Hurricane Dorian has been a tricky forecast and an unusual storm from the start — both because of its small size and the surrounding weather systems that will determine its fate. Typically, a storm located in its position of more than 200 miles northwest of Puerto Rico on Thursday afternoon would not make landfall on the Florida coast.
We can look to past storms for guidance on how Dorian may — or may not — behave. Historical analogues have their limits, however, as each storm is governed by its own set of circumstances.
As of 11 a.m. Thursday, Dorian was swirling over 21.4 degrees north latitude, 67.2 degrees west longitude. Since 1947, a NOAA database shows that 30 hurricanes have passed within 100 miles of this location over the open ocean, including the previous iteration of Dorian in late July 2013. (The National Hurricane Center recycles names every six years unless a storm causes enough damage/casualties to prompt the name’s retirement.)
Of these storms, only five have made landfall in Florida, two of which passed directly over the Florida Keys. Two hit the eastern coast of Florida. Among them was Frances in 2004, which battered Port St. Lucie as a Category 2 storm.
“While Frances’s track to date isn’t a good analog for Dorian, its future track isn’t a horrible analog,” wrote Philip Klotzbach, an atmospheric scientist at Colorado State University. “[Dorian] looks like it will slow up as it heads toward land, too … just like Frances did in 2004.”
There were others, too. An unnamed storm in 1947 plowed ashore with Category 4 winds in Fort Lauderdale. One additional storm — Kate, in 1985 — danced over Cuba before recurving north in the Gulf of Mexico and coming ashore near Panama City.
“The majority of them recurved before reaching the United States,” explains Brian McNoldy, Capital Weather Gang’s tropical weather expert. “The notable examples of ones that didn’t recurve include Irma” in 2017.
So all told, two out of the 30 storms made landfall on the eastern coast of Florida. Ten of the 30 made landfall in the United States as at least a tropical storm.
We can also work backward to see where storms affecting Florida generally come from. Those that move ashore along the eastern coast of Florida generally move in from the south or southeast. We looked at 128 systems that have passed near or directly over Florida’s eastern coast since the 1800s. About 11 of those passed within 100 miles of Dorian’s Thursday morning position, about 8.5 percent. In other words, the forecast path of Dorian is unusual but has precedent.
One of the more bizarre elements of Dorian’s predicted path is the broad left curve it will probably make between Friday and the weekend. When tropical cyclones drift north, they ordinarily recurve to the right once they’re swept up by mid-latitude weather systems.
What’s spurring Dorian’s unusual jaunt? The Bermuda High. It’s a ridge of high pressure that parks over the Atlantic this time of year, dominating large-scale steering currents and acting as an atmospheric guardrail that will guide Dorian along.
If the system is weaker or farther east, Dorian could escape out to sea. But if it’s stronger — as forecast right now — then the storm could be suppressed, prevented from meandering north, and instead could plow into Florida.
This curvy path also allows Dorian to circumnavigate most, if not all, of the Bahama islands, keeping its core over the warm waters of the tropical Atlantic. This would allow it to intensify significantly. The National Hurricane Center is forecasting Dorian to be a Category 4 storm or greater at landfall sometime Monday into Tuesday along the eastern shores of the Sunshine State.
Of the roughly 18 or so major (Category 3+) hurricanes to make landfall on Florida’s eastern coast that were available in the database, only one came ashore on the northern half of Florida’s Atlantic coast. Nearly all the others — 16, in fact — hit south of Port St. Lucie.
What’s this all mean? If weather models and the National Hurricane Center are correct in their forecast of a major hurricane making landfall on Florida’s eastern coast, then Dorian could be in rare company. This is especially true if the storm makes landfall north of the Space Coast. However, there’s a remote chance of Dorian’s center remaining offshore entirely, just skimming the coast before being swept north.