Barbados Meteorological Services
Charnocks ChCh
Weather Discussion

Initial to 4 days discussion based on Satellite imagery,BMS Radar composite,S.P.I.E products,GEM, GFS, WW3, UKMET and BMS WRF modeling, surface and upper air observations, Satellite derived products.

DATE: 20171118 PERIOD: Morning

David Best 4 Morning Once again during the night generally fair skies were recorded across Barbados and the islands of the Eastern Caribbean. However BMS Radar Composite and satellite imagery showed some echoes mainly in and around the central portion of the island chain , but mostly over the coastal waters. St Lucia reported some adjcent shower activity. Down south Trinidad and Tobago and the Guianas reported mainly fair skies. A relatively weak east-southeasterly low level flow was observed across Barbados and StLucia for most of the night , but the other island reported calm conditions. Meanwhile, seas remained slight to moderate in open water with swells peaking near 1.5m. High moisture levels and unstable atmospheric conditions , as a result of the combination of a persistent upper trough system to the west and a cold front passing across Hispaniola kept Puerto Rico and the Virgin Islands under cloudy skies and scattered shower activity and periods of rain. Further to the west Hispaniola recorded similar conditions plus some scattered thunderstorms. Further to the west Cuba and the Bahamas along with Jamaica to the south reported generally fair and tranquil weather.

An elongated area of low pressure continues to produce disorganized showers and thunderstorms over the central Caribbean Sea. Strong upper-level winds should limit development of this system while it drifts northward or northeastward during the next few days. Regardless of development, heavy rainfall is possible over portions of the northwestern coast of Colombia, Hispaniola, and Puerto Rico through the weekend.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 5 days...low...20 percent. Saturday: Weak low level trough will continue to affect the region. Hence, not much change to the overnight pattern is anticipated. However, some light winds in the lower levels may aid in the development of some afternoon localized showers over some islands.

Sunday: A drying of the lower levels is anticipated mainly over Barbados, the northern and central WIndwards, as a surface to mid level ridge dominates. Shower activity over those islands will be limited. Meanwhile, some low level moisture will remain over the Leewards and extreme southern Windwards and may still trigger a few scattered showers.

Monday: An approaching low level trough will transport some moisture over Barbados and the southern Windwards by day break. At the same time, a shearline feature will also maintain moisture over the extreme northern Leeward islands. As a result, occasionally cloudy skies along with some scattered shower activity is expected. Contrastingly over the other islands, a relatively dry and stable environment is predicted.

Tuesday: Not much change in the overall weather pattern is anticipated. However, some of the moisture over the northern Leewards will spread further southwards by early Wednesday.

It should also be noted, that a dry mid level environment along with a relatively strong subsident upper level pattern will persist over the next four days. Subsequently, the combination of these factors are predicted to hinder any significant shower activity. A frontal boundary and an induced surface trough are forecast to stall over the North Atlantic Ocean and near the local islands into next week. A deep layer southerly wind flow will pool tropical moisture over the islands inducing the development of showers and thunderstorms each day. Proximity of the elongated upper trough across the west
Atlantic will continue to erode the ridge aloft and provide good ventilation and instability to maintain potential for shower and thunderstorms development across the region through most of the weekend.A gradual improvement expected by Sunday into Monday. Only minor changes made to the inherited short term forecast for now.
The flash flood watch will continue for communities downstream from the Guajataca Dam, especially the low lying areas along the river through Saturday, and probably will be extended as long as the potential exists for dam failure due to flash flooding.
The combination of a weak frontal boundary, an induced surface trough, a southerly wind flow and good ventilation aloft will enhance showers and thunderstorm convection on Saturday. This activity could increase the risk for flooding as well as mudslides
along steep terrains mainly across the U.S. Virgin Islands and the interior and eastern sections of Puerto Rico.
A mid to upper level ridge is expected to build across the forecast area early next week and hold much of the forecast period. As this feature strengthens Mon-Tue, available low level moisture is expected to quickly erode with precipitable water values remaining
below the normal range Tue-Fri. At lower levels, east to east southeast winds will prevail across the local isles as a surface high dominates the central Atlantic. Under the aforementioned pattern, expect mainly fair and stable weather condition much of
the next week with trade wind showers across USVI and E Puerto Rico as well as some locally induced afternoon showers across west areas of Puerto Rico.