Hypothetical Disasters Wiki
Hypothetical Disasters Wiki
2020 Alaska hurricane season
First storm formed April 17, 2020
Last storm dissipated November 8, 2020
Strongest storm Isabella – 140 mph (220 km/h), 951 mb (28.08 inHg)
Total depressions 14
Total storms 11
Hurricanes 7
Major hurricanes 4
Total damages $5.3 billion
Total fatalities 21

The 2020 Alaska hurricane season is an annual event in tropical cyclone formation in the Alaska Hurricane Center's (AHC) area of responsibility. The season began on May 1, 2020 and ended on November 30, 2020. However, the season's first tropical storm formed on April 17. This year, the AHC began using the Saffir-Simpson Hurricane Scale. It was an average season with 14 tropical depressions, 11 of them reached tropical storm strength.

Initial forecasts indicated an above average season, with the AHC forecasting 13-16 named storms, 4-7 hurricanes and 1-2 major hurricanes. The National Weather Service Forecast Office in Anchorage, however, was only forecasting 11 named storms.

The AHC's forecast area extends from 35°N to 80°N and 160°E to 120°W.


Hurricane Arianna

Category 1 hurricane
Counterclockwise vortex
Duration April 17 – April 22
Peak intensity 75 mph (120 km/h) (1-min)  987 mbar (hPa)

A stationary low pressure area persisted in the northern Pacific Ocean, about 1,300 miles north of Hawaii. This low gradually lost frontal characteristics and was given a 'high' chance of formation by the AHC early on April 17. It became Tropical Depression One-K later that day, and a special advisory was issued several hours later noting that the depression had strengthened. At that time, One-K was named 'Arianna'. The low strengthened further to 60 mph the following day. Arianna defied all forecasts and became the first hurricane of the season early on April 18. Later in the day, the hurricane weakened back to tropical storm status as cooler sea surface temperatures and dry air weakened the storm. While 300 miles south of the Aleutian Islands, the wind field of Arianna expanded, bringing strong winds to the islands. Late on April 21, Arianna weakened to a tropical depression due westerly 40-45 mph wind shear. The shear continued, and Arianna became a post-tropical remnant low on April 22. The remnant became a complex low with multiple fronts and brought up to 10 inches of rain to the Alaska Panhandle and the Cook Inlet area.

It was noted that Alaskan hurricanes typically move west to east south of the Aleutian Islands, not north towards them. The last hurricane to do this was Estelle last year.

Hurricane Brandon

Category 3 hurricane
Counterclockwise vortex
Duration May 29 – June 5
Peak intensity 120 mph (195 km/h) (1-min)  955 mbar (hPa)

On May 29, a tropical storm formed in the Gulf of Alaska without warning. Almost immediately, the storm was named Brandon and tropical storm warnings were issued from Kinak Bay to Controller Bay, Alaska. The storm rapidly intensified into a major hurricane within twelve hours. Brandon made landfall south of Anchorage with winds of 120 mph.

A state of emergency was declared for Alaska as the storm approached on June 3. Mandatory evacuations were ordered in Anchorage. Major flooding occurred, and preliminary damage totals were near $2 billion.

Tropical Storm Cadence

Tropical storm
Counterclockwise vortex
Duration June 13 – June 18
Peak intensity 50 mph (85 km/h) (1-min)  993 mbar (hPa)

A tropical depression developed on June 13, and was not expected to develop further. The system defied models and the AHC, and became Tropical Storm Cadence the next day.

Tropical Depression Four

Tropical depression
Counterclockwise vortex
Duration June 25 – June 28
Peak intensity 35 mph (55 km/h) (1-min)  1001 mbar (hPa)

The AHC began issuing advisories on Tropical Depression Four on June 25.

Tropical Storm David

Tropical storm
Counterclockwise vortex
Duration July 8 – July 16
Peak intensity 40 mph (65 km/h) (1-min)  997 mbar (hPa)

Hurricane Emma

Category 1 hurricane
Counterclockwise vortex
Duration July 30 – August 4
Peak intensity 80 mph (130 km/h) (1-min)  982 mbar (hPa)

Tropical Depression Seven

Tropical depression
Counterclockwise vortex
Duration August 3 – August 5
Peak intensity 35 mph (55 km/h) (1-min)  1005 mbar (hPa)

Hurricane Frank

Category 3 hurricane
Counterclockwise vortex
Duration August 12 – August 20
Peak intensity 120 mph (195 km/h) (1-min)  967 mbar (hPa)

Tropical Storm Grace

Tropical storm
Counterclockwise vortex
Duration August 24 – August 30
Peak intensity 65 mph (100 km/h) (1-min)  989 mbar (hPa)

Tropical Storm Hunter

Tropical storm
Counterclockwise vortex
Duration August 28 – September 1
Peak intensity 45 mph (75 km/h) (1-min)  1002 mbar (hPa)

Hurricane Isabella

Category 4 hurricane
Counterclockwise vortex
Duration September 6 – September 14
Peak intensity 140 mph (220 km/h) (1-min)  951 mbar (hPa)

Tropical Depression Twelve

Tropical depression
Counterclockwise vortex
Duration October 2 – October 6
Peak intensity 35 mph (55 km/h) (1-min)  1004 mbar (hPa)

On October 1, an area of strong thunderstorms developed 450 miles west of Seattle, Washington, and the AHC gave it a 30% chance of formation. Moving gradually west, it strengthened and advisories were initiated on Tropical Depression Twelve. Twelve continued westward and showed little sign of additional strengthening. Upper level wind shear ripped the system apart and dissipated on October 6 while 730 miles west of Juneau, Alaska.

Hurricane Jacob

Category 1 hurricane
Counterclockwise vortex
Duration October 28 – November 3
Peak intensity 75 mph (120 km/h) (1-min)  994 mbar (hPa)

Hurricane Kaitlyn

Category 4 hurricane
Counterclockwise vortex
Duration November 2 – November 8
Peak intensity 130 mph (215 km/h) (1-min)  955 mbar (hPa)


Saffir-Simpson Hurricane Scale

Storm names

Names were chosen by the AHC based on the top 100 Alaskan names. Names retired, if any, will be announced in August 2021.

  • Arianna
  • Brandon
  • Cadence
  • David
  • Emma
  • Frank
  • Grace
  • Hunter
  • Isabella
  • Jacob
  • Kaitlyn
  • Logan (unused)
  • Madison (unused)
  • Noah (unused)
  • Olivia (unused)
  • Preston (unused)
  • Rebecca (unused)
  • Seth (unused)
  • Trinity (unused)
  • Vance (unused)
  • Wanda (unused)