Batten down for a rough hurricane season
By Josh Rhoten
Colorado State University hurricane researchers are predicting an extremely active Atlantic hurricane season in their initial 2024 forecast.
The team cites record warm tropical and eastern
subtropical Atlantic sea surface temperatures as a primary factor for their
prediction of 11 hurricanes this year.
When waters in the eastern and central tropical and subtropical Atlantic are much warmer than normal in the spring, it tends to force a weaker subtropical high and associated weaker winds blowing across the tropical Atlantic.
While the tropical Pacific is currently characterized by El Niño conditions, these are likely to transition to La Niña conditions by the peak of the Atlantic hurricane season from August to October.
La Niña tends to decrease upper-level westerly winds across the
Caribbean into the tropical Atlantic. These decreased upper-level winds result
in reduced vertical wind shear, favoring Atlantic hurricane formation and
intensification.
Given the combined hurricane-favorable signals of an extremely warm Atlantic and a likely developing La Niña, the forecast team has higher-than-normal confidence for an April outlook that the 2024 Atlantic hurricane season will be very active.
This is the highest prediction for hurricanes that CSU has ever issued with their April outlook. The prior highest April forecast was for nine hurricanes, which has been called for several times since the university began issuing April forecasts in 1995.
However, the team stresses that the April outlook
historically has the lowest level of skill of CSU’s operational seasonal
hurricane forecasts, given the considerable changes that can occur in the
atmosphere-ocean between April and the peak of the Atlantic hurricane season
from August–October.
Tropical Weather and Climate Research Team predicts 23
named storms in 2024
The CSU
Tropical Weather and Climate Research Team is predicting 23
named storms during the Atlantic hurricane season, which runs from June 1 to
Nov. 30. Of those, researchers forecast eleven to become hurricanes and five to
reach major hurricane strength (Saffir/Simpson Category 3-4-5) with sustained
winds of 111 miles per hour or greater.
The team bases its forecasts on a statistical model, as well as four models that use a combination of statistical information and model predictions of large-scale conditions from the European Centre for Medium-Range Weather Forecasts, the UK Met Office, the Japan Meteorological Agency, and the Centro Euro-Mediterraneo sui Cambiamenti Climatici.
These models use 25-40 years of historical hurricane seasons and
evaluate conditions including: Atlantic sea surface temperatures, sea level
pressures, vertical wind shear levels (the change in wind direction and speed
with height in the atmosphere), El Niño (warming of waters in the central and
eastern tropical Pacific), and other factors.
So far, the 2024 hurricane season is
exhibiting characteristics similar to 1878, 1926, 1998, 2010 and 2020.
“Our analog seasons were all very
active Atlantic hurricane seasons,” said Phil Klotzbach, senior research
scientist in the Department of Atmospheric Science at CSU and
lead author of the report. “This highlights the somewhat lower levels of
uncertainty that exist with this outlook relative to our typical early April
outlook.”
The team predicts that 2024 hurricane activity will be about 170% of the average season from 1991–2020. By comparison, 2023’s hurricane activity was about 120% of the average season.
The
most significant hurricane of the 2023 Atlantic hurricane season was Hurricane
Idalia. Idalia made landfall at Category 3 intensity in the Big Bend region of
Florida, causing $3.6 billion dollars in damage and resulting in eight direct
fatalities.
In addition to the various hurricane metrics that CSU has used for many years, the forecast team introduced a new metric last year. Accumulated Cyclone Energy (ACE) occurring west of 60 degrees west longitude is an integrated metric accounting for storm frequency, intensity and duration in the western half of the Atlantic basin.
ACE generated
west of 60 degrees west correlates better with landfalling storms in the
Atlantic basin than basinwide ACE, since virtually all hurricane-prone
landmasses in the Atlantic Ocean are located west of 60 degrees west.
Generally, a slightly lower
percentage of basinwide ACE occurs west of 60 degrees west in El Niño years
relative to La Niña years. Since the team anticipates La Niña as the most
likely outcome in 2024, the percentage of basinwide ACE occurring west of 60
degrees west is predicted to be higher than last year.
The CSU team will issue forecast
updates on June 11, July 9 and Aug. 6.
The CSU forecast is intended to provide a best estimate of activity in the Atlantic during the upcoming season – not an exact measure.
As always, the researchers caution
coastal residents to take proper precautions.
“It takes only one storm near you to
make this an active season for you,” Bell said.
Atlantic hurricane landfalling probability included in
2024 report
The report also includes the
probability of major hurricanes making landfall:
- ·
62% for the entire U.S. coastline
(average from 1880–2020 is 43%).
- ·
34% for the U.S. East Coast,
including the Florida peninsula (average from 1880–2020 is 21%).
- ·
42% for the Gulf Coast from the
Florida panhandle westward to Brownsville (average from 1880–2020 is 27%).
- ·
66% for the Caribbean (average from
1880–2020 is 47%).
The forecast team also provides
probabilities of named storms, hurricanes and major hurricanes tracking within
50 miles of each county or parish along the Gulf and U.S. East Coast, as well
as hurricane-prone coastal states, Mexican states, Canadian provinces and
countries in Central America and the Caribbean. These probabilities for regions
and countries are adjusted based on the current seasonal forecast.
This is the 41st year that CSU has issued an Atlantic basin seasonal hurricane forecast. Professor Emeritus Bill Gray originated the seasonal forecasts at CSU and launched the report in 1984. He continued to author them until his death in 2016. The authors of this year’s forecast are Phil Klotzbach, Professor Michael Bell, Ph.D. candidate Alex DesRosiers, and Research Scientist Levi Silvers. The CSU Tropical Weather and Climate Team is part of the Department of Atmospheric Science in the Walter Scott, Jr. College of Engineering at CSU and is one of the top ranked Atmospheric Science programs in the world.
Funding for this year’s report has
been provided by Ironshore Insurance, the Insurance Information Institute,
Weatherboy, Insurance Auto Auctions and a grant from the G. Unger Vetlesen
Foundation.
