Tropical Storm Dorian is moving steadily westward toward the Caribbean.
As of midday Monday, Tropical Storm Dorian was located 135 miles east-southeast of Barbados, and moving west-northwest at 14 mph. Tropical storm conditions are expected to arrive in the Windward Islands Monday evening, and the storm could become a hurricane over the northeast Caribbean by Tuesday evening.
The National Hurricane Center has expressed “higher than usual uncertainty” in recent forecasts for Tropical Storm Dorian. It said the cyclone was challenging to predict due to its compact size. Small storms can sometimes erratically fluctuate in intensity, as they are more likely to be influenced by small changes in their environment.
Forecast data suggests Dorian will navigate through a complex array of factors over the next five to seven days. Most are likely to inhibit development.
First, gradual strengthening is expected by the National Hurricane Center over the next 36 to 48 hours. This is primarily attributed to warm sea surface temperatures and marginally favorable upper level winds over the eastern Caribbean. Pockets of dry air may temporarily delay intensification, but Dorian is still forecast to briefly become a hurricane south of Puerto Rico late Tuesday or early Wednesday.
Wind shear is a term used to describe a changing of wind speed or direction with height. When the shear is high, it can keep a tropical storm from maturing or cause it to dissipate. Higher wind shear is projected by several reliable forecast models ahead of Dorian’s likely path near the Greater Antilles. Timing is critical though, because these areas of stronger winds aloft are also on the move. If Tropical Storm Dorian arrives sooner or later than the projected wind shear, it may have little affect on the storm’s structure or intensity.
Interactions with land are also a major detriment to a tropical cyclone’s development. Multiple obstacles - islands in this case - lie in Dorian’s potential path. The large and mountainous island of Hispaniola, for example, has long been a graveyard for tropical systems. A path directly over the island would likely disrupt the storm’s circulation and result in weakening, or even dissipation. If Tropical Storm Dorian were to move between two islands, or just brush by one of them, the storm would have a better chance of staying in tact.
If Dorian survives the mountainous terrain of the Greater Antilles, the wind shear, and the dry air, it is forecast to be over the Bahamas by the start of the upcoming holiday weekend. Longer-range forecasts keep it to the south of the Palmetto State, but changes are always possible and we will continue to monitor Dorian’s track carefully in the coming days.