As I type this Thursday night (7 September), Hurricane Irma is motoring along between Hispaniola and the Turks and Caicos Islands, on an increasingly probable Sunday rendezvous with at least South Florida and the Upper Keys. This map, edited for space considerations, is for the historical record, frozen in time, at the time I write (see the National Hurricane Center for the most current information!!!):

If this forecast track verifies (and there still is uncertainty involved, as per the width of the cone!), then South Florida would see the most destruction at least since Hurricane Andrew, and probably much more. For those of us who were inside Andrew (see my lengthy retrospective here for more), it’s hard to imagine how it could be worse, but it can.

Yes, Irma could be (it’s too soon to use “will be” as some media headlines already tout) much more dangerous and destructive to more of South Florida and Keys than Andrew. This dire scenario is realistically plausible for four principal reasons:

PATH/INTENSITY COMBINATION: When one examines historical tracks of South Florida or even specifically Dade County and middle-upper Keys hurricanes, readily one sees that category-5 Andrew was the anomaly, with its perpendicular, fast-moving westward path. The paths of major hurricanes Donna, Miami-1926, and Lake Okeechobee (1928, which made landfall near Palm Beach), among others, followed a more common and potentially destructive (to today’s South Florida) track from the south-southeast or southeast. Even when I was at NHC, an increasingly long time ago, a more southerly track and category 4 or 5 intensity combination with the area on the near-right side of the center — almost exactly that currently forecast by NHC for Irma! — was hailed as the worst-case scenario for the South Florida megalopolis. This track would wreck a long swath of my beloved Florida Keys too. That time may be almost upon us. Let’s hope otherwise while preparing for this most-extreme possibility.

INEXPERIENCED FRAMES of REFERENCE: Most people now in South Florida and the Keys weren’t there for Andrew. The bulk of those who were did not experience the real Andrew in person; they were north of the devastated zone — or in the Keys, south of it, with little direct effect. There is a relatively mobile, young populace with a lot of turnover — more of it not speaking English as a first language than in most other metro areas nationwide. Anybody can learn facts; however, true understanding also includes direct, first-hand experience, which most folks in South Florida do not have. I hope they pay attention to those who do and prepare well!

EXPOSED POPULATION: Andrew did not substantially impact most of South Florida. Only Dade County (since renamed Miami-Dade) south of the latitude of Coral Gables experienced widespread damage, with a few hundred thousand residents in the most-damaged areas south of Kendall Drive (SW 88th St.) to Homestead and Florida City. Andrew then quickly swept across the Everglades and out to the Gulf. Though the storm surge peaked at almost 17 feet, it did so in a small and mostly uninhabited area, and largely was stopped from going very far inland due to damming by mangroves and debris. Such is not the case in this setting, with damaging storm surges possible up a long swath of developed, exposed shoreline largely unshielded by mangroves. Now, with Irma’s worst side potentially roaring right up the Interstate-95 corridor in South Florida, over six million people occupy a similar relative position of this forecast track even inland, in the prospective wind-damage swath. If even the same percentage of people don’t prepare well and/or experience misfortune as in Andrew, a far higher number would die, suffer injury, and experience unsafe and unsanitary conditions in the aftermath, and probably with longer power outages…

INFRASTRUCTURAL LOGISTICS: A lengthwise path up the metro corridor maximizes destruction potential. Simply put, more targets means more damage! Even with some of the best building codes in the nation, Andrew showed us that codes aren’t necessarily followed. Even with mostly well-built structures, damage still happens with gusts potentially in the 125-180 mph range. Think Andrew’s swath area, in multiples of ten — yes, plural “multiples”. Though Andrew had its notable resource-mobilization problems (remember Kate Hale’s infamous, “Where the hell is the cavalry…?” plea?), and presumably lessons were learned at all levels from that on through Katrina, Wilma, Matthew and other storms there, this kind of path is the worst logistically. If it happens as currently forecast, the entire South Florida strip from Homestead to north of Palm Beach is vulnerable to destructive winds, near-coastal storm surge, flooding rains, and maybe even tornadoes in the outer bands before Irma’s core region arrives. [See my scientific review article on the tornado threat with hurricanes, if you aren’t yet familiar with it.] This would be much akin to running a lawn mower along the full length of that overgrown strip of grass by your curb, instead of quickly across it. In the storm’s wake, with a far larger swath of populated area devastated, first-response, massive debris cleanup, sustained humanitarian relief, environmental-hazard mitigations, and power-restoration efforts all would be much more difficult and time-consuming, with a risk of more suffering and death per square mile, over many more square miles than Andrew, before the “cavalry” in all its forms can arrive.

If that track bears out, we would witness the greatest amount of single-storm damage ever inflicted upon this nation. Because of forecast uncertainty regarding timing and angularity of the likely northward turn, it is too soon to use the unqualified verb “will”, however. That confidence won’t exist until several hours beforehand. Still, all must prepare for the worst, while hoping and praying for the best. Even a little over two days out, it’s already too late for many of the unprepared to evacuate, shutter up, or stock supplies. The best that can happen is for Irma to make that turn unexpectedly soon, along 80W longitude or sooner, and go up the Gulf Stream. [Even then, it would mean awful developments somewhere in the Carolinas, lest we forget areas downstream.] That best-case scenario is looking less probable with time. A delay, with a turn up the lower/middle Keys and west coast, would be less devastating for the South Florida I-95 corridor, but would visit horrible havoc on smaller communities in the Glades and perhaps the coastal corridor from Chokoloskee and Marco to Naples and Fort Myers — an area of which I also have grown quite fond.

Please do not forget rural folks and the agricultural impact of Irma also. For crops, this also represents a worst-case hurricane scenario, as most of the Florida Peninsula would be affected by destructive winds and flooding rains. Fruit crops, berries, vegetables, tropical plants, sugar cane, and livestock all would suffer massive losses with a large hurricane barrelling right up the peninsula. You and I would see the impacts at the grocery-store checkout counter, and local farmers (as with many in southern Dade County after Andrew) could be bankrupted.

As of this writing, a small subset of NHC forecasters is in Tampa, having been moved there on a special small-plane flight out of Opa-Locka Airport to catch commercial flights to Washington, DC, tomorrow morning. They will staff ready-set-go workstations at the Weather Prediction Center in College Park, MD, and issue hurricane forecasts from there in the event the NHC facility is too disabled. Unlike in 1992, NHC and the Miami NWS office are in a reinforced concrete facility well inland, specifically engineered against this very contingency, and shuttered with metal already tonight.

NHC did similar backup procedures for Andrew as well; fortunately and somewhat miraculously, most systems stayed online despite the lack of air conditioning (not enough generator power for that and the computers), and the generators worked as designed until commercial power was restored within a couple days. The backup forecasters from NHC came home a few days later, having not been needed, though one whose car was parked at the center’s then-location in Coral Gables found it in an awkward position. Because Andrew’s effects largely were from there southward, north-south power restoration happened fairly quickly. This time, with the potential for a long-axis path of damage up the I-95 corridor, such geographic fortune would not be available, and as noted above, restoration of commercial power for much of South Florida may be a much-longer process.

That’s enough for now. Again, see the National Hurricane Center for the most current information, watches and warnings on Irma. They are the sole official authority on hurricane forecasting and the center of world expertise in predicting these storms.

God be with the people of South Florida and the Keys as they face their greatest threat of modern times.