Arizona has been affected by hurricanes on numerous occasions. Usually, these storms originate in the eastern Pacific Ocean, make landfall in the Mexican states of Baja California or Sonora, and dissipate before crossing into the United States. Thus, in most cases, it is only the tropical cyclones' remnant moisture that produces heavy rainfall—and in some occasions, flooding—in portions of Arizona. However, approximately every five years, a tropical cyclone retains sufficient strength to enter the state as a tropical storm or a tropical depression. Arizonans can expect indirect flash floods caused by the remnants of tropical cyclones to occur about every two years. [1]
Tropical cyclones in Arizona are not common, since the predominant wind pattern steers most storms that form in the Eastern Pacific either parallel or away from the Pacific coast of northwestern Mexico. As a result, most storms that could affect Arizona are carried away from the United States, with only 6% of all Pacific hurricanes entering US territory. [2] Not all Arizona hurricanes originate from the Pacific Ocean, however; in July 2008, an Atlantic hurricane named Hurricane Dolly produced rainfall in the eastern portion of the state, and another Atlantic storm reached Arizona as a tropical depression. Many, but not all, of these systems also impacted California.
Despite their rarity, tropical cyclones are among Arizona's most significant weather makers. In years when Arizona is affected by a tropical cyclone, these can be responsible for up to 25% of the rainfall in areas along the Colorado River. Arizona hurricanes are also responsible for torrential rains in localized areas, with the state's 24-hour rainfall record—11.97 inches (304 mm) of precipitation [3] —occurring during Hurricane Nora's landfall in 1997. The heavy rainfall can trigger extensive flash floods, such as the ones produced by the remnants of Tropical Storm Octave in 1983, or the lingering moisture from Tropical Storm Emilia in 2006.
Precipitation | Storm | Location | Ref. | ||
---|---|---|---|---|---|
Rank | mm | in | |||
1 | 344.4 | 13.56 | Unnamed 1951 | Crown King | [4] |
1 | 305.1 | 12.01 | Nora 1997 | Harquahala Mountains | [5] |
2 | 304.8 | 12.00 | Octave 1983 | Mount Graham | [5] |
3 | 289.6 | 11.40 | Norma 1970 | Workman Creek | [4] |
4 | 210.8 | 8.30 | Heather 1977 | Nogales | [5] |
5 | 209.8 | 8.26 | Unnamed 1926 | Hereford | [4] |
6 | 178.6 | 7.03 | Unnamed 1939 | Wikieup | [4] |
7 | 178.1 | 7.01 | Doreen 1977 | Yuma Valley | [5] |
8 | 177.8 | 7.00 | Javier 2004 | Walnut Creek | [5] |
9 | 166.9 | 6.57 | Newton 2016 | Rincon Mountains | [6] |
10 | 158.8 | 6.25 | Norbert 2014 | Tempe 3.1 WSW | [4] |
Tropical cyclones are not common over Arizona, but on average, a tropical storm or a tropical depression affects the state approximately every five years. However, indirect flash floods caused by the remnants of tropical cyclones are more common, as they tend to occur about every two years. [1]
Storms that approach the southwestern United States, specifically Arizona, generally track closer to the Mexican coast than average, making them more likely to recurve northwards under the influence of an approaching trough. These troughs tend to extend farther to the south during the latter part of the Pacific hurricane season, in the period between late August and early October. These pronounced troughs thus produce a synoptic-scale flow that is conducive to steering hurricanes towards the southwestern United States. [7] All of the systems that have impacted Arizona have formed in the Pacific hurricane season, and only storm remnants have affected the state before August. [2]
The infusions of tropical moisture from tropical cyclones can be a significant portion of the annual rainfall in the region. In years when storms approach Arizona, eastern and northern portions of the state receive on average 6–8% of the monsoon-season precipitation from tropical systems and their remnants. This percentage rises towards the southwestern corner of the state, which can receive up to a quarter of its monsoon-season rainfall from tropical cyclones. [7] [8]
Month | Number of storms |
---|---|
June | |
July | |
August | |
September | |
October |
Storm | Peak intensity | Season | Intensity | Date [9] |
---|---|---|---|---|
Unnamed [10] | Unknown | 1921 | Remnant low | August 20, 1921 |
Unnamed [11] | Unknown | 1921 | Tropical depression | September 30, 1921 |
Unnamed [9] | Unknown | 1926 | Remnant low | September 20, 1926 |
Unnamed [9] | Unknown | 1927 | Remnant low | September 7, 1927 |
One [12] | Category 1 [12] | 1929 | Tropical depression | June 30, 1929 |
Unnamed [13] | Unknown | 1935 | Tropical storm | August 22, 1935 |
Unnamed [14] | Tropical storm [15] | 1951 | Tropical storm | August 3, 1951 |
Unnamed [14] | Category 1 [15] | 1958 | Tropical storm | October 6, 1958 |
Claudia [9] | Tropical storm [15] | 1962 | Tropical storm | September 25, 1962 |
Tillie [13] | Tropical storm [15] | 1964 | Remnant low | September 9, 1964 |
Emily [14] | Category 1 [15] | 1965 | Remnant low | September 6, 1965 |
Kirsten [16] | Tropical storm [15] | 1966 | Remnant low | September 29, 1966 |
Katrina [9] | Category 1 [15] | 1967 | Tropical storm | August 29, 1967 |
Hyacinth [14] | Tropical storm [15] | 1968 | Tropical depression | August 20, 1968 |
Pauline [17] | Category 1 [15] | 1968 | Remnant low | October 3, 1968 |
Norma [9] | Tropical storm [15] | 1970 | Remnant low | September 4, 1970 |
Irene-Olivia [18] | Category 3 [15] | 1971 | Remnant low | October 1, 1971 |
Joanne [9] | Category 2 [15] | 1972 | Tropical storm | October 4, 1972 |
Kathleen [9] | Category 1 [15] | 1976 | Tropical storm | September 10, 1976 |
Liza [5] | Category 4 [15] | 1976 | Remnant low | October 2, 1976 |
Doreen [9] | Category 1 [15] | 1977 | Tropical storm | August 13, 1977 |
Heather [9] | Category 1 [15] | 1977 | Tropical depression | October 4, 1977 |
Octave [9] | Tropical storm [15] | 1983 | Tropical storm | September 28, 1983 |
Norbert [19] | Category 4 [15] | 1984 | Tropical depression | September 25, 1984 |
Polo [20] | Category 3 [15] | 1984 | Remnant low | October 3, 1984 |
Raymond [14] | Category 3 [15] | 1989 | Tropical depression | October 5, 1989 |
Boris [21] | Category 1 [15] | 1990 | Remnant low [21] | June 11, 1990 |
Lester [14] | Category 1 [22] | 1992 | Tropical storm | August 22, 1992 |
Hilary [23] | Category 3 [15] | 1993 | Remnant low | August 27, 1993 |
Flossie [24] | Category 1 [15] | 1995 | Remnant low | August 11, 1995 |
Ismael [14] | Category 1 [15] | 1995 | Remnant low | September 15, 1995 |
Nora [9] | Category 4 [15] | 1997 | Tropical storm | September 25, 1997 |
Frank [25] | Tropical storm [15] | 1998 | Remnant low | August 9, 1998 |
Isis [26] | Category 1 [15] | 1998 | Remnant low | September 5, 1998 |
Olivia [27] | Tropical storm [15] | 2000 | Remnant low | October 11, 2000 |
Juliette [28] | Category 4 [15] | 2001 | Remnant low | October 3, 2001 |
Ignacio [29] | Category 2 [15] | 2003 | Remnant low | August 25, 2003 |
Marty [14] | Category 2 [15] | 2003 | Remnant low | September 22, 2003 |
Javier [30] | Category 4 [15] | 2004 | Remnant low | September 20, 2004 |
Emilia [31] | Tropical storm [15] | 2006 | Remnant low | July 25, 2006 |
John [32] | Category 4 [15] | 2006 | Remnant low | September 5, 2006 |
Henriette [33] | Category 1 [15] | 2007 | Remnant low | September 6, 2007 |
Dolly [5] | Category 2 [15] | 2008 | Remnant low | July 28, 2008 |
Julio [34] | Tropical storm [15] | 2008 | Remnant low | August 25, 2008 |
Jimena [35] | Category 4 [15] | 2009 | Remnant low | September 5, 2009 |
Norbert [36] | Category 3 [37] | 2014 | Remnant low | September 8, 2014 |
Odile [38] | Category 4 [39] | 2014 | Remnant low | September 17, 2014 |
Newton [40] | Category 1 [41] | 2016 | Remnant low | September 7, 2016 |
Rosa [42] | Category 4 [43] | 2018 | Tropical depression | October 2, 2018 |
Sergio | Category 4 | 2018 | Tropical depression | October 13, 2018 |
Hilary [44] | Category 4 | 2023 | Remnant low | August 20, 2023 |
Records of tropical cyclones in the East Pacific before 1950 are sparse, but there were still several storms that produced rainfall over Arizona in this period.
The 1980s saw destructive tropical cyclones pass through the state, as was the case with the previous decade.
During the 1990s, several tropical systems affected Arizona even after losing all tropical characteristics. However, two hurricanes survived long enough to reach Arizona while still considered tropical systems.
The last decade saw no storms reach Arizona while retaining tropical characteristics; however, numerous remnant lows caused heavy rainfall and flooding throughout the state.
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