Ian threatens western Cuba and much of Florida
Tropical Storm Ian is expected to become a hurricane by Monday morning (9/26/22) and a major hurricane (winds above 110mph) by Tuesday morning. The hurricane is then expected to continue trekking northward over the eastern Gulf of Mexico with a landfall predicted near the Florida Big Bend on Thursday (Fig. 1). At least that is the current thinking from the National Hurricane Center (NHC). It is based on numerous data sets, hurricane hunter observations, satellite data, computer models, solid forecasting skills, and more.
However, NHC is quick to note that when a hurricane moves parallel to a coastline, small changes in the direction of movement can translate into huge changes in storm-related impacts (location and strength of hurricane conditions, rainfall, surge, and more) from what was forecast. NHC forecasters advise not just looking at the positioning of the eye or the “cone of uncertainty,” but rather assess all the information about the storm, especially advice from local officials.
Long-time residents of southwest Florida may remember Charlie in 2004. This hurricane was moving parallel to the coast (albeit much closer than Ian is expected to) and made an unforeseen, sudden shift to the right. Places that were expected to be bypassed by the storm, were suddenly in extremely strong category two to four hurricane winds. This means that people in southwest Florida should recognize that for storms moving parallel to the coast, small changes in track and motion can mean big changes to local areas. These changes can work for people or against them.
The cone width is a function of the average forecast position error of the eye. NHC plots circles at different forecast times and applies a radius representing the distance from the storm center that encompasses two-thirds of the forecast errors. When the edges of these circles are connected, a five-day uncertainty cone is produced.
It is important to recognize that one-third of the forecast errors lie outside this cone. Hence, not being in the cone is no guarantee of immunity from storm impacts. Further, this cone is designed to key on wind risks. Coastal flooding, storm surge, heavy rain, and flooding (river, small stream, canal, lake, and sheet) are not even considered. Similarly, tornadoes can occur, even if the storm has not yet made landfall. In the case of tornadoes, the right side of the storm (looking in the direction of motion) is the most prone for tornadoes to form.
As of 5 p.m. E.D.T. on Sunday (9/25/22), NHC’s track forecast has Ian moving some 200 miles west of the Naples airport on Wednesday. Even if the storm’s wind field expands, Naples, Fort Myers, and surrounding areas should only experience wind gusts of between 40 and 50 miles per hour (again based on current thinking).
However, water is of greatest concern. Ian’s projected path (direction and speed), coupled with southwest Florida’s coastal orientation favors higher than usual tides and significant coastal flooding (i.e., storm surge, plus wave action). Today, is a New Moon, which also favors somewhat higher than usual coastal tidal levels. This lunar positioning will allow for high tides to be at least slightly above average for the next few days.
Inland flooding is a concern, too. Places to the north and east of Naples (in both Lee and Collier Counties) have received more than twice average rainfall for the past 30 days (Fig. 2). Near where I live (north Naples), swales along some roadways have standing water. Lakes in the Vineyards (for example) are already high. Current storm rainfall forecasts are from four to six inches across southwest Florida. As always, local amounts can be significantly greater based on how rainfall banding aligns itself and how storms “train (i.e., a series of heavy showers and thunderstorms move across a location).
I’ll be on WGUF-radio (98.9 FM) in Naples starting at 7:10 a.m. E.D.T. on Monday (9/26/22) to provide additional insights, discuss hurricane and flood safety, talk about preparedness, and address other aspects of hurricanes. Please feel free to tune in and/or call in your questions.
Originally posted 9/25/22
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