Shell Mound wrote:This thread is somewhat in the mould of the past what-ifs involving
hypothetical hurricanes. As in the latter example, hypotheticals are based on historical precedent. The problem is that historical precedent is not long enough to determine what is or isn't possible. One cannot conclude that the northern Gulf
cannot, as a rule, support intensifying major hurricanes. The climate of the region has changed over long periods of time, and what applies today may not have applied in the past, or may not apply to future cases. When discussing worst-case scenarios or storms that
"might have been" worse, there are many factors to consider, such as demographics, population, settlement patterns, geography, geology, and topography, besides a storm's angle of approach, size, fetch, intensity, speed, rainfall, and a number of synoptic and mesoscale factors that come into play. Theoretically, almost every storm, even the worst on record, could have been even more catastrophic had one or more variables been different.
However, I wouldn't consider Wilma to have been "worse than expected," given that
advisories between
0300Z/18 October and
0300Z/24 October consistently called for at least a low-end Category-2 hurricane to strike Southwest Florida; forecasts were consistently in the 85-to-100-knot range at the projected time of landfall in Florida. The actual landfall intensity, 105 knots/950 mb, was not far off from the range of possibilities. The miscommunications in Southeast Florida resulted from local TV meteorologists' wording, not the Hurricane Center's, according to my recollections. Anyway, I personally doubt that Wilma could have hit South Florida as a Category-4 or stronger cyclone, given the strength of the shear over the Gulf of Mexico. Wilma was able to intensify because it left the Yucatán Peninsula as a weaker, Category-2 system, instead of passing through the Yucatán Channel as a Category 4+. Thus, Wilma was more like Eloise 1975 than Katrina 2005 as it entered hostile conditions near the shelf waters. Weaker systems, Category 1 or 2, tend to benefit from baroclinic forcing more than storms that are already extremely intense (Category 4+).
Based on past discussions on this forum, some of the worst-case scenarios are as follows:
- A Category-5 cyclone of similar intensity to Irma, possibly annular or quasi-annular—à la Isabel 2003—that strikes the USVI and just south of San Juan, PR, placing that city in the powerful northeast quadrant, and then passes north of the Greater Antilles, taking a path over the deeper channels of the southeastern Bahamas, en route to a landfall on Nassau, New Providence Island, as a Category 4+, then continuing northwestward, its northern eyewall affecting Freeport, before making landfall on Sebastian, FL, as a Category 4+, and continuing north-northwestward to just west of Jacksonville, its eyewall affecting downtown and the St. Johns estuary. The system slows as it nears the latitude of Jacksonville and eventually stalls over or just west of Savannah, GA, producing a prolonged fetch over coastal SC and GA, including the Charleston area.
- Similar to the above, but continues west-northwestward after PR, taking a path similar to Irma's through the southeastern Bahamas, then assuming a more northerly trajectory to strike Andros Island, continuing over the Gulf Stream to hit just south of downtown Miami, FL, as a Category 5, similar to Andrew in strength but mimicking Irma's size, with the eyewall affecting downtown Miami and Fort Lauderdale. The storm then heads northwestward to Egmont Key, near the mouth of Tampa Bay, its northern eyewall affecting downtown St. Petersburg and/or Tampa, then gradually curves over the northeastern Gulf of Mexico, hitting west of St. Marks, its northeast eyewall affecting downtown Tallahassee.
- Similar to the first scenario, but instead of hitting FL, the cyclone curves northeastward post-Nassau, passing well to the southeast of Cape Hatteras, but then interacts with a negatively tilted mid-level trough and accelerates north-northwestward, making landfall over the southern tip of Barnegat Bay, NJ, as a large Category-3 cyclone, similar in intensity to the 1938 New England hurricane, comparable in size to the 1944 Great Atlantic hurricane, Floyd 1999, and Sandy 2012. The eye moves north-northwest after landfall, too, passing over Newark, with the eastern eyewall affecting the lower Hudson River, Manhattan, and western Long Island. Once past New York City, the system slows dramatically, transitioning into an extratropical cyclone that merges with a cold front, producing torrential rains over portions of New York State and New England. As in 1938, this scenario follows a very wet summer in portions of the Mid-Atlantic and Northeast, and coincides with astronomical high tide.
Given property values and infrastructure, the absolute worst-case scenario, blending size, intensity, fetch, angle of approach, and storm surge, would involve the USVI, San Juan, Nassau, the east coast of FL (Miami-Fort Lauderdale, Kennedy Space Center, Jacksonville), Savannah, Charleston, Chesapeake/Delaware Bays, and of course Newark, NYC, Long Island, and southern New England. Probably no single storm would hit all of the points I've highlighted, but anything of the above that would involve these places could be far, far costlier and deadlier than a similar impact to New Orleans or Houston-Galveston. There are simply more financial and other resources at stake.
So, yes, I'm thinking a blend of Irma, Maria (in PR, St. Croix, and Dominica), Floyd, Andrew, Katrina, 1926 Miami, 1928 San Felipe II, 1938 New England, 1944 Great Atlantic, and Sandy all rolled into one. Perhaps a Donna-type track over the eastern U.S., melded with an Irma-esque track through the islands (with more impacts to San Juan and Nassau), would do the trick, and potentially bring Tampa/St. Petersburg into the high-risk zone as far as surge is concerned, too.
