern Mexico, focusing along the Sierra Madre Oriental Mountains. These thunderstorms will be driven by daytime heating, so expect the bulk of storms to fire up during the second half of the day. Mexico City, Mexico, will experience late afternoon and evening thunderstorms with a high of 79(F)/ 26(C). Most of western Mexico and the Yucatan Peninsula will experience warm and dry weather on Saturday. Cancun, Mexico, will be sunny with a high of 89(F)/ 31(C). Guadalajara, Mexico, will also be sunny with a high of 94(F)/ 34(C).

48 Hour Forecast – Favorable Environmental Conditions For Tropical Development

Infrared Satellite in Belize City

Possible Bonnie brewing near the Bahamas

5/27/2016 6:53:03 AM

An area of low pressure located a few hundred miles to the northeast of the Bahamas this morning will continue to track slowly to the west-northwest. The storm continues to be negatively impacted by an upper-level trough east of Florida. The upper-level trough is helping to enhance convection on the eastern side of the low-level circulation, but the strong shear associated with the trough is hindering the overall development of the storm.

The system will continue to track over a shallow layer of marginally warm water today, but the shearing over the storm will weaken over the next 12-24 hours and the storm may become a sub-tropical cyclone or perhaps Tropical Storm Bonnie late Friday or Friday night.

High pressure will build east of Bermuda Sunday and this will steer the system on a more northwestward track as it nears the South Carolina coast. Some computer models show the system stalling near the South Carolina coast and or slowly crawling to the northeast along the Carolina coast early next week.

The main impact will be moderate to heavy rainfall, increasing surf and beach erosion, and deadly rip currents along the Carolina coast over the holiday weekend.

120 Hour Forecast – Favorable Environmental Conditions For Tropical Development

Invest 91-L Is Expected To Become A Tropical Depression Or Tropical Storm Bonnie Either Later Today Or On Saturday & Will Impact Coastal Areas Of North Carolina, South Carolina & Georgia Throughout The Memorial Day Holiday Weekend With Rain & Gusty Winds
Rob Lightbown of Crown Weather Services

May 27, 2016

Invest 91-L Is Expected To Become Tropical Depression #2 Or Tropical Storm Bonnie Late Today Or On Saturday & Will Impact Coastal Areas Of North Carolina, South Carolina & Georgia Throughout The Memorial Day Holiday Weekend: Invest 91-L, which is located near 27.6 North Latitude, 72.9 West Longitude, is disorganized this morning even though the amount of wind shear impacting this system is lower today, compared to what it was 24 hours ago. Even though this system is disorganized, it has become a little more organized this morning. With the forecast for favorable environmental conditions over the next couple of days, I fully expect Invest 91-L to become Tropical Depression #2 and then very probably Tropical Storm Bonnie late today or during the day on Saturday. Finally, a reconnaissance aircraft is scheduled to investigate Invest 91-L to determine whether it has become a tropical depression or a tropical storm.

Looking at the environmental conditions around Invest 91-L, there is 10 to 20 knots of west-southwesterly wind shear impacting this system and this is more favorable for development as compared to the environment it encountered yesterday. It is apparent that wind shear values will range from 5 to 15 knots as Invest 91-L approaches the South Carolina coastline from later today through Saturday and I think that “all systems are go” for this to be a tropical depression and very probably a tropical storm as it moves along the South Carolina coast during Saturday and Saturday night.

The latest model track guidance are clustered around a path that takes it inland along the South Carolina coast between Charleston and Hilton Head Island during Sunday afternoon as a 45 to 50 mph tropical storm. The HWRF model is a little further north than the model cluster and forecasts Invest 91-L to come ashore between Charleston and Georgetown, South Carolina late Saturday night or Sunday morning as a 45 mph tropical storm.

Here Are My Thoughts: I think that when reconnaissance aircraft get into Invest 91-L and investigate it this afternoon, they will find that it is a Tropical Depression. In addition, I think that it is very likely that this system will strengthen further into Tropical Storm Bonnie sometime during the day on Saturday. As of right now, I’m thinking that we will see a landfall near Charleston, South Carolina around midday Sunday as a 45 to 55 mph tropical storm.

As we get into Monday and Tuesday, it looks likely, based on all of the data that I have looked at, that this system will track right along the coast of South Carolina and eastern North Carolina and slowly weaken before it becomes entrained into a eastward moving frontal boundary by the middle part of next week.

It looks unlikely that Invest 91-L will have enough time over water to become a upper end tropical storm or a hurricane and instead I think we should see it peak out at a moderately strong tropical storm.

Impacts For Coastal Georgia, Coastal South Carolina & Coastal North Carolina: Rain and gusty winds are forecast to gradually spread inland starting along the coast of eastern and southeastern North Carolina on Saturday afternoon and Saturday evening and spreading southwestward across coastal parts of South Carolina by late Saturday night and Sunday morning and possibly parts of the Georgia coast during Sunday. We are not forecasting excessive amounts of rainfall or excessive amounts of wind, but there is expected to be enough of a combination of rain and wind to produce a nasty weekend along the beaches and coast of eastern and southeastern North Carolina, South Carolina and parts of Georgia.

Rain Totals: Rain and gusty winds are forecast to gradually spread inland starting along the coast of South Carolina and North Carolina from Charleston to Cape Hatteras by late Saturday afternoon and Saturday night and then spread southwestward across the rest of the South Carolina coast by Sunday morning and then possibly as far south as Savannah, Georgia during the day on Sunday. Overall, we are not forecasting excessive amounts of rainfall or excessive amounts of wind, but there is expected to be enough of a combination of rain and wind to produce a nasty weekend across the beaches and coast of North Carolina and South Carolina.

Winds: The exact track and intensity of this system will dictate how much wind occurs across coastal parts of North and South Carolina. Right now, I would say prepare for wind gusts of 40 or 50 mph at times along the immediate coast of South Carolina and the immediate coast of southeastern and eastern North Carolina, especially from Charleston, South Carolina to Wilmington, North Carolina, from Saturday night through Sunday and into Sunday evening.

Everyone along the coast from Savannah, Georgia to Cape Hatteras, North Carolina should continue to closely monitor the progress of Invest 91-L as it will impact you during the upcoming Memorial Day weekend.

Invest 91L Information:

Model Track Forecast:

Satellite Imagery:

Northwestern Caribbean & Gulf Of Mexico May Need To Be Monitored For Tropical Development Between June 10th & June 20th: Once Invest 91-L/Bonnie-to-be is out of the picture sometime next week, our eyes may need to turn towards the northwestern Caribbean and Gulf of Mexico as this is an area to watch for possible tropical development between June 10th and June 20h as the long range forecast guidance continues to hint that the weather pattern could favor a tropical system to either form in the northwestern Caribbean and track into the Gulf of Mexico or just form in the Gulf of Mexico. In fact, the European and GFS model guidance are already starting to hint at this possibility with the European model forecasting an area of disturbed weather to move into the southern Gulf of Mexico by the week of June 6th and the GFS model guidance forecasting a tropical system tracking northeastward across the southern and eastern Gulf of Mexico around June 10th. It should be pointed out that a few of the ensemble members of the GFS model forecast the same idea of a tropical system tracking northeastward from the Yucatan Channel on June 8th to south Florida by June 9th and 10th. Also, the ensemble tropical cyclone probabilities from the GFS model reveal that there is an increased risk for tropical development in the southwestern Caribbean in about 10 days from now and the European ensemble guidance also hints at increased chances for tropical development in the southwestern Caribbean during the week of June 6th.

At this point, it is something to just keep an eye on and that tropical development in the western Caribbean or Gulf of Mexico is not a sure thing at all between June 10th and June 20th. Finally, I will be keeping you updated on the latest regarding this possibility in the coming weeks.

Tropical/Subtropical Depression Could Form Today in Northwest Atlantic
Jeff Masters

3:50 PM GMT on May 27, 2016

Formation of a tropical or subtropical depression appears imminent on Friday or Saturday in the waters between the Bahamas and Bermuda as Invest 91L moves west-northwest or northwest towards the Southeast U.S. coast. Should it become a named storm, it would be called Bonnie.

Satellite loops show that 91L has a pronounced spin near the surface that has improved in organization since Thursday--the circulation is less elongated, and more circular. However, there was only a modest amount of heavy thunderstorm activity that was not changing much in areal coverage associated with 91L on Friday morning. The latest pass from the ASCAT satellite showed an area of surface winds near 35 mph in the heaviest thunderstorms to the north of the center. Sea surface temperatures (SSTs) near 91L's center were about 26°C (79°F), which is 1 - 2°C (1.8 - 3.6°F) above average. These waters are only marginally warm enough to support formation of a tropical storm, and 91L has taken on some characteristics of subtropical system instead of a tropical system. As I explain in my Subtropical Storm Tutorial, a subtropical storm typically has a large, cloud free center of circulation, with very heavy thunderstorm activity in a band removed at least 100 miles from the center. The difference between a subtropical storm and a tropical storm is not that important as far as the winds they can generate, but tropical storms generate more rain.

Wind shear on Friday morning had fallen to the moderate range, 10 - 20 knots, increasing the odds of development. A large area of dry continental air lies to the west of 91L, and this dry air is interfering with development. A hurricane hunter aircraft is scheduled to investigate 91L on Friday afternoon.

Figure 1. Latest satellite image of 91L.

Figure 2. Predicted wind speeds for the Southeast U.S. at 2 am EDT (06Z) Sunday, May 29, 2016 from the 00Z Friday, May 27 runs of the European model (left) and GFS model (right). Both models had the storm just off the coast of South Carolina. Image constructed using our wundermap with the "Model Data" layer turned on.

A heavy rain threat for the Southeast U.S. coast
The 12Z (8 am EDT) Friday run of the SHIPS model predicted that wind shear would stay generally in the moderate range, 10 - 20 knots, for the next five days, which should allow some slow development of 91L. On Friday and Saturday, 91L will be traversing waters of 25 - 26°C (77 - 79°F), which should be just warm enough to allow development. The storm may get a small boost when it crosses the axis of the warm Gulf Stream current on Saturday afternoon. The system will have trouble with the large area of dry air to its west; if wind shear remains in the moderate range, 91L may have difficulty moistening its inner core enough to wall off this dry air. In their Friday morning (00Z) runs, our three top models for forecasting tropical cyclone genesis--the American GFS model, the European ECMWF model, and the British UKMET model--all showed the potential for Invest 91L to develop into a tropical or subtropical depression on Friday or Saturday. In a special Tropical Weather Outlook issued at 7:45 am EDT Friday, the National Hurricane Center bumped up their development odds in the 2-day and 5-day time ranges to 90%.

The models are not very gung-ho about intensifying 91L, and the system will have too little time over water to become anything stronger than a 55-mph tropical storm. Thus, heavy rain is the main concern from this system. Heavy rains should reach the coasts of South Carolina and southeastern North Carolina on Saturday afternoon or evening--though the heaviest rains from 91L will likely stay out sea to the storm's east, in a large band of heavy rain typical for a subtropical system. The Friday morning runs of our two top models for hurricane tracking, the GFS and European models, showed the center of 91L reaching the central coast of South Carolina near Charleston early Sunday morning or late Sunday afternoon, respectively. Steering currents will shift on Sunday evening, as 91L gets caught in the circulation associated with a trough of low pressure passing to the north, forcing 91L to turn to the northeast. The center of 91L will likely track inland along the coasts of South Carolina and North Carolina on Monday and Tuesday, spreading heavy rains of 2 - 4" along its path. It is uncertain at this time whether or not 91L will be able to spread heavy rains farther north into Virginia later in the week.

We'll have a post later today analyzing the annual NOAA seasonal hurricane forecast, which will be released late this morning.

Figure 3. A large area of rains exceeding 10” fell between Austin and Houston between 7:00 am CDT Thursday, May 26, and Friday, May 27, 2016. Image credit: NOAA/NWS Advanced Hydrologic Prediction Service.

From tornadoes to torrents: Rain records inundated in Texas
A large chunk of the upper-level low that lingered over the western U.S. most of this week began pushing onto the Southern and Central Plains on Thursday, triggering widespread severe weather. As opposed to the isolated, tornado-generating supercells earlier in the week, Thursday’s severe storms were far more widespread, but competition between the many storms helped cut down the ability of any one cell to become a cyclic tornado-producer. NOAA/SPC logged a preliminary total of 19 tornado reports on Thursday in Texas, Oklahoma, Colorado, Kansas, and Missouri, with no serious injuries or major damage reported. The highest-impact scare was at Kansas City International Airport, where passengers were herded from the three main terminals into tunnels and parking garages during a 20-minute evacuation. Near Dodge City, KS—not far from where multiple tornadoes struck on Tuesday—hail as large as softballs pelted an area south and east of Clark State Lake on Thursday evening.

Rain-cooled air from the Central and Southern Plains finally pushed back an incredibly rich southerly feed of low-level moisture from the Gulf of Mexico that had fueled severe weather all week. Shunted into Texas, the moisture fed several mesoscale convective systems (MCSs) that produced torrential rain on Thursday afternoon into Friday morning, especially between the Austin and Houston areas. The town of Brenham racked up an amazing calendar-day total of 16.62”, obliterating its previous record of 10.38” from October 17, 1994. Most of that rain fell in a 12-hour period from noon to midnight. All by itself, Thursday’s total would rank as the fourth wettest month in Brenham’s history, and it is larger than May's monthly record of 15.09” from May 2015 (the wettest month by far in state history). Weather records in Brenham extend back to 1897. The heavy rains led to several high-water rescues in the Austin and Bryan areas, and two people were missing as of Friday morning, according to Flash flood warnings continued through noon CDT Friday just east of Austin, where 6” to 10” of rain had reportedly fallen. More heavy rain is possible across southern Texas with additional MCS development later on Friday and Saturday.

Overall, the severe weather threat will continue dropping through the Memorial Day weekend, as both vertical wind shear and instability will be much less favorable for supercell formation. However, with a still-respectable amount of low-level moisture in place, there will be plenty of showers and thunderstorms across the central states, making for a damp-at-times Memorial Day weekend from Texas to Minnesota and Wisconsin. Long-range models suggest that heavy rain may recur through next week in some areas, Texas in particular.

Jeff Masters (tropical), Bob Henson (severe)

Figure 4. Projected 5-day rainfall totals from 12Z (8:00 am EDT) Friday, May 27, through 12Z Wednesday, June 1, 2016. Image credit: NOAA/NWS Weather Prediction Center

Invest 91L a Threat to Develop and Impact the Southeast U.S.

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Tropical Atlantic Wide Visible Satellite Image

Edited by Marty (Today at 10:40 AM)