The Average Tropical Cyclone Eye Size, ROCI, and Ambient Pressure

Let’s start with the Atlantic Basin. This is from 1988-2010 Best Track for Atlantic Hurricane
1988-2010 Best Track for Atlantic Hurricane

Eye Size
Mean
23.1 Nautical Miles (nm)

Median
20 nm

Standard Deviation
10.9

Smallest
5 nm (I do not know what is up with this, but the Best Track lists Wilma’s eye as 5 nm, even though the actual size was 2 miles or 1.7 nm)
Wilma 10/19/2005 1200 UTC (Z)

Largest
90 nm
Ophelia 9/13/2005 0000Z

Ambient Pressure
Mean
1011.1 Millibars (mb)

Median
1011 mb

Standard Deviation
2.96

Lowest
988 mb
Earl 9/5/2010 0000Z

Highest
1032
Isidore 9/28/1996 0600Z

Radius of the Outer Closed Isobar (ROCI)
Mean
186.4 nm

Median
180 nm

Standard Deviation
65.1

Smallest
30 nm
Iris 9/20/1989 0000Z

Largest
555 nm
Gilbert 9/12/1988 1200Z

Here is the East Pacific, which is off the West Coast of Mexico.
For the East Pacific.

From 2001-2010 Best Track for East Pacific Hurricane
2001-2010 Best Track for East Pacific Hurricane

Eye Size
Mean
16.7 nm

Median
15 nm

Standard Deviation
8.2

Smallest
5 nm (There are probably East Pacific Hurricanes with smaller eyes.)
Juliette 9/24/2001 0600Z

Largest
75 nm
Douglas 7/24/2002 0000Z

Ambient Pressure
Mean
1009.2 mb

Median
1009 mb

Standard Deviation
1.6

Lowest
1000 mb
Blanca 6/23/2003 0000Z

Highest
1017 mb
Fausto 9/3/2002 0000Z

ROCI
Mean
166 nm

Median
160 nm

Standard Deviation
45.7

Smallest
10 nm
Blanca 6/23/2003 0000Z

Largest
340 nm
Jimena 8/31/2009 0000Z

Here is a graph for mean and median.

Mean

Median

Based on the statistics, Atlantic storms are larger than East Pacific. No surprise that the Atlantic Basin is much larger than the East Pacific Basin because there is cooler water to the west towards Hawaii. However, in El Nino years, the waters of East Pacific is more favorable, which means tropical cyclones last longer and can even travel into the Central Pacific and West Pacific as it happened with Hurricane John in 1994. The East Pacific is one of the most active basins in the world.

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