Add two hurricanes and 14 tropical storms to the official historical record of Atlantic cyclones.
That’s how many meteorologists “discovered” when they looked back at the 1966-1970 hurricane seasons through today’s techno-scientific lens.
The latest findings are part of a massive ongoing project to reassess the U.S. Hurricane Center’s storm database at the National Oceanic and Atmospheric Administration, using modern methods to make it more accurate. Work began in the 1990s. With some exceptions, the research has moved chronologically, at five-year intervals, and findings are published as each time period is completed.
The report for 1966 through 1970 was recently released and can be found on the NOAA website: https://www.noaa.gov/data/#hurdat.
The two additional hurricanes are the result of researchers upgrading the intensity of two previously known storms. Both occurred in 1970. One had previously been listed in the database as a tropical depression, meaning it had sustained surface winds of less than 38 mph. The other had been considered a tropical storm, with sustained winds of between 39 and 73 mph. A hurricane has sustained winds of at least 74 mph.
In addition to reclassifying those two storms as hurricanes and registering an additional 14 tropical storms, the researchers corrected the record concerning the strength of several hurricanes, downgrading some and upgrading others. On the Saffir-Simpson Scale, there are five categories:
• Category 1: 74-95 mph
• Category 2: 96-110 mph
• Category 3: 111-129 mph
• Category 4: 130-156 mph
• Category 5: 157 mph and above
Christopher Landsea, chief of the National Hurricane Center’s Tropical Analysis and Forecast Branch, and the man in charge of the Hurricane Re-analysis Project, told the Source that it was satellite imagery that convinced his team to upgrade the two 1970 storms to hurricane status.
Another change to the record was the addition of a tropical storm in October 1966.
In that case, the system “was not in the database at all originally,” Landsea said. It was added based on three ship reports that recounted a storm with winds at or near 40 mph, as well as satellite imagery indicating a tropical cyclone of that magnitude.
“The satellites were a game-changer,” he said.
In the early 1960s, there were some satellite photos, but there was no consistency, Landsea said. About halfway through the decade, researchers could count on one picture a day and a composite view of the progress of a storm.
In making reassessments, the researchers not only use modern tools, but they comb through and correlate existing information such as Hurricane Center microfilm maps, historical weather maps, Navy reconnaissance records, hurricane hunters, published accounts, ships logs and reports, and the Mariners Weather Log.
The reassessment project is important not only to meteorologists. Accurate information is needed for formulating building codes, setting insurance rates, deciding where to build and where not to build, and predicting climate change outcomes.
The NOAA team is currently working on the review of storms in 1971-1975. Landsea said they already have drafted findings for 1971 and have almost completed 1972.
“I’m aiming for December 2023” to publish the report, he said.