“Hurricane” Hal Needham is a storm surge scientist who specializes in data-driven storm surge analysis. He is the founder and president of Marine Weather and Climate.
On September 17, 1947, a Category 4 hurricane struck southeast Florida, generating an 11-foot storm surge at Palm Beach. The seawater at Palm Beach on that date reached the highest recorded level, even topping a 9.8-foot storm tide generated by the “Lake Okeechobee Hurricane” of 1928. Both of these storms generated high enough storm surges to inflict substantial damage along the coast.
Since 1926, five hurricanes have generated coastal floods at least 7 feet high in Palm Beach County. Flooding has reached this level in 1926, 1949 and 1965 and two hurricane exceeded it in 1928 and 1947.
However, all of these events occurred more than 50 years ago. Since then, the area has enjoyed an absence of large storm surges over the past five decades. Why is this?
The absence of large storm surges in this region during recent decades partly has to do with climate and partly has to do with luck, randomness, chance or fortune (pick your favorite term).
Climatologically, hurricane activity in South Florida was suppressed from around 1968-94 due to a negative phase in a climate teleconnection called the Atlantic Multidecadal Oscillation (AMO). Climatic teleconnections are links between weather or pressure patterns and resulting weather phenomena, like hurricanes. El Nino is a familiar teleconnection.
The AMO relates to a temperature index of the sea surface temperature (SST) in the Atlantic Ocean. When the AMO is in a positive (warm) phase, the SSTs are relatively high and hurricane activity generally increases. When the AMO is in a negative (cold) phase, however, SSTs are relatively low and hurricane activity generally decreases. The AMO was negative from around 1968-94, meaning there was less activity in those years, followed by a more active period beginning around 1995.
However, Hurricanes Hugo (1989) and Andrew (1992) were two major hurricanes that struck the Southeast during the AMO cold phase, which proves that these teleconnections relate to general correlation, but do not mean there will be a complete absence of powerful hurricanes.
Randomness also plays a role in hurricane impacts at a particular site, and Palm Beach has been a “lucky” location in recent decades, at least concerning hurricane storm surge.
The 1990s saw Hurricanes Andrew (1992), Erin (1995) and Irene (1999) impact southeast Florida, but none of these storms generated a substantial storm surge in Palm Beach County because of their their tracks and landfall locations. Hurricane Andrew inflicted catastrophic wind and surge damage in Miami-Dade County.
Category 5 winds and a 16.9-foot storm surge tore through areas south of Miami. However, storm surge levels north of Fort Lauderdale were modest and in many cases not even observed. Hurricane Erin made landfall well north of the area, near Cocoa Beach, so the strongest winds in Palm Beach County were blowing offshore. And Irene approached from the southwest, so the water it was pushing mostly impacted the Florida Keys and Everglades.
In the early 2000s, hurricanes continued to strike southeast Florida, inflicting the greatest damage on Palm Beach County in 2004. That September, Hurricanes Frances and Jeanne inflicted substantial wind damage on the county. However, since these storms made landfall near the county’s northern border, the strongest winds in the area were blowing offshore and suppressing surge levels.
Frances produced elevated water levels on the coast, with water levels at Lake Worth Pier reaching 6.3 feet above the NAVD88 datum. Within 10 miles of the Palm Beach-West Palm Beach area, Jeanne produced a maximum surge of around 3.5 feet.
Several more hurricanes followed in 2005, and although storms like Katrina and Wilma generated substantial wind and rain, their track and intensity were not ideal for generating high storm surge near Palm Beach.
This lack of large surges over more than five decades may leave many residents of Palm Beach County unprepared for saltwater inundations in the future.
Massive population growth in this region will substantially increase storm surge impacts even if future storm surges do not surpass the frequency or magnitude of surges in the past. From 1970 to 2014, Palm Beach County has grown by more than 400 percent, as the population increased from approximately 349,000 to 1,398,000. That’s an addition of more than 1 million people in just 45 years.
Sea level rise is also an issue for the region (and the world for that matter), meaning a lower magnitude storm surge today could reach the same water levels reached in the 1960s because the seawater has a head start. People along Florida’s Atlantic coast may feel that sea level rise is an issue restricted to Miami-Dade and Broward counties and will not affect Palm Beach County and points north. That’s not the case, though.
Long story short, Palm Beach County is vulnerable to inundation from coastal flooding, but because of climatological factors and a bit of good luck, the area has avoided any substantial storm surges for more than 50 years. Many local residents are transplants who have never experienced a hurricane before, and long-timers likely think of hurricanes as wind events instead of storm surge events, given the history of the past five decades. We can only hope residents realize their luck will run out and saltwater will once again inundate their coastal communities so that they’re prepared for the consequences.