Atlantic Hurricane Season Quiet

October 27, 2:42 PMDC Weather ExaminerScott Sumner

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This is a view of the current El Nino / La Nina evolving in the tropical Pacific Ocean. You are looking westward, across the equator in the Pacific Ocean, from a vantage point somewhere in the Andes Mountains in South America. The colored surfaces show TAO/TRITON ocean temperatures. The top surface is the sea-surface, from 8°N to 8°S and from 137°E to 95°W. The shape of the sea surface is determined by TAO/TRITON Dynamic Height data. The wide vertical surface is at 8°S and extends to 500 meters depth.

TAO/PMEL/NOAA

With the presence of an El Nino in the Pacific Ocean, the tropics have been fairly quiet in the Atlantic, as only one named storm (Claudette), to this point, has reached land. With only a little over a month to go before the official end to hurricane season, there have been a total of eight named storms, two hurricanes (both major) and two tropical depressions. Those numbers, to this point, are near to slightly below what was predicted by NOAA and Dr. William Gray at Colorado State University, as the former predicted: Named storms: 9-14 Hurricanes: 4-7 Major hurricanes: 1-3 and the latter predicting: Named storms: 12 Hurricanes: 6 Major hurricanes: 2. To see the tracks of all the storms so far click here.

The feeling with some scientists, is that part of the reason for the slight decline in tropical cyclone activity,relates to the presence of a El Nino in the Western Pacific. Gerry Bell, lead seasonal hurricane forecaster for the National Weather Service's Climate Prediction Center, is one that feels that way. He says in a online article by Russell McLendon, that "Upper-level winds from the west come across the Caribbean Sea, produce increased wind shear, and that's what hinders hurricane activity. El Niño is so large, and the tropical Pacific is just right there across Mexico, so it's not a far distance, actually." Mr. Bell goes on to say, "El Niño is not the only climate player in the game," Bell says. "For the Atlantic and Pacific, [hurricane] activity is strongly affected by tropical climate patterns that can last for decades at a time. That includes warmer water across the tropical Atlantic, and stronger monsoonal rains and low-pressure systems coming off of Africa. That really sets the stage for more activity."

Looking back at the seasonal archives during El Nino/La Nina years, I noted a few things...1.)When the Pacific has an active hurricane season, usually the opposite is true for the Atlantic Basin. 2.) During El Nino years, even if many storms form, a small percentage of storms make landfall and 3.) During La Nina years, when the Atlantic is generally more active, the activity lasts well beyond the typical seasonal peak (Early Sept. to Mid October). To verify those statements above, I have made a chart comparing El Nino/La Nina seasons and this is what I found:

EL NINO Seasons:
Year        # of Pacific Cyclones         # of Atlantic Cyclones
1925                    13                              4 ( 2 made landfall )
1957                    13                              8 ( 5 made landfall )
1972*                  20                              7 ( 3 made landfall )
1976                    19                             10 (4 made landfall )
1977                    17                               6 ( 1 made landfall )
1982*                  30                                6 ( 2 made landfall )
1986                    26                                6 ( 2 made landfall )
1987                    21                                7 ( 2 made landfall )
1990                    26                              14 ( 1 made landfall )
1991*                  16                                8 ( 1 made landfall )
1993                    18                                8 ( 1 made landfall )
1997*                  24                                8 ( 1 made landfall )
2006                    19                               10 ( 3 made landfall )

*Strong EL NINO Years... 5 out of 13 yrs. NO tropical cyclone formation later than 10/26

LA NINA Seasons:
Year        # of Pacific Cyclones         # of Atlantic Cyclones
1933                     0                     21 ( 2 storms active past 10/26)
1949                     0                     13 ( 1 storm active past 10/26 )
1955*                    6                    12
1964                     5                     12 (1 storm active past 10/26 )
1973*                  12                     8 (1 storm active past 10/26 )
1975*                  17                     9 ( 1 storm active past 10/26 )
1978                    23                    12 ( 1 storm active past 10/26 )
1988*                  23                    12 ( 1 storm active past 10/26 )
1995                    11                    19 ( 1 storm active past 10/26 )
1998                    16                    14 ( 2 storms active past 10/26 )
1999                    14                    12 ( 2 storms active past 10/26 )
2000                    21                    15 ( 1 storm active past 10/26 )
2007                    15                    15 ( 2 storms active past 10/26 )

* Strong LA NINA Years... 12 out of 13 yrs. listed above, tropical development or formation began near or past late October. (i.e. 1998-Hurr. Nicole 11/24-12/2; 1975 Subtropical Storm #2 12/9-12/13; 2007- T.S. Olga 12/10-12/16)

Recent data collected by NOAA's Climate Prediction Center indicates that El Nino has strengthened to moderate levels, but the monthly average Sea Surface Temperatures will have to remain above 1.0°C for five consecutive months in order for this to be considered a "moderate" El Niño event. Regardless, the ongoing intensification of El Niño could help keep the rest of hurricane season in the Atlantic Basin in check and at a minimum.

For further interesting reading and nice graphics look at this website and this animation.