Despite the record-breaking landfall drought, hurricane history has shown time and again that the U.S. is very much at risk from these monsters of the weather world.
During hurricane season, all of the coastal Atlantic regions are in play to some extent. But are there areas more favored than others to see a hurricane. And with more than 160 years of hurricane data to sift through, there are plenty of tales to be told and clues to unearth.
Looking back through all of the hurricanes on record since 1851, we can plot the areas that are historically most at-risk for hurricanes, from the modestly weak to the monstrously intense.
This is hurricane country
Hurricane season is often referred to as “tropics season,” the tropics being roughly defined in the Atlantic as the area from the equator to north to 23 degrees latitude. The region does not include any of the continental United States, ending just south of Florida. It does cover the main development region to the west of Africa, and then across the Caribbean as well as Central America into South America.
But the tropics is not where all storms form and mature. A majority of the hurricane activity occurs to the north of the tropics, in either the subtropic or temperate zones across the North Atlantic. This happens partly because a lot of storms tend to bend north as they become stronger. And in many cases, continental low pressure systems and their ventilation-supporting upper level troughs can temporarily help a hurricane develop as it picks it up and sends it out to sea.
Another dominant hurricane passageway can be seen from the western Caribbean up into the Gulf of Mexico. But even here, a place we generally think of as a breeding ground for behemoth storms, the total cumulative numbers are lower than the region off the East Coast, and the Mid-Atlantic in particular.
That rogue track across Central America and into the eastern Pacific Ocean included Hurricane Irene of 1971, which later became major hurricane Olivia on the other side of Mexico. Irene was one of only a handful of storms to make that hop across land, but was the strongest storm to redevelop on the other side.
Where the majors live
For hurricanes, the track up the East Coast is something of a death march. As a hurricane gets further north it typically encounters cooler water and a more disruptive atmosphere. Although there is often strengthening off the East Coast as storms cross the warm Gulf Current, it is often temporary
The real hurricane beasts — those rated Category 3 or stronger with winds of at least 111 mph — have tended to live in a smaller zone, based on history. We call these major hurricanes, in no small part because they are a major problem for whoever is in their path.
Looking at the map above, it’s easy to see why meteorologists fear a track to the north of the Greater Antilles — Puerto Rico, Hispaniola and Cuba — and into the Bahamas. That’s a prime track for historic hurricanes (think Andrew in 1992, or Katrina in 2005) many of which have later tracked across southern Florida. Another favored region for major hurricanes extends from the Caribbean Sea north into the Gulf of Mexico.
Violent hurricanes tend to favor the tropics
The stomping grounds of the strongest hurricanes shrinks even farther to the south. The most intense storms — those rated Category 4 and 5 — are thankfully few and far between, but they still target a lot of highly-populated real estate.
For Category 4s, with wind speeds of at least 130 mph, we again see a clear path just north of the Greater Antilles and toward the Bahamas and southern Florida. In fact, the Miami region is among the most likely to see such storms. Something we can keep in mind when recalling that it has now been almost 10 years since the last major hurricane hit that region, or anywhere in the United States for that matter.
The Category 5 only map — not embedded because there are not many data points — keeps with the southern focus as strength increases. And we generally see that while a majority of Atlantic hurricane conditions occur outside the tropics, the biggest and baddest hurricanes are those in and near the tropics.
Two main factors are bath-warm water which fuels the storms, and less influence from mid-latitude low pressure systems that inflict detrimental winds on tropical systems. Of course, in a year like 2015, the hot zone is pretty much shut down by atypically strong wind shear that blows systems apart.
It’s a delicate balance, as with most weather.
Noted briefly up front, only segments of storms at hurricane force were used in this analysis. The parts of each storm path with wind speeds of 73 mph or less (tropical depression or tropical storm) were ignored.
This was done to highlight just the region where hurricane conditions likely occurred, rather than the whole path which is often made up of lengthy periods of sub-hurricane conditions.
I went about this analysis using 1-degree grids for several reasons, chiefly the following:
In the main zone of activity it is roughly consistent to the average or median radius of maximum winds of a hurricane times two. In other words, a hurricane can hit one of the 1-degree grids in the middle and it’s worst winds could fit or mostly fit within the box. This isn’t always the case, and there’s no real way to capture the extent of the maximum winds perfectly in methods such as these for multiple reasons. It still gives a considerably better idea than a simple line that only tracks the eye.
1-degree grids are also nicely referenced by boundaries we are all well quite aware of in the latitude and longitude grid of Earth. Smaller scale grids tend to highlight just the tracks, while larger grids lose significant detail as size increases.
These maps should by no means be used to say that hurricanes won’t occur outside the regions shown. Just this year, in a relatively tame season, we’ve seen a storm called Fred defy boundaries by forming outside the zones identified by history.
That said, the zones of concentration will likely yield the most results going forward. History can be one of the best forecasting aids out there if used wisely.
I skipped embedding category 2+ here, but here’s that map if you’re interested. Perhaps the main difference from category 1+ to category 3+ is that the zone shrinks south and southwest, and the more numerous of each tend to continually favor further south. A trend that continues as intensity steps up further.