Two systems close to merging in the eastern Caribbean

General overview 1400z 4th September 2013

Disturbance forty six is now centred over the extreme eastern Bay of Campeche, moving towards the Mexican coast at 5 knots. On this track, the disturbance is expected to move into mainland Mexico between Tuxpan and Tampico on Friday. Despite very fertile storm development conditions, this lost a lot of energy on its arduous cross-country trek and is struggling to organise. Slow progress across the Bay of Campeche is allowing the system to pick up water and there will be heavy rainfall and some squalls across the area for the next 48 hours.

Disturbances forty and forty seven are still flirting with one another either side of the Leeward Islands but have not yet made bodily contact. Disturbance forty is becoming better organised now and is centred about half a day's steaming to the west of the Leeward Islands and moving west at 7 knots. This has been very slow to track over the past 48 hours and as result, a pattern of squalls and heavy rain has become established. Disturbance forty seven – about a day's run east of the Leeward Islands is stalking ever closer to forty as it also heads west. The two systems are likely to consummate their mutual attraction into a single system near the southeast Bahamas in a couple of days. Conditions thereafter are encouraging for development. The chance of tropical development is now assessed to be 50 percent through the next 48 hours and 70 percent through the next 5 days. Regardless of development, the disturbances are expected to bring additional heavy rain to the Leeward Islands today and tomorrow. These rains are now starting to spread over Puerto Rico. The Dominican Republic is likely to receive heavy rains tomorrow. There is still a wide range of possibilities for the happy couple, dependant very much on which is the dominant partner post-merger, but a veer away from the eastern seaboard as a tropical storm seems to have the majority vote.

Disturbance forty eight is now a day west of the Cape Verde Islands, moving to the west-nor'west at 7 knots which will take it into unfavourable environmental conditions. Therefore, no development is expected.

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