*A year-end wrap-up…US wildfires down…US tornadoes most since 2019…an active tropical season, but most activity stayed over the Atlantic...other important tropical metrics nearly normal*
Paul Dorian
The vast majority of the named storms in 2023 stayed out over the open waters of the Atlantic Ocean.
Overview
The end of the year is closing in rapidly and this blog provides a wrap up of the 2023 US wildfire and tornado seasons and also the 2023 tropical season in the Atlantic Basin.
2023 US Wildfire Season
The news has been quite good this year with respect to the total number of acres burned on US soil due to wildfire activity. In fact, the total acreage burned this year is under 3 million (through 12/18) which is far below the 10-year average of nearly 7 million from 2013-2022 and the lowest since 1998.
Data source: https://www.nifc.gov/fire-information/nfn
One of the main contributing factors to the down year in overall US wildfire activity is the fact that it has been a mild year in California with the number of burned acres under 390,000 (as of 12/18). This value is down about 75% from the 5-year average of about 1.6 million acres burned in the Golden State (data source). The relatively mild year of 2023 follows another relatively mild year in 2022; however, the two years before that (2020, 2021) were some of the worst on record.
The path of Tropical Storm Hilary which brought rainfall to southern California during the middle of August. Credit: Wikipedia
The weather during 2023 played an important role in keeping wildfire activity on the mild side across California. To begin, the winter of 2022-2023 brought very high precipitation amounts to the Golden State with record-breaking snow amounts at the higher elevations (e.g., Sierra Nevada). The melting of the snow this past summer season indeed lasted as late as ever in some spots helping to keep plenty of soil on the wet side across portions of California. Also, the wildfire season of summer and fall featured overall cooler than normal conditions helping to inhibit wildfire formation and expansion. Finally, Tropical Storm Hilary made a visit to the southern part of the state during the middle of August and the precipitation from this storm played a beneficial role in inhibiting wildfires during the all-important late summer and early fall time period.
2023 US Tornado Season
While the number of tornadoes reported this year across the US was the highest since 2019, they were below-normal as far as “inflation-adjusted” percentile rankings are concerned where preliminary reports are multiplied by 0.85 to remove overcount. As of December 25th, the “inflation-adjusted” number of tornadoes was 1210 which is closer to the 25th percentile of 1189 than it is to the 50th percentile of 1292 (which represents “normal”) according to NOAA’s Storm Prediction Center.
Data source: https://www.spc.noaa.gov/wcm/adj.html
The actual number of preliminary tornadoes reported of 1423 (through 12/25), was higher than last year’s 1331 and the most since 2019 when 1677 were observed and it falls above the mean of 1380 from 2005 to 2022.
Data source: https://www.spc.noaa.gov/climo/summary/
The year started off quite active with respect to tornadoes with January featuring the third highest number of tornadoes of any January on record. In fact, the first two months of the year combined saw the fourth-highest number of confirmed tornadoes of any on record. The most recent outbreak of tornadoes took place in Tennessee on December 9th when a strong storm system pushed up through the eastern states from the south-central US. There were six fatalities in Tennessee on that day and tragically, this year has been deadlier than average with multiple fatal tornadoes.
2023 Tropical Season in the Atlantic Basin
While the 2023 hurricane season in the Atlantic Basin was well above-normal in terms of the number of named storms, the news was not all bad with respect to the overall tropical season. Other important metrics were actually quite close to climatological averages, and the best news of all was that the vast majority of the named storms spent most, if not all, of their time harmlessly out over the open waters of the Atlantic Ocean. In fact, despite the active season in 2023, the only US landfalling hurricane was Hurricane Idalia which made landfall as a category-3 hurricane on August 30th near Keaton Beach, Florida. In addition, Tropical Storm Ophelia made landfall as a strong tropical storm with 70 mph winds on Emerald Isle, North Carolina on September 23rd. Hurricane Lee made landfall as a post-tropical cyclone in Nova Scotia, Canada, on September 16th and swells generated by Lee caused dangerous surf and rip currents along the entire U.S. Atlantic coast.
The figure above shows tropical cyclones of hurricane strength (i.e., Category 1+) that made landfall along the continental United States (CONUS) from 1900 to 2023. There was one landfall in 2023, Hurricane Idalia in Florida. Data courtesy Roger Pielke, Jr., Philip Klotzbach (link)
In terms of specifics, there were 20 named storms in 2023 having reached at least “tropical storm” status according to NOAA’s National Hurricane Center. This year’s total is well above the normal of 14.3 when using the base period of 1991-2020 for comparison. In fact, the total of 20 named storms in 2023 ranks fourth for the most-named storms since 1950. However, despite the higher-than-normal number of named storms, the number that reached hurricane status (7) and the number of major hurricanes (3) fell very close to the long-term climatological averages of 7.2 and 3.2 respectively. Aided by the high number of named storms, the metric known as the accumulated cyclone energy or ACE was measured at 145.6 versus the climatological average of 122.5.
The figure above shows tropical cyclones of major hurricane strength (i.e., Category 3+) that made landfall along the continental United States, with Hurricane Idalia in 2023 making landfall as a Category 3 storm. There are no trends in either landfalling CONUS hurricanes or major hurricanes from 1900 to 2023. Data courtesy Roger Pielke, Jr., Philip Klotzbach (link)
The active tropical season in the Atlantic Basin in 2023 took place despite an El Nino that developed in the tropical Pacific Ocean earlier in the year. El Nino is characterized by warmer-than-normal sea surface temperatures in the equatorial part of the Pacific Ocean. This usually results in a less active tropical season in the Atlantic Basin as El Nino often produces higher wind shear in the important breeding grounds of the tropical Atlantic. A counterbalance this year to the normally unfavorable impacts associated with El Nino was the abnormally warm ocean waters in the Atlantic Ocean which is favorable for tropical storm formation and intensification.
Signs point to a quick demise of El Nino in the tropical Pacific by late this winter or next spring with a flip back to La Nina. This plot shows numerous computer forecast models predicting a significant drop in sea surface temperatures across the central tropical Pacific Ocean by the time we get into the heart of the 2024 tropical season. This change back to colder-than-normal water (i.e., La Nina) in the equatorial Pacific could very well lead to a very active tropical season in 2024 across the Atlantic Basin.
Looking ahead, El Nino is quite likely to weaken later this winter season and could actually flip back to La Nina conditions (colder-than-normal water) in the equatorial Pacific in time for the 2024 Atlantic Basin tropical season. This could very well result in a very active tropical season in 2024 as traditionally, La Nina is quite favorable for tropical storm formation and intensification in the Atlantic Basin.
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com