Unfortunately the latest update from the National Hurricane Center shows another slight shift westward putting the South and Central West Coast of Florida in the path of immediate concern. –ADVISORY UPDATE HERE–
If you’ve followed along you might have noticed the ‘worst case scenario’ for the West coast of Florida. –Outlined Here– However, I want to draw your attention to the forecast timing; because there’s a remarkable synergy lining up with Hurricane Donna from 1960. First here’s the latest NHC forecast map and times:
Timing is critical here. Between the two “M”‘s [Max Winds] (2pm Sun, and 2am Mon) you might note the geography of the coastal community, shows an inlet. That inlet is the mouth of the Caloosahatchee River. Also known as Punta Rassa.
During 1960 Hurricane Donna the Caloosahatchee River dropped significantly as a result of the powerful Westerly winds from approaching Donna and the local tide. It looks like the exact same thing might happen again:
The maximum Westerly winds (top of the counterclockwise Irma) are forecast to happen during the outgoing tide. Sunday: High Tide 5:09pm -then- Low Tide at 10:08pm (link) The current forecast timing of the top of Irma, pushing water out to the Gulf of Mexico, coincides with the outgoing river flow.
However, the important part –we continue mentioning– is the backside of the storm where the winds blow in from the West and bring the storm surge.
Unlike Hurricane Irma, in 1960 Hurricane Donna was traveling North East (she made a long loop), and the backside of the storm provided only a tidal rise of 4 to 7 foot storm surge to the Fort Myers/Estero area. That was indeed damaging though SWFL area was sparsely populated.
WIKI – Early on September 10, Donna made landfall near Marathon, Florida with winds of 130 mph (215 km/h), hours before another landfall south of Naples at the same intensity. Florida bore the brunt of Hurricane Donna. In the Florida Keys, coastal flooding severely damaged 75% of buildings, destroyed several subdivisions in Marathon. On the mainland, 5,200 houses were damaged, which does not include the 75% of homes damaged at Fort Myers Beach; 50% of buildings were also destroyed in the city of Everglades.
Hurricane Irma is forecast to take a more Northerly (directly along the coastline) path. Which predictably will bring a much stronger backside storm surge. Unfortunately, that inbound Gulf of Mexico water coincides with the natural inbound tide.
Monday September 11th: High Tide 04:31 am -then- Low Tide at 11:35am (link).
In the time between the Low Tide Sunday at 10:08 pm, and the High Tide Monday at 04:31 am, the strongest of the East bound (on shore) winds are expected.
♦Irma is far more powerful than Donna was in 1960. Irma is also far larger than Donna was in 1960. ♦Irma is forecast to follow a much more damaging path along the coast than Donna was in 1960. ♦Donna brought a 7′ storm surge, Irma could dwarf that. ♦The coastal area is much more densely populated than when Donna hit in 1960. ♦The Gulf Side coastal shallow water is more prone to movement by wind force.
What does all this mean?
Well, information is how we make prudent decisions. If you overlay the National Hurricane Center timeline with the local tidal charts for the impacted communities; you see the potential worst case scenario for storm surge that could dwarf all prior forecasts of the worst case scenario. These Maps could be under-stating the risk; they most certainly are not over-stating it.
I’m not trying to alarm anyone, but if you are near the coast -anywhere near the coast- from Ten Thousand Islands up to Tampa and St. Pete; especially in Charlotte Harbor or along the Caloosahatchee river basin; or if you are even in a moderate non-evacuated flood zone; if you live West of U.S. 41; and if you are wondering whether you should seek shelter on higher ground today…. JUST DO IT !
We have seen hurricanes carve up barrier Islands, remove and build others, and swamp coastal communities with storm surge. We have never seen a recorded major hurricane track from South to North on, or near, the West coast of Florida.
The west coast tides and the arrival of the Atlantic region’s most powerful hurricane are in alignment for a worst case scenario for flooding and storm surge. There is still time today to take shelter from that storm surge, and for those North of Boca Grande (North of Lake Okeechobee – 28° latitude) there’s still time to evacuate.