Most of July and August have been relatively quiet with few tropical waves forming in the Gulf of Mexico and the Atlantic. We are now entering the peak of Atlantic Hurricane Season where we generally see tropical systems begin to form more frequently. A tropical wave formed in the tropical North Atlantic basin just a few days ago and quickly became more organized over the past few days as it approached the Lesser Antilles. Utilizing the warm sea surface temperatures (SSTs) and minimal atmospheric wind shear in the area, Tropical Storm Dorian formed and impacted the Lesser Antilles before entering briefly into the Caribbean Sea while moving steadily north-northwest towards Puerto Rico and the Dominican Republic.
Due to Dorian’s change in direction, it is currently now impacting the small island of Puerto Rico and parts of the U.S and British Virgin Islands. As of the 2:00 PM AST advisory from the National Hurricane Center, Dorian is now a Category 1 hurricane on the Saffir-Simpson Hurricane Wind Scale with wind speeds of 80 mph. Dorian is now the second hurricane of the 2019 Atlantic Hurricane Season.
Dorian is currently passing the Lesser Antilles and heading northward into the open Atlantic, an area that could strengthen this system further as it continues to track in the direction of Florida over the next several days.
August through October is generally the time when tropical cyclones are more likely to form and when we typically see an increase in the frequency of major hurricanes in the North Atlantic. Dorian could become the first major hurricane of the 2019 Atlantic Hurricane Season.
At this time Hurricane and Tropical Storm Watches and Warnings continue for Puerto Rico and the U.S. and British Virgin Islands. The main threat will be flash flooding and landslides across the islands which are still recovering from Category 5 Hurricane Maria (2017) which brought widespread destruction particularly to the island of Puerto Rico.
Now that Dorian is entering into the open Atlantic it will have plenty of time to strengthen before turning more westward towards the Bahamas and Florida. At this time the National Hurricane Center is forecasting Dorian to be a major hurricane (Category 3-5) by the time it moves close to the Bahamas. Current forecasts have it at Category 3 strength on the Saffir-Simpson Hurricane Wind Scale as it approaches the shores of Florida but we cannot rule out the possibility of this storm increasing in strength, especially with the atmospheric and ocean environment being favorable for development.
SSTs are prime for further strengthening with water temperatures between 84 and 89°F. Tropical cyclones need SSTs of at least 80°F in order to strengthen and continue to develop. Dorian is currently over these prime water temperatures and this will aid in strengthening the system further in the coming days.
Also, helping to air Hurricane Dorian is the minimal amounts of wind shear in the atmosphere. A tropical cyclone needs areas with light upper level winds in order to grow and strengthen. If the wind shear levels are high (shown in red above) these will help to tear the storm apart. Dorian is currently in a favorable area for tropical development and will likely continue to be in prime conditions as it continues west-northwest.
If there is any hope to this storm weakening it would be located just to the north of Hispaniola where a small area of intense wind shear is located. This could aid in weakening Dorian just slightly as it continues towards the United States. However, wind shear values are expected to remain minimal across the the tropical Atlantic and this could become a deadly scenario as we approach Labor Day weekend.
It is a very real possibility that Florida will be dealing with another major hurricane in the next several days. This will make it 4 years in a row that the state has experienced a major hurricane. Hurricane Matthew (2016) broke the decade long “major hurricane drought” for Florida when it moved up the east coast of Florida. A year later Hurricane Irma (2017), impacted the Florida Keys and parts of South Florida as a major Category 4 hurricane. Finally, just last year, Category 5 Hurricane Michael (2018) brought widespread destruction to the panhandle of Florida.
Most models are in agreement that Dorian will impact the state of Florida with the majority indicating central parts receiving a direct impact. However, with Dorian growing in size and strength this will not be an isolated event. Dorian’s forward motion to the west will push sea water far inland and spread up the coast of Florida. Widespread heavy rainfall will be possible across the state of Florida. If there is any good news with Dorian, it is that it is moving steadily at a speed of 14 mph. What we do not want is a slow moving storm, like what we have seen with Hurricane Florence (2018) and Hurricane Harvey (2017), both of which stalled out over land and delivered record amounts of rain and flooding to the Carolinas and Texas, respectively.
Florida Governor Ron DeSantis has declared a state of emergency for the state in preparation for Hurricane Dorian’s arrival.
Sunday night into Monday morning is expected to be when Dorian will potentially make landfall along the east coast of Florida.
A direct hit by a major hurricane along the east coast could cause significant storm surge flooding, especially for areas that will go through the powerful northeast quadrant of the storm, which usually contains the highest storm surge and powerful winds found in a hurricane.