Watching Gabrielle, Remembering Fabian

Atlantic Analysis 201309060045UTC natl ir4-l
Trough near Bermuda (in red dashed lines) brings unsettled weather to Bermuda for now including gusty downpours and thunderstorms. Tropical Depression Gabrielle near the Dominican Republic as a red dot, tropical waves as red dashed lines. Rough upper level wind streamlines in turquoise showing rough locations of upper atmospheric troughs (eg. Tropical Upper-Tropospheric Trough or TUTT) and ridges.

Tropical Depression 7 quickly organized last night and strengthened into Tropical Storm Gabrielle. But this morning, the surface center of Gabrielle drifted to the west, towards the Dominican Republic. It’s mid-level center drifted north or even northeastwards towards Puerto Rico. This is a characteristic of a very disorganized/weak system – possibly a result of its interaction with the nearby tropical wave. Now Gabrielle has since weakened to a tropical depression. It consists of a low level swirl near the easternmost tip of the Dominican Republic, and a larger, broad circulation that extends from there far to the northeast of Puerto Rico associated with a separate tropical wave and enhanced by an upper atmospheric trough to the north. In the National Hurricane Center’s latest advisory at 6pm Bermuda time, they admit they are being generous with their classification as a tropical depression because of its disorganization, saying, “Gabrielle barely a tropical cyclone.” However, this isn’t stopping torrential, flooding rains from falling in Puerto Rico, the Dominican Republic and the Virgin islands.

The low level swirl that is Gabrielle should dissipate soon, however Gabrielle could reform further to the northeast – closer to the center of the broad circulation.  Another separate scenario involves a new tropical cyclone forming in the broad circulation of the tropical wave. In fact, the option for no new cyclone forming is still open and this area could remain a broad, disorganized tropical wave.

This mess of low pressure is drifting generally west-northwest and should begin to turn to the northwest then north in the coming days under the influence of a non-tropical trough near Bermuda and a cold front sliding off the United States East coast [see the figure above]. This is a track that takes it near Bermuda. So this area should be monitored closely regardless of tropical cyclone formation/reformation. Communication of hazards associated with disorganized systems like this can be confusing and communication despite being tweaked annually to address this issue. For now, as this system moves near Bermuda at least squally showers and thunderstorms can be expected and are included in the forecast. However, this is very likely to change as we get closer to the time of the event – this is the scenario disregarding tropical cyclone development/redevelopment.

In terms of intensity, if a new cyclone does form, timing becomes a very important factor. If a cyclone forms soon enough it will have a better chance of carrying its favorable upper atmospheric setup with it (as provided by the upper level ridge) allowing for potentially easier organization and a stronger cyclone. On the other hand, if it takes longer for a new cyclone to organize out of this area, it could leave this upper level ridge behind and move into a more hostile upper atmospheric environment (as created by an upper level trough to the north associated with the TUTT) and would continue to struggle with organization leaving a weaker cyclone.  Either way, if something were to develop it would be north of the Caribbean; over water that is plenty warm, and close enough to Bermuda to limit warning time. Constant vigilance to products issued by the Bermuda Weather Service and the National Hurricane Center could help protect life and property.

Remembering Hurricane Fabian 10 years on…

On August 28th, 2003 Tropical Depression 10 became a Tropical Storm and got the name Fabian. Late on the 29th, Tropical Storm Fabian had strengthened to a Hurricane. By the 30th, Hurricane Fabian’s continued strengthening put the storm at Major Hurricane Strength. Today, September 5th marks ten years since the destruction of Hurricane Fabian. Fabian made a direct hit on Bermuda as a category 3, major hurricane with 115-120mph 1-minute sustained winds. These destructive winds whipped up a storm surge estimated between 6 and 12feet (about 8 feet of inundation) with large battering waves that caused extensive coastal erosion, flooding, and subsequent damage including that to the causeway and airport. Winds, tornadoes, and vortices embedded in the storm’s circulation caused isolated wind damage that far exceeded expectations including that in parts of St. George and Southampton Parishes, otherwise widespread structural damage, and almost complete  vegetative damage was done by the wind. Official instruments were compromised by the storm surge’s inundation, but official estimates put sustained winds at 120mph with gusts to 150mph during the peak of the storm. Tragically, Hurricane Fabian is blamed for four deaths in Bermuda, and $300million in damages.

While we remember Hurricane Fabian, remember to stay tuned to the tropics and be prepared in the event of another powerful storm by following emergency information.

Some wind information sourced from the National Hurricane Center’s Tropical Cyclone Report on Hurricane Fabian 2003:

Hurricane Fabian Wind Reports


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