Dorian looks set to pass over the northern Bahamas in the coming days as
potentially a Category 5 major hurricane, but forecasts regarding future U.S.
impacts remain significantly uncertain, with the latest guidance providing a
twist in the tale that no one anticipated a few days ago.
Understanding the Uncertainty: A Matter of Timing
The meteorological situation that Hurricane Dorian finds itself in is as fascinating as it is uncertain. Several days ago, Florida was bracing itself for potentially its third major hurricane landfall in as many years. Now, Dorian looks more likely to make landfall in the Carolinas, or, as some models increasingly suggest, it may recurve soon enough that is misses the U.S. entirely. So, why have the forecasts been so uncertain? It’s all to do with timing.
Co-authors: Michael Kozar, Senior Modeler, RMS HWind; James Cosgrove, Senior Analyst, RMS Event Response
Michael underwent rapid intensification in the two days leading up to landfall, reaching the Florida Panhandle coastline as a strong Category 4 major hurricane with maximum sustained wind speeds of 154 miles per hour (247 kilometers per hour), according to the RMS HWind real time service. At landfall, Michael had a tight inner core and its strongest winds were located just 14 miles (22 kilometers) south-southeast of the center of the storm near Mexico Beach. Tropical storm force winds extended up to 115 miles (185 kilometers) eastward along the Panhandle coastline to Pensacola.
Whilst the Saffir-Simpson Hurricane Wind Scale (SSHWS) is exclusively based on maximum sustained wind speeds, which often only covers a very small part of the system, the Integrated Kinetic Energy (IKE) metric conveys the intensity, size, and structure of the storm’s wind field into one number and has become a useful metric for comparing the destructiveness of storms. Using the IKE metric, we can compare and contrast Hurricane Michael to other events in the RMS HWind historic archive.
From first light yesterday (October 11), the full extent of the damage from Major Hurricane Michael across the Florida Panhandle and the wider region became clear — and it really was as catastrophic as we all had feared.
Although Major Hurricane Michael could be regarded as a more traditional “wind and surge” event compared to recent flood events of hurricanes Harvey and Florence, this was not just a coastal event. The trail of destruction extends far from the landfall location near Mexico Beach (pop. ~1,000) and neighboring Panama City (pop. ~36,000) and well into the state of Georgia. Whether it is from the destruction of homes in the towns near landfall, or the widespread power outages, felled trees, damaged roofs, and debris, the clean-up operation is going to be a long process. And tragically, as of Friday, October 12, eight fatalities have been confirmed, including four in Florida, one in Georgia, and one in North Carolina.
After the flood-driven impacts of Category 1 Hurricane Florence just under a month ago, yesterday’s unfolding drama from Major Hurricane Michael was dominated by damaging winds that were within touching distance of a Category 5 storm.
Major Hurricane Michael made landfall near Mexico Beach, Florida, at 17:15 UTC (12:15 CST) on Wednesday, October 10, as a Category 4 major hurricane — the first Category 4 or stronger hurricane to make landfall in the Florida Panhandle on record. At landfall, its maximum sustained wind speed was 155 miles per hour (250 kilometers per hour), just two miles per hour short of Category 5 classification.
Michael’s intensity at landfall has set numerous records. It becomes the strongest hurricane (by wind speed) to make landfall in the continental U.S. since Andrew in 1992 and the strongest (by wind speed) October landfilling hurricane in the continental U.S. on record. Its minimum central pressure of 919 millibars makes it the most intense hurricane (by minimum central pressure) to make landfall in the U.S. since Camille in 1969.
Michael had undergone rapid intensification of 35 knots and 46 millibars in the 24 hours up to landfall, benefiting from ideal development conditions — minimal wind shear and a warmer-than-usual Gulf of Mexico with sea surface temperatures one to two degrees Celsius above average. Its intensification was relentless right up to landfall and resulted in catastrophic damage in portions of coastline along Florida Panhandle.
Prior to landfall, more than half a million people were under evacuation orders, and more than 20 million people in five states were under either a hurricane or tropical storm warnings.
In its short life, Hurricane Michael has certainly developed quickly — it only achieved tropical storm status just four days ago on Sunday, October 7. And now, according to the latest bulletin from the National Hurricane Center (NHC), as at 12:00 UTC today, Michael has strengthened further, into an extremely dangerous Category 4 major hurricane, with maximum sustained wind speeds of 145 miles per hour (233 kilometers per hour).
The 09:00 UTC NHC bulletin placed Michael at about 140 miles (225 kilometers) south-southwest of Panama City, Florida, tracking north at 13 miles per hour (20 kilometers per hour). Hurricane-force winds currently extend outward up to 45 miles (75 kilometers) from the center and tropical-storm-force winds extend outward up to 185 miles (295 kilometers). According to the latest RMS HWind Forecast Storm Track Probabilities and Deterministic Scenarios chart (pictured below), Panama City has a 95 percent probability of the center of Michael passing within 50 miles.
It’s hard to believe that Hurricane Michael, the thirteenth named storm of the 2018 North Atlantic hurricane season, only achieved tropical storm status just two days ago on Sunday, October 7. Tracked by the National Hurricane Center (NHC) since October 2, Michael started out as a broad area of low pressure over the southwestern Caribbean Sea, a couple hundred miles north of Panama.
Becoming more organized as it began to move toward the Yucatán Peninsula, by October 6 it achieved Potential Tropical Cyclone status. Between October 7 and October 8, rapid intensification saw sustained wind speeds jump from 35 miles per hour to 75 miles per hour (120 kilometers per hour) by midday local time on October 8. Skirting between the eastern tip of the Yucatán Peninsula, and the western tip of Cuba, Michael entered the Gulf of Mexico late evening local time on Monday, October 8.
As of 09:00 UTC today (Tuesday 9), the latest NHC advisory located Michael at about 420 miles (680 kilometers) south of Panama City, Florida and about 390 miles (630 kilometers) south of Apalachicola, Florida, with sustained winds at 90 miles per hour (150 kilometers per hour), placing it as a Category 1 hurricane on the Saffir-Simpson Hurricane Wind Scale (SSHWS). Michael is moving toward the north-northwest at close to 12 miles per hour (19 kilometers per hour). Hurricane-force winds extended outward up to 40 miles (65 kilometers) from the center and tropical-storm-force winds extended outward up to 195 miles (315 kilometers).