Assuming the Worst: TD4 becomes Hurricane Danny

18 08 2015

Dale C. S. Destin |

Official_Track_ForecastThe first tropical cyclone (generic term for tropical depressions, storm and hurricanes) to threaten the Caribbean formed this morning. The tropical disturbance over the eastern tropical North Atlantic showed enough organization this morning to be upgraded to Tropical Depression Four (TD4).

The TD4official forecast from the U.S. National Hurricane Centre (NHC) has  the system developing into a Tropical Storm (TS) Danny later today and a Category 2 Hurricane by Sunday about 570 miles due east of Martinique and 650 miles east-northeast of Antigua.

ECMWF model

Notwithstanding the official forecast, arguably the most reliable weather model, the European Centre for Medium Range Weather Forecasting (ECMWF) model, does not seem to agree with it. The ECMWF model was quite early in forecasting the system becoming a TD but at most, so far, only gives it a 40 percent chance of becoming a tropical storm and less than 5 percent chance of becoming a hurricane.

Further, the ECMWF gives the system a less than 5 percent chance of impacting the Caribbean as a TS.

The ECMWF model seems to be expecting the abundance of dry air coming off of Africa and perhaps the return of hostile upper level winds to inhibit the TD.

At this time, I would like to view the Official forecast as nearing the worst case scenario and the ECMWF version of events to be nearing the best case scenario. I could be well wrong; however, given the impeccable track record of the European Centre model, it is difficult to accept that it could be is soo far off its game. It would be an unpleasant surprise to me and many.

Assuming the official forecast to be the more accurate, what would this mean for the Antigua and the Caribbean? We (the Caribbean) would need to prepare for a Category 2 hurricane with winds near 100 mph by Sunday with time to either strengthen further or weaken.

What is expected to be Hurricane Danny by then could impact islands as far south as Trinidad and Tobago or missing all the islands, passing a safe distance northeast of Antigua and Barbuda.



aal96_2015081812_intensity_earlyAt this time, residents in the Eastern Caribbean should at least be monitoring the potential Hurricane Danny and finalize their hurricane plans. If this goes according to the U.S. NHC forecast, a hurricane watch may be required for portions of the islands around Saturday with a warning around Sunday.

Again, assuming the worst case scenario, parts of the Eastern Caribbean could be in Hurricane Danny around Monday/Tuesday with the most likely path, according to the ECMWF and the U.S. Global Forecasting System (GFS) models, taking it across the northeast Caribbean passing in the vicinity of the Norther Windward Islands, the Leeward Islands, the Virgin Islands and Puerto Rico.

The system has the potential of producing destructive hurricane winds, stronger than those of Gonzalo of last year; flooding rainfall of two to six inches (51-153 mm), rough seas in excess of 12 feet (3.5 metres), significant storm surge flooding, and we cannot rule out tornadoes.

If we were to return to the forecast from the ECMWF as the best case scenario, the system would, at most, become a marginal tropical storm and bring needed rainfall to the Caribbean. Either way, some actions will likely be required this weekend to protect, life, property and livelihood due to hazards brought on by a TC Danny.

A lot can happen over the next several days; it is going to be interesting to see how things pan out; follow us and keep informed.



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