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What Has Made This Hurricane Season Remarkable So Far
Published: September 13, 2017
The 2017 Atlantic hurricane season has been exceptionally busy with several remarkable and record-breaking events.
(MORE: Hurricane Central)
Through Sept. 12, there have been 11 named storms, 6 hurricanes and 3 major hurricanes (Category 3 or higher). This is well-above average, given the 30-year average for the entire season is 12 named storms, 6 hurricanes and 3 major hurricanes.
Here's a look at several of the most noteworthy occurrences we've seen so far this season.
Harvey's Incredible Rainfall
Hurricane Harvey was a historic storm that was the first major hurricane to make landfall in the U.S. since Wilma in 2005. Harvey made landfall on Aug. 25 near Rockport, Texas, with maximum sustained winds at 130 mph, making it a Category 4 hurricane.
(MORE: Hurricane Harvey Recap)
Harvey then moved extremely slowly from Aug. 26-30, resulting in extreme rainfall over southeastern Texas and southwestern Louisiana.
The areal coverage of locations receiving at least 20 inches of rainfall was larger than West Virginia.
The top rainfall total was a preliminary 51.88 inches at Cedar Bayou near Highlands, Texas, which will become the new record for greatest rainfall total from a tropical cyclone in the Lower 48 when confirmed. The previous record was 48 inches in Medina, Texas during Tropical Storm Amelia in 1978.
This amount of rainfall in a short period of time brought devastating flooding to the region, including Houston.
Irma's Record-Breaking Winds
Hurricane Irma was an incredibly powerful and destructive storm that broke many records.
(MORE: Irma's Notable Extremes)
Irma's maximum sustained winds were at 185 mph for 37 hours, setting a new record for length of time a tropical cyclone maintained winds of that strength anywhere in the world, according to Dr. Phil Klotzbach, a tropical scientist at Colorado State University. The previous record was 24 hours set by Typhoon Haiyan in 2013.
Irma is one of only four hurricanes with at least 185 mph winds in the Atlantic on record. The other three are Wilma (2005), Gilbert (1988) and Allen (1980).
Hurricane Irma is also the strongest storm on record to exist in the Atlantic Ocean, outside of the Caribbean and Gulf of Mexico.
Irma is also the strongest storm on record to impact the Leeward Islands, where catastrophic damage has been reported.
Two Category 4 Atlantic Hurricane Landfalls in the U.S. in One Year
Harvey and Irma both made landfall in the U.S. as Category 4 hurricanes, marking the first time since 1851 that this has occurred in the Atlantic.
Hurricane Harvey made landfall in Texas on Aug. 25, with maximum sustained winds of 130 mph and Hurricane Irma made landfall in the Florida Keys on Sept. 10 with maximum sustained winds of 130 mph, as well.
In general, Category 4 or 5 hurricane landfalls are rare in the U.S., with only 27 on record. Therefore, it is quite remarkable that two such landfalls took place in the U.S. in the same year.
This, however, has taken place when the Pacific basin is included. In 1992, Hurricane Andrew made landfall in South Florida as a Category 5 hurricane and Hurricane Iniki make landfall as a Category 4 on Hawaii's Kauai Island.
Two Atlantic Hurricanes With Winds of 150 mph At Same Time
On Sept. 8, 2017, both Hurricane Irma and Hurricane Jose had maximum sustained winds of at least 150 mph. This was the first time on record that this has been observed in the Atlantic basin.
Hurricane Irma had maximum sustained winds vary between 150 and 160 mph on Sept. 8, making it a very powerful storm.
Hurricane Jose was also in a favorable environment and strengthened on Sept. 8. Data from an Air Force Hurricane Hunter plane indicated that maximum sustained winds had reached 150 mph by late morning. Jose continued to strengthen and reached 155 mph that night, before weakening slightly to 145 mph on the morning of Sept. 9.
Three Consecutive Atlantic Named Storms Reached Category 4
Late August into September is the peak of hurricane season and this year is proving to be no exception. The favorable environmental conditions, including low wind shear and high oceanic heat, allowed Harvey, Irma and Jose to all intensify into powerful hurricanes.
According to Klotzbach, this was the first time on record that three consecutive Atlantic named storms reached Category 4 status or higher.
Before Harvey, Hurricane Gert became the first Category 2 hurricane of the season on Aug. 16. After Jose, Hurricane Katia also reached Category 2 status Sept. 8 and made landfall in eastern Mexico with maximum sustained winds of 75 mph.
Impressive Rapid Intensification Periods
(Satellite data is GOES-16 Experimental)
Rapid intensification happens when a tropical cyclone increases its maximum sustained winds by at least 35 mph in 24 hours or less.
Hurricane Harvey underwent rapid intensification from late Aug. 23 into Aug. 24. During that time, Harvey's maximum sustained winds increased by 45 mph, going from a tropical depression with winds of 35 mph to a hurricane with winds of 80 mph. Harvey continued to strengthen, reaching Category 4 status, with maximum sustained winds of 130 mph on Aug. 25.
Hurricane Irma also experienced an amazing period of rapid intensification. Irma was a tropical storm with maximum sustained winds of 70 mph early on Aug. 31 and became a major hurricane with maximum sustained winds of 115 mph just 12 hours later. Irma continue to intensify and its maximum sustained winds reached 185 mph on Sept. 5.
Hurricane Jose also rapidly intensified. Jose had maximum sustained winds of 120 mph early Sept. 8 and by that night maximum sustained winds topped 155 mph, meeting the criteria for rapid intensification.
Bret's Strange Formation
Tropical Storm Bret developed June 19 in the main development region (MDR) of the tropical Atlantic. This is a common area for development, but not usually until August.
The formation of Bret marked the earliest a storm has formed in the MDR, breaking the previous record set on June 22, 1979, by Tropical Storm Ana.
(MORE: Tropical Storm Bret Recap)
Bret is also only the third known tropical storm to develop in the MDR before July 1.
Tropical systems tend to develop in June in the Gulf of Mexico, northwestern Caribbean or Southeast coast, which is shown in the graphic above.
Arlene's Rare April Appearance
(National Hurricane Center)
Tropical Storm Arlene was only the second April Atlantic tropical storm in the satellite era. The other such occurrence was Tropical Storm Ana in 2003.
Arlene was first designated Subtropical Depression One by the National Hurricane Center on April 19 and became Tropical Storm Arlene on April 20.
Arlene did not impact land, as it tracked through the central Atlantic Ocean.
In addition, Arlene is also the farthest north a tropical storm has formed in the Atlantic so early in the season.
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