Tropical Storm Watches Up in The Bahamas and Turks and Caicos for TS Emily
5:08 p.m. EDT
At 5 p.m. today, the Bahamian government posted watches for the Southeast Bahamas and the Turks and Caicos Island in advance of the arrival there on Thursday of Tropical Storm Emily. Emily, the 5th named storm of the 2011 season, is currently located near latitude 15.8°N and longitude 65.4°W or about 185 miles south of San Juan, Puerto Rico. This position is also about 600 miles southeast of Providenciales and Inagua. Emily is expected to move generally west-northwest and northwest over the next two to three days, crossing the island of Hispaniola and transversing Bahamian waters before moving northward into the wider Atlantic Ocean.
Emily had a rough birth; as Invest 91L the system was characterized by a broad area of surface low pressure and numerous ill-defined low- and mid-level centres forming, disippating, and reforming. However, at 7:30 p.m. on Monday 1st August the National Hurricane Centre was able to locate a relatively well-defined centre and Emily was named.
Despite this rather disorganized structure, Tropical Storm Emily brought gusty winds and heavy rainfall to Dominica, Martinique, and other Eastern Caribbean islands for more than 12 hours on 1st and 2nd August. This resulted in widespread flooding and numerous landslides in these islands. Reports from StormCarib.com suggest that at least one person died due to the flooding in Martinique.
This squally weather has since spread to the Virgin Islands and Puerto Rico. Since organization has improved somewhat in the last 12 hours, residents in the Dominican Republic and Haiti will likely expect more of the same during Wednesday and into Thursday of this week.
Emily's projected track takes the storm [or what's left of it after crossing the rugged Hispaniola landscape] up the length of the archipelago. In fact, the Bahamas has been in Emily's sights, so to speak, even before it was formally named. This is because there is a large and persistent Azores High to the northeast of us that has helped to maintain a similarly persistent ridge of high pressure across the sub-tropical Atlantic, across our area and at times even across Florida. However, this week a trough or area of low pressure will be pushing this high back towards the east, making a path of sorts around the edge of the ridge for Emily to follow.
The high pressure ridge in retreat on Friday, with TS Emily passing along its western edge.
While the exact track Emily takes is still somewhat uncertain, we can expect that most, if not all, of the Bahamas will experience some impact from the tropical storm.
What is of greater interest to most of us is the potential strength, or intensity, of Emily as she passes through our waters. Two factors are creating a great deal of uncertainty about the state Emily will be in by Friday morning.
First, TS Emily is still a very disorganized system. While it has improved in appearance and organisation since last night, it still is being disrupted by moderate shear and quite a bit of dry air in its environment. NHC officials are not expecting it to strengthen very much before it crosses Hispaniola on Wednesday.
Tropical Storm Emily at 5:15 p.m. on Tuesday, 2nd August 2011
Second, Emily's passage across the mountainous terrain of Hispaniola is likely to create some disruption to the storm's already tenuous circulation. Certainly on the forecast track Emily would find it difficult to strengthen while crossing the Dominican Republic and Haiti.
Map of Hispaniola, with the areas in tan, grey and white representing higher elevations.
However, once whatever is left of Emily crosses into Bahamian waters, the system will find conditions which are somewhat more conducive to restructuring than it met previously in the Caribbean. Sea surface temperatures are at their highest for the season; mid and low level shear is expected to be lower than seen in the Caribbean. Additionally, while rounding the ridge Emily may not move as quickly has she is expected to move tomorrow. Therefore there are still a lot of variables which may yet influence what Bahamians and Turks Islanders experience from Emily later this week.
Emily is expected to emerge into waters south of Inagua, Mayaguana and Providenciales on Thursday afternoon as a tropical depression. Some reorganization of the system is expected as it moves northwest over the archipelago on Thursday night, Friday, and into Saturday. Currently the NHC forecast does not call for sufficient strengthening to bring Emily up to hurricane force before departing our waters. However, the forecast models used by NHC still show varying scenarios ranging from complete dissipation to a category two hurricane near New Providence. This means that we should expect tropical storm conditions to impact our islands, but also insure that we are prepared to cope with hurricane conditions if they eventuate. This is particularly true in the Northwestern Bahamas, where any hurricane impacts would be most likely to occur.
Residents in the Southeast and Central Bahamas, along with the Turks and Caicos, will likely experience any impacts on Thursday night into Friday. These are expected to spread into the Northwestern Bahamas on Friday.
I'll continue updates regarding the progress of Emily in the comments section below.