# Tropical cyclones in 2011

During 2011, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 131 tropical cyclones had formed this year to date. 71 tropical cyclones had been named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC). Thirty-nine of these named systems eventually intensified into hurricane-equivalent tropical cyclones. The most active basin in the year was the Western Pacific, which documented 21 named storms. North Atlantic basin documented 19 named storms, continuing the consecutive third-most active season trends from the previous year, due to the 2010–12 La Niña event. Conversely, the Eastern Pacific basin featured slightly more activity than the previous season, with 11 named storms. The least active basin in the year was the North Indian Ocean basin which documented only 2 named storms, the lowest since the 1993 season. Activity across the Southern Hemisphere were almost evenly spread, with the South-West Indian Ocean basin recording 10 tropical cyclones, the Australian region recording 17 tropical cyclones, and the South Pacific basin also recording 10 tropical cyclones, respectively. Twenty-one Category 3 tropical cyclones formed in the year, including three Category 5 tropical cyclones. The accumulated cyclone energy (ACE) index for the 2011 (seven basins combined), as calculated by Colorado State University was 573.8 units.
The strongest tropical cyclone of the year was Typhoon Songda, with a minimum central pressure of 920 hPa (mbar). The costliest tropical cyclone of the year was Hurricane Irene, which caused $14.2 billion worth of damage. The deadliest tropical cyclone of the year was Severe Tropical Storm Washi, which killed 2,546 people.

## Global atmospheric and hydrological conditions

The strong La Niña from the previous year continued into 2011, whereby it peaked in January. Afterwards, it began weakening considerably, to the point where in May it was determined that a transition to neutral conditions took place. By the end of Summer, this neutral state continued to persist, although there were still remnants of the La Niña evident. Due to continued cooling of the Pacific, it was determined that the La Niña redeveloped, albeit in a weak state, which would then continue into the next year.

## Systems
### January

During January 2011, a total of 12 tropical cyclones, all of them, formed within the southern hemisphere. No tropical cyclone was observed in the northern hemisphere. Of the systems, 7 further intensified to become named. Out of the systems, Wilma was the most intense tropical cyclone, with a minimum barometric pressure of 935 mbar/hPa.
Tropical cyclones formed in January 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| 03 | January 2–3 | 55 (35) | 996 | Madagascar | None | None |
| Vania | January 5–15 | 100 (65) | 973 | Vanuatu, Fiji, New Caledonia, New Zealand | unknown | unknown |
| 04F | January 5–7 | 185 (115) | 1002 | New Caledonia | $25 million | 3 direct, 1 indirect |
| Vince | January 10—15 | 75 (45) | 986 | None | None | None |
| Zelia | January 12—17 | 185 (115) | 943 | New Caledonia, Norfolk Island, New Zealand | None | None |
| Wilma | January 19–29 | 185 (115) | 935 | Samoan Islands, Tonga, New Zealand | $22 million | 3 |
| 07F | January 20–22 | 65 (40) | 996 | New Caledonia | None | None |
| Anthony | January 22–31 | 95 (60) | 989 | Queensland | Minor | None |
| Bianca | January 23–30 | 175 (110) | 949 | Northern Territory, Western Australia | Unknown | 2 |
| Yasi | January 26–February 3 | 205 (125) | 929 | Tuvalu, Fiji, Solomon Islands, Vanuatu, Papua New Guinea, Australia | $3.6 billion | 1 |
| 04 | January 30–31 | 45 (30) | 998 | Réunion | None | None |
| 13U | January 31 | Not Specified | Not Specified | None | None | None |

### February

10 systems formed and 5 named storms during February.
Tropical cyclones formed in February 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| BOB 01 | February 2–3 | 45 (30) | 1002 | Sri Lanka | 297 million | 18 |
| Zaka | February 5–7 | 95 (60) | 985 | None | None | None |
| 15U | February 8–13 | 55 (35) | 996 | None | None | None |
| Bingiza | February 9–17 | 155 (100) | 957 | Comoros, Madagascar | Unknown | 34 |
| Atu | February 13–24 | 165 (105) | 940 | Vanuatu | Unknown | None |
| Dianne | February 14–22 | 140 (85) | 960 | Western Australia | Minimal | None |
| Carlos | February 14–27 | 120 (75) | 969 | Northern Territory, Western Australia | $12.3 million | None |
| 06 | February 15–18 | 45 (30) | 1000 | None | None | None |
| 18U | February 23–28 | 55 (35) | 992 | None | None | None |
| 19U | February 26–March 1 | Not Specified | 1000 | Northern Territory | None | None |

### March

March was a relatively inactive month in which 11 systems formed, and only 3 received names.
Tropical cyclones formed in March 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| 20U | March 5 | Not Specified | Not Specified | None | None | None |
| 21U | March 7–8 | 45 (30) | 1004 | None | None | None |
| 12F | March 7–9 | 45 (30) | 1002 | Vanuatu | None | None |
| 22U | March 10–15 | Not Specified | Not Specified | None | None | None |
| Cherono | March 10–23 | 75 (45) | 993 | Rodrigues Island | None | None |
| Arani | March 14–16 | 85 (50) | 989 | Brazil | None | None |
| Bune | March 22 – 29 | 130 (80) | 967 | Fiji | None | None |
| 25U | March 26–April 6 | 55 (35) | 994 | None | None | None |
| 08 | March 29–31 | 45 (30) | 1004 | None | None | None |
| 26U | March 30–April 1 | Not Specified | 1006 | None | None | None |
| 27U | March 30–April 1 | Not Specified | 1006 | None | None | None |

### April

Tropical cyclones formed in April 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| 01W | April 1–4 | 55 (35) | 1004 | None | None | None |
| 02W (Amang) | April 3–6 | 55 (35) | 1000 | Mariana Islands | None | None |
| 14F | April 10–11 | Not Specified | 1005 | Vanuatu | None | None |
| 09 | April 11–16 | 95 (60) | 985 | None | None | None |
| 28U | April 14–15 | Not Specified | Not Specified | None | None | None |
| Errol | April 14–20 | 100 (65) | 986 | Indonesia, Western Australia, Northern Territory | None | None |
| 15F | April 15–17 | 55 (35) | 999 | None | None | None |
| 16F | April 28–30 | Not Specified | 1002 | None | None | None |

### May

May was a mostly inactive month in which only 4 tropical cyclones formed, in which 2 received names.
Tropical cyclones formed in May 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| Aere (Bebeng) | May 5–12 | 75 (45) | 992 | Philippines, Japan | $34.4 million | 48 |
| 17F | May 10–11 | 55 (35) | 1000 | None | None | None |
| Songda (Chedeng) | May 19–29 | 195 (120) | 920 | Micronesia, Philippines, Japan | $287 million | 17 |
| TD | May 31–June 1 | Not specified | 1004 | None | None | None |

### June

Tropical cyclones formed in June 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| Adrian | June 7–12 | 220 (140) | 944 | Southwestern Mexico | None | None |
| Sarika (Dodong) | June 8–11 | 75 (45) | 996 | Philippines, China | $248 million | 28 |
| ARB 01 | June 11–12 | 45 (30) | 996 | India | None | None |
| TD | June 14–15 | Not specified | 1004 | China | None | None |
| Haima (Egay) | June 16–25 | 75 (45) | 985 | Philippines, China, Vietnam, Laos, Thailand | $167 million | 18 |
| BOB 02 | June 16–23 | 65 (40) | 978 | India | None | 6 |
| Beatriz | June 19–22 | 150 (90) | 977 | Southwestern and Western Mexico | None | 4 |
| Meari (Falcon) | June 20–27 | 110 (70) | 970 | Philippines, China, Japan, Korea | $1.24 million | 11 |
| Arlene | June 28–July 1 | 100 (65) | 993 | Central America, Mexico, Texas, Florida | $223.4 million | 22 |

### July

Tropical cyclones formed in July 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| Calvin | July 7–10 | 130 (80) | 984 | None | None | None |
| Goring | July 8–10 | 45 (30) | 1000 | Taiwan, China | None | None |
| Ma-on (Ineng) | July 11–24 | 175 (110) | 935 | Northern Mariana Islands, Japan | $50 million | 5 |
| Tokage (Hanna) | July 13–15 | 65 (40) | 1000 | None | None | None |
| TD | July 16–17 | Not specified | 1000 | China | None | None |
| Bret | July 17–22 | 110 (70) | 995 | Bahamas, Bermuda, East Coast of the United States | None | None |
| Dora | July 18–24 | 250 (155) | 929 | Southwestern Mexico, Western Mexico, Baja California Peninsula, Southwestern United States | Minimal | None |
| Cindy | July 20–22 | 110 (70) | 994 | Bermuda | None | None |
| LAND 01 | July 22–23 | 35 (25) | 990 | India | None | None |
| Nock-ten (Juaning) | July 24–31 | 95 (60) | 985 | Philippines, China, Vietnam, Laos, Thailand | $126 million | 128 |
| Muifa (Kabayan) | July 25–August 9 | 175 (110) | 930 | Micronesia, Caroline Islands, Philippines, Japan, China, Korea, Russia | $480 million | 22 |
| Don | July 27–30 | 85 (50) | 997 | Cuba, Yucatán Peninsula, Northeastern Mexico, Texas | None | None |
| Lando | July 31–August 2 | Not specified | 1002 | Philippines | None | None |
| Eugene | July 31–August 6 | 220 (140) | 942 | None | None | None |

### August

August was the most active month of 2011, with 18 systems forming in the month.
Tropical cyclones formed in August 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| Emily | August 2–7 | 85 (50) | 1003 | Antilles, Florida, Bahamas | $5 million | 5 |
| Merbok | August 2–9 | 95 (60) | 980 | None | None | None |
| TD | August 2–4 | 55 (35) | 1008 | Japan | None | None |
| 13W | August 8–14 | 55 (35) | 1004 | None | None | None |
| TD | August 8–10 | 55 (35) | 1008 | None | None | None |
| Franklin | August 12–13 | 75 (45) | 1004 | Bermuda | None | None |
| Gert | August 13–16 | 100 (65) | 1000 | Bermuda | None | None |
| Fernanda | August 15–19 | 110 (70) | 992 | None | None | None |
| Greg | August 16–21 | 140 (85) | 979 | None | None | None |
| Harvey | August 19–22 | 100 (65) | 994 | Lesser Antilles, Hispaniola, Central America, Mexico | Minimal | 5 |
| TD | August 20–25 | 55 (35) | 1004 | None | None | None |
| Irene | August 21–28 | 195 (120) | 942 | Lesser Antilles, Greater Antilles, Turks and Caicos, Bahamas, East Coast of the United States, Vermont, Atlantic Canada | $14.2 billion | 58 |
| Nanmadol (Mina) | August 21–31 | 185 (115) | 925 | Philippines, Taiwan, China | $1.49 billion | 38 |
| Talas | August 23–September 5 | 95 (60) | 970 | Japan | $600 million | 82 |
| Ten | August 25–26 | 55 (35) | 1006 | None | None | None |
| Jose | August 26–29 | 75 (45) | 1006 | Bermuda | None | None |
| Katia | August 29–September 10 | 220 (140) | 942 | Lesser Antilles, East Coast of the United States, Canada, United Kingdom | $157 million | 4 |
| Eight-E | August 31–September 1 | 55 (35) | 1002 | Southwestern Mexico, Western Mexico | None | None |

### September

September was a below-average month, with only 16 tropical cyclones forming in that month.
Tropical cyclones formed in September 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| Unnamed | September 1–3 | 75 (45) | 1002 | None | None | None |
| Lee | September 2–5 | 95 (60) | 986 | Gulf Coast of the United States, Eastern United States | $2.8 billion | 18 |
| Noru | September 2–6 | 75 (45) | 990 | None | None | None |
| Kulap (Nonoy) | September 6–11 | 65 (40) | 1000 | Japan, Korea | None | None |
| Maria | September 6–16 | 130 (80) | 983 | Lesser Antilles, Bermuda, Newfoundland, Europe | $1.3 million | None |
| Nate | September 7–11 | 120 (75) | 994 | Mexico | Minimal | 5 |
| Roke (Onyok) | September 8–22 | 155 (100) | 940 | Japan, Russia, Alaska | $1.2 billion | 13 |
| TD | September 13–15 | Not specified | 1002 | Taiwan | None | None |
| Sonca | September 14–20 | 130 (80) | 970 | None | None | None |
| Ophelia | September 20–October 3 | 220 (140) | 940 | Leeward Islands, Bermuda, Newfoundland | Minimal | None |
| Hilary | September 21–30 | 230 (145) | 942 | Southwestern Mexico | Minimal | None |
| BOB 03 | September 22–23 | 45 (30) | 995 | India | Unknown | 42 |
| Nesat (Pedring) | September 23–30 | 150 (90) | 950 | Philippines, China, Vietnam | $2.12 billion | 98 |
| Haitang | September 24–27 | 65 (40) | 996 | China, Vietnam, Laos | $20 million | 25 |
| Philippe | September 24–October 8 | 150 (90) | 976 | Cape Verde | None | None |
| Nalgae (Quiel) | September 26–October 5 | 175 (110) | 935 | Philippines, China, Vietnam | $250 million | 18 |

### October

Tropical cyclones formed in October 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| Jova | October 6–13 | 205 (125) | 955 | Southwestern Mexico, Western Mexico | ≥$204 million | 9 |
| Irwin | October 6–16 | 155 (100) | 976 | Western Mexico | None | None |
| Banyan (Ramon) | October 9–14 | 65 (40) | 1002 | Palau, Philippines | $2.1 million | 10 |
| TD | October 10–13 | Not specified | 1006 | China, Vietnam | None | None |
| Twelve-E | October 12 | 35 (55) | 1004 | Southwestern Mexico, Central America | Unknown | 30 |
| BOB 04 | October 19–20 | 55 (35) | 1002 | Bangladesh, Myanmar | 1.64 million | 215 |
| Rina | October 23–28 | 185 (115) | 966 | Central America, Yucatán Peninsula, Cuba, Florida | $2.3 million | None |
| Keila | October 29–November 4 | 65 (40) | 996 | Oman, Yemen | $80 million | 14 |

### November

November was inactive with only 7 tropical cyclones forming, as well as Rolf, a system that formed in the Mediterranean sea.
Tropical cyclones formed in November 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| ARB 03 | November 6–10 | 55 (35) | 1000 | None | None | None |
| Rolf | November 6–9 | 85 (50) | 991 | Italy, France, Switzerland, Spain | >$1.25 billion | 12 |
| 24W | November 7–10 | 45 (30) | 1004 | Vietnam | None | None |
| Sean | November 8–11 | 100 (65) | 982 | Bermuda | Minimal | 1 |
| 01F | November 13–16 | Not Specified | 1004 | Fiji | None | None |
| Kenneth | November 19–25 | 230 (145) | 940 | None | None | None |
| ARB 04 | November 26–December 1 | 55 (35) | 998 | Lakshadweep, India, Sri Lanka, Maldives | Unknown | 19 |

### December

Tropical cyclones formed in December 2011 :
| Storm name | Dates active | Max wind km/h (mph) | Pressure (hPa) | Areas affected | Damage (USD) | Deaths |
| Alenga | December 3–11 | 140 (85) | 972 | None | None | None |
| 25W | December 4–5 | 45 (30) | 1006 | Brunei, Malaysia | None | None |
| 02 | December 6–9 | 55 (35) | 998 | Mauritius | None | None |
| 26W | December 10–14 | 55 (35) | 1004 | Philippines | None | 4 |
| Washi (Sendong) | December 13–19 | 95 (60) | 992 | Philippines, Micronesia, Palau | $97.8 million | 2,546 |
| Fina | December 18–23 | 65 (40) | 994 | Papua New Guinea, New Caledonia | None | None |
| 03 | December 19–23 | 55 (35) | 1000 | Madagascar | None | None |
| Benilde | December 21–January 4 | 150 (90) | 968 | None | None | None |
| Grant | December 21–January 2 | 100 (65) | 978 | Northern Territory | Minor | None |
| TD | December 24 | Not specified | 1002 | None | None | None |
| Thane | December 25–December 31 | 140 (85) | 969 | India, Sri Lanka | $235 million | 46 |
| 05U | December 26–28 | Not Specified | Not Specified | None | None | None |
| 02F | December 28–January 1 | Not Specified | 1002 | Niue, Cook Islands | None | None |
| TD | December 31–January 1 | Not specified | 1008 | Malaysia | None | None |

## Global effects

| Season name | Areas affected | Systems formed | Named storms | Damage (USD) | Deaths |
| 2011 Atlantic hurricane season $^1$ | Central America, Mexico, Texas, Florida, Bahamas, Bermuda, East Coast of the United States, Cuba, Yucatán Peninsula, Northeastern Mexico, Antilles, Lesser Antilles, Hispaniola, US Virgin Islands, Puerto Rico, Lucayan Archipelago, Eastern United States, North Carolina, New Jersey, Canada, Gulf Coast of the United States, Newfoundland, Europe, Leeward Islands, Quintana Roo, | 20 | 18 | $17.39 billion | 118 |
| 2011 Pacific hurricane season $^1$ | Southwestern Mexico, Western Mexico, Baja California Peninsula, Southwestern United States, Central America | 13 | 11 | $203.67 million | 43 |
| 2011 Pacific typhoon season $^2$ $^3$ | Mariana Islands, Philippines, Japan, Micronesia, China, Vietnam, Laos, Thailand, Korea, Taiwan, Caroline Islands, Palau, Malaysia | 39 | 21 | $7.68 billion | 3,111 |
| 2011 North Indian Ocean cyclone season | Sri Lanka, India, Bangladesh, Myanmar, Oman, Yemen, Lakshadweep, | 10 | 2 | $603.64 million | 367 |
| 2010–11 South-West Indian Ocean cyclone season $^2$ | Comoros, Madagascar, Réunion | 7 | 2 | None | 34 |
| 2011–12 South-West Indian Ocean cyclone season $^3$ | Madagascar | 3 | 2 | None | None |
| 2010–11 Australian region cyclone season $^2$ | Northern Territory, Western Australia, Solomon Islands, Indonesia | 19 | 7 | $2.7 billion | 3 |
| 2011–12 Australian region cyclone season | Papua New Guinea, Northern Territory | 4 | 2 | None | None |
| 2010–11 South Pacific cyclone season $^2$ | Fiji, Vanuatu, New Caledonia, New Zealand, Norfolk Island, Samoan Islands, Tonga | 15 | 7 | >$33 million | 14 |
| 2011–12 South Pacific cyclone season $^3$ | Fiji, Niue, Cook Islands | 2 | 0 | None | None |
| South Atlantic tropical cyclone | Brazil | 1 | 1 | None | None |
| Mediterranean tropical-like cyclone | Italy, France, Switzerland, Spain | 1 | 1 | > $1.25 billion | 12 |
| Worldwide | (See above) | 134 | 74 | $29.86 billion | 3,702 |
* ↑ The sum of the number of systems and fatalities in each basin will not equal the number shown as the total. This is because when systems move between basins, it creates a discrepancy in the actual number of systems and fatalities.