Hurricane Kenneth breaks a record for the eastern Pacific

Hurricane Kenneth, the 11th named storm of the 2011 eastern Pacific hurricane season, formed on November 19, 2011. It went on to become the strongest known hurricane to form this late in the season in the eastern Pacific. Kenneth had almost perfect conditions such as low wind shear, favorable atmosphere in front of it, and sea surface temperatures warm enough to enable a tropical system to become a major hurricane.  A major hurricane is classified as a storm with a Category 3 or higher rating with winds over 111 miles per hour. Kenneth became a strong Category 4 storm with 145 mph winds, making Kenneth the latest major hurricane ever to form in the eastern Pacific Ocean.

The eastern Pacific and the Atlantic hurricane seasons end on November 30.  Tropical systems rarely form in the month of November in the eastern Pacific.  The hurricane that held the previous record of the strongest cyclone so late in the season was recorded back in December 5, 1983 when Hurricane Winnie was a Category 1 storm with maximum sustained winds of 90 mph.

The ocean content in the eastern Pacific is not incredibly warm, which is what makes Kenneth so extraordinary in its significant intensification.  There are very few areas in the eastern Pacific that have deep areas of warm ocean waters that could aid in tropical development.  In the map below, yellow and orange colors show very warm temperatures.

The eastern Pacific hurricane season has been extremely unusual. Out of the 11 named storms, 10 became hurricanes.  Out of the 10 hurricanes, six of them became major hurricanes.  Here is a list of the 10 hurricanes with their maximum wind speeds for the 2011 eastern Pacific hurricane season:
1) Hurricane Adrian – 140 mph (MAJOR)

2) Hurricane Beatriz – 90 mph

3) Hurricane Calvin – 80 mph

4) Hurricane Dora – 155 mph (MAJOR)

5) Hurricane Eugene – 140 mph (MAJOR)

6) Hurricane Greg – 85 mph

7) Hurricane Hilary – 145 mph (MAJOR)

8 ) Hurricane Jova – 125 mph (MAJOR)

9) Hurricane Irwin – 90 mph

10) Hurricane Kenneth – 145 mph (MAJOR)

As of now, Hurricane Kenneth has 90 mph winds and is forecast to weaken and dissipate by the end of the week as it moves out into the cool open waters of the Pacific ocean.  Kenneth is not likely to harm anyone, but some of the models show that some of its tropical moisture could be pulled into the southwest United States as the next large system develops this weekend across the central and eastern United States.

Bottom line:  Hurricane Kenneth became the strongest known hurricane to form this late in the season in the eastern Pacific.  The storm was very symmetric with a large, defined eyewall which indicated a strong hurricane. Dr. Jeff Masters has posted that Kenneth could be classified as an annular hurricane, meaning it contains few spiral bands and a very thick eyewall.  Only 4 percent of hurricanes are annular, and they are typically stronger storms that weaken slowly. The eastern Pacific 2011 hurricane season is the opposite of the 2011 Atlantic hurricane season.  It had quality instead of quantity.  Many storms were relatively strong in the eastern Pacific, with 10 out of 11 becoming hurricanes.  In the Atlantic this year, we had a lot of named storms, but many were weak (below hurricane status).

Satellite view of Alaska’s November storm

November 23, 2011

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Matt Daniel

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