Categories
Environment

2021 Atlantic Hurricane Season Forecast

2021 is likely to be “near normal” in terms of tropical activity, though there is more risk of an active season. Impacts from landfalling hurricanes could shift eastward this season toward the U.S. East Coast and the Leeward Islands. 

The forecast for the 2021 Atlantic Hurricane Season from June-November shows the likelihood for a near normal season, with 

  • tropical cyclone activity at ~107% of normal anticipated 
  • range of activity from 97-119% of normal 
  • 17 named storms (average 14)
  • 8 hurricanes  (average 7)
  • 3 major hurricanes (average 3)

Unlike last season, the 2021 outlook does not include a hyperactive season within the expected range of outcomes, though there is very little chance for below normal activity this season. It should be noted that a “normal hurricane season” now represents higher levels of tropical activity in all aspects because of the climatology update uses 1991-2020 as the baseline instead of 1981-2010 period used previously. If 2021 outlook was issued based on the previous climatology, the forecast would call for an active season instead of a near normal one. 

2021 Storm Forecast (red) compared to normal (blue)
2021 Storm Forecast (red) compared to normal (blue)

The Greek alphabet will no longer be used to extend the named storms’ list. If all names in the first list have been used, a supplemental list will begin.

Background:
The major ocean basins’ data support a near to above normal season of tropical activity once again. Beginning with ENSO (El Niño Southern Oscillation), there is an 80% chance of neutral or La Niña conditions being in place by the August-October peak of hurricane season, with only a 20% chance of El Niño. 

La Niña is the most favorable state for active Atlantic seasons as it supports low vertical wind shear needed for tropical cyclone formation and intensification, so the strong likelihood of neutral or La Niña conditions in 2021 suggests an active year while the slight El Niño chance reduces that potential. 

The Atlantic Multi-decadal Oscillation (AMO) shows an 80% chance to be in its favorable warm Sea Surface Temperature (SST) phase for Atlantic tropical activity. 

The largest question is the Indian Ocean Dipole (IOD), which has a connection to Atlantic occurrence of dry air that suppresses tropical cyclone formation. In 2021, there are questions about the state of the IOD by August-October, which supports a nearer to normal hurricane season. 

The most reliable forecast variable is Accumulated Cyclone Energy (ACE), which is widely viewed as the best measure of cyclone activity instead of the total named storm number and hurricane number. Since tropical cyclones vary wildly in duration from 1-10+ days, similar numbers of storms in different years can still represent very different levels of activity. 

The spread among the storms is relatively narrow, with 20% of the years showing below normal activity while the other 80% showed above normal activity. Due to the narrow range among prior years relative to the new normal level of activity, 100% of the prior years used in the forecast are in the “near normal” range. This results in a high confidence outlook for near to above normal activity in 2021, with the direction of ENSO and the IOD being the key issues to monitor.  

The data used in the forecast and current SST anomalies both indicate the U.S. East Coast being at the greater risk for higher impacts than usual, based on warm ocean waters off the coastline. If the model holds, any developing tropical cyclone that moves across the Western Atlantic approaching the U.S. will have ample energy to become a high-impact hurricane if other environmental conditions allow. There is also a consensus for slightly warmer than normal SST around the Leeward Islands of the Caribbean Sea, making that another area to watch for high-end impacts this season. Gulf of Mexico SST is not low but  not near the record warmth of last year. 

Annual Atlantic seasonal  tropical cyclone activity from 1982-2021, with 2000, 2008, 2011, 2012, and 2018 highlighted in red for active, green for inactive seasons (June-November), and the 2021 forecast highlighted in purple.
Annual Atlantic seasonal  tropical cyclone activity from 1982-2021, with 2000, 2008, 2011, 2012, and 2018 highlighted in red for active, green for inactive seasons (June-November), and the 2021 forecast highlighted in purple.
Categories
Environment

2017 Atlantic Hurricane Season Forecast

The season’s first updated June forecast for Atlantic hurricanes in 2017 has been released by the Colorado State University Tropical Meteorology Project.

(April 6 ) This year, 2017, the expectation is for a “below average” year, based on 29 years of observations from 1981 to 2010. There is the potential for shear-enhancing El Niño conditions to develop over the next several months. The tropical Atlantic has cooled over the past month, and the far North Atlantic is currently colder than normal. These cold anomalies tend to force atmospheric conditions that are less conducive for Atlantic hurricane formation and intensification.

(June 1) We have increased our forecast and now believe that 2017 will have approximately average activity. The odds of a significant El Niño in 2017 have diminished somewhat, and portions of the tropical Atlantic have anomalously warmed over the past two months. While the tropical Atlantic is warmer than normal, the far North Atlantic remains colder than normal, potentially indicative of a negative phase of the Atlantic Multi-Decadal Oscillation. We anticipate a near-average probability for major hurricanes making landfall along the United States coastline and in the Caribbean.

August 2004, Hurricane Charley washed out part of Captiva Island.
August 2004, Hurricane Charley washed out part of Captiva Island.

From http://tropical.colostate.edu :-

We anticipate that the 2017 Atlantic basin hurricane season will have slightly below- average activity. The current neutral ENSO is likely to transition to either weak or moderate El Niño conditions by the peak of the Atlantic hurricane season. The tropical Atlantic has anomalously cooled over the past month and the far North Atlantic is relatively cold, potentially indicative of a negative phase of the Atlantic Multi-Decadal Oscillation. We anticipate a below-average probability for major hurricanes making landfall along the United States coastline and in the Caribbean. As is the case with all hurricane seasons, coastal residents are reminded that it only takes one hurricane making landfall to make it an active season for them. They should prepare the same for every season, regardless of how much activity is predicted.
by Philip J. Klotzbach and Michael M. Bell (as of 6 April 2017)

An analysis of a variety of different atmosphere and ocean measurements (through March) which are known to have long-period statistical relationships with the upcoming season’s Atlantic tropical cyclone activity indicate that 2017 should have slightly below-average activity. The big question marks with this season’s predictions are whether an El Niño develops, as well as what the configuration of Sea Surface Temperatures will look like in the tropical and far North Atlantic Ocean during the peak of the Atlantic hurricane season.

June 1 – Our confidence that a weak to moderate El Niño will develop has diminished since early April. While upper ocean content heat anomalies have slowly increased over the past several months, the transition towards warm ENSO conditions appears to have been delayed compared with earlier expectations. At this point, we believe that the most realistic scenario for the 2017 Atlantic hurricane season is borderline warm neutral ENSO to weak El Niño conditions. There remains a need to closely monitor ENSO conditions over the next few months. Additional discussion of ENSO will be included with the July 1 and August 4 updates.

2017 Forecast numbers:

Atlantic Hurricane SeasonApril    June 2017 forecast29-year Median
Named storms (>35mph winds) 11         13
12
Hurricanes (>72mph winds) 4             6
6.5
Major hurricanes (>111mph winds) 2             22
US landfall likelihood42%        55%52%
Gulf Coast landfall probability24%        32%30%
Major Hurricane in Caribbean
probability
34%        44%42%
Manatee County hurricane landfall
probability
0.6%        0.7%0.7%
Manatee County tropical storm
probability
14.7%      18.3%17.1%
Manatee County >75mph wind gusts
probability
4.2%        5.4%5.0%
Tracks of major hurricanes making Florida peninsula and East Coast landfall during 1916-1965 and 1966-2015.
Tracks of major hurricanes making Florida peninsula and East Coast landfall during 1916-1965 and
1966-2015.
Categories
Environment

2016 Atlantic Hurricane Season Review

2016-hurricane-tracks
2016 Atlantic storm tracks

Summary:

  • Slightly above average storm activity
  • Flooding impacts on Anna Maria Island (Colin and Hermine)
  • 2 landfalls on Florida Gulf Coast (Colin and Hermine)
  • 11-year record lull of no major hurricane landfalls on Florida
  • 1 major hurricane came within 50 miles of Florida East Coast (Cat 5 Mathew)
Atlantic Hurricane Season April 2016 forecast 2016 Actual
Named storms (>35mph) 12 15
Hurricanes (>72mph) 5 7
Major hurricanes (>111mph) 1 3
US landfall likelihood 50% 33%
Gulf Coast landfall 30% 13%

The Named Storms:

Alex – Hurricane Cat 1 Jan 13-15 pre-season in Eastern Atlantic

Bonnie – Tropical Storm May 27 – Jun 4 weak South Carolina landfall

Colin – Tropical Storm Jun 5 – 7 High tide flooding on Anna Maria Island

Danielle – Tropical Storm Jun 19 – 21 affecting Yucatan Peninsula and eastern Mexico

Earl – Hurricane Cat 1 Aug 2 – 6 affecting Antilles, Dominican Republic, Belize and Mexico

Fiona – Tropical Storm Aug 17 – 23 no effects on land

Gaston – Hurricane Cat 3 Aug 22 – Sep 3 no effects on land

Hermine – Hurricane Cat 1 Aug 28 – Sep 3 Rain and high tide flooding on Anna Maria Island landfall in Big Bend of Florida

Ian – Tropical Storm Sep 12 – 16 no effects on land

Julia – Tropical Storm Sep 14 – 18 Formed over Florida but main impact was on North Carolina and Virginia

Karl – Tropical Storm Sep 14 – 25 affecting Bermuda

Lisa – Tropical Storm Sep 19 – 24 no effects on land

Mathew – Hurricane Cat 5 Sep 28 – Oct 9 Landfall in Haiti, Cuba, Bahamas. Close to but not making landfall on Florida East Coast

Nicole – Hurricane Cat 4 Oct 4 – 18 Affecting Bermuda, US East Coast and Canada

Otto – Hurricane Cat 2 Nov 21 – 25 late season landfall in Nicaragua re-emerging in Eastern Pacific

Categories
Environment

2016 Atlantic Hurricane Season Forecast

The season’s first forecast for Atlantic hurricanes in 2016 has been released by the Colorado State University Tropical Meteorology Project. After 10 years of below average activity, this year the expectation is for an “average” year. That is, a return to mean as recorded over the past 29 years of their data.

The strong El Nino effect in the Pacific during the past year has deflected storms and reduced winds aloft over the US mainland but is expected to weaken during this coming summer due to colder temperatures in the North Atlantic. By September the El Nino influence is expected to be gone, just in time for the peak of the Atlantic hurricane season, however, subsequently moderate La Nina conditions in late summer and fall could bring significant cooling.

We anticipate that the 2016 Atlantic basin hurricane season will have approximately average activity. The current weakening El Niño is likely to transition to either neutral or La Niña conditions by the peak of the Atlantic hurricane season. While the tropical Atlantic is relatively warm, the far North Atlantic is quite cold, potentially indicative of a negative phase of the Atlantic Multi-Decadal Oscillation. We anticipate a near-average probability for major hurricanes making landfall along the United States coastline and in the Caribbean. As is the case with all hurricane seasons, coastal residents are reminded that it only takes one hurricane making landfall to make it an active season for them. They should prepare the same for every season, regardless of how much activity is predicted.

–  Dr. Philip J. Klotzbach, Colorado State University 14 April, 2016

 

Atlantic Hurricane Season April 2016 forecastAverage
Named storms (>35mph winds)  12
 12
Hurricanes (>72mph winds)  5  6.5
Major hurricanes (>111mph winds)  1  2
US landfall likelihood 50% 52%
Gulf Coast landfall probability 30% 30%
Major Hurricane in Caribbean probability 29% 42%
Manatee County hurricane landfall probability* 0.6% 0.7%
Manatee County tropical storm probability* 16.3% 17.1%
Manatee County >75mph wind gusts probability* 4.7% 5.0%

Tracks of major hurricanes making Florida peninsula and East Coast landfall during 1916-1965 and 1966-2015.
Tracks of major hurricanes making Florida peninsula and East Coast landfall during 1916-1965 and 1966-2015.

The last hurricane effect in the Tampa Bay area was the Tarpon Springs hurricane of October, 1921. Anna Maria Island’s first bridge from Cortez, being constructed at the time, was damaged in the storm.

Anna Maria Island's last close-by hurricane made landfall at Tarpon Springs.
Anna Maria Island’s last close-by hurricane made landfall at Tarpon Springs.
Categories
Environment

2015 Atlantic Hurricane Season Review

2015 Atlantic Storm tracks
2015 Atlantic Storm tracks

Summary:

  • Below average storm activity with fewest named storms since 1993
  • No impacts on Anna Maria Island
  • No landfalls on Florida
  • A record 65-straight hurricanes in the Atlantic have missed Florida
  • Last storm (Wilma) to hit Florida was 10 year ago, an all time record lull.
  • 1 Gulf of Mexico storm (TS Bill)
  • 1 US mainland landfall (TS Ana, pre hurricane season)
  • 2 major hurricanes (Cat 3 Danny and Cat 4 Joaquin)
Atlantic Hurricane Season April 2015 forecast 2015 Actual
Named storms (>35mph) 7 11
Hurricanes (>72mph) 3 4
Major hurricanes (>111mph) 1 2
US landfall likelihood 28% 9%
Gulf Coast landfall 15% 9%

The Named Storms:

Ana – Tropical Storm, May 8-11. Earliest on record. Landfall North Myrtle Beach, South Carolina.

Bill – Tropical Storm, June 16-18. Landfall Matagorda Island, Texas.

Claudette – Tropical Storm, July 13-14

Danny – Hurricane Cat 3, August 18-24

Erika – Tropical Storm, August 25-29, impacting Dominica, Guadalupe, Puerto Rico, and Haiti.

Fred – Hurricane Cat 1, August 30 to September 6, first ever impact on Cape Verde Islands.

Grace – Tropical Storm, September 5-9

Henri – Tropical Storm, September 8-11

Ida – Tropical Storm, September 18-27

Joaquin – Hurricane Cat 4, September 28 to October 8, impacting Bahamas, and sinking cargo ship El Faro.

Kate – Tropical Storm, November 9-12