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Global Tropical Cyclone Activity remains at 30-year lows at least. The last 24-months of ACE at 1090 represents a decrease from the previous months and a return to the levels of September 2009. Since Hurricane Katrina (August 2005) and the publication of high-profile papers in Nature and Science, global tropical cyclone ACE has collapsed in half. This continues the now 4-consecutive years global crash in tropical cyclone activity. While the Atlantic on average makes up about 10% of the global, yearly hurricane activity, the other 90% deserves attention and has been significantly depressed since 2007. See Figure below.

Northern Hemisphere year-to-date ACE is nearing 50% below normal. The Western North Pacific is at 17% of normal (or the past 30-year average).

August 8: Current 7-10 day forecast models see little if any tropical activity on the horizon.

Colin and Bonnie both go into the books as a couple of the weakest tropical cyclones on record. No storms were recorded in the Eastern Pacific during July! August and September will have to be record activity for the hurricane forecasts to pan out in the North Atlantic. (See discussion at Watts Up With That?)

July 31: Current ACE for July in the Northern Hemisphere is 14.2 and consists of Alex, Chanson, Bonnie, and Chanthu. No ACE was recorded in the Eastern Pacific.


Figure: Global and Northern Hemisphere Accumulated Cyclone Energy: 24 month running sum through July 31, 2010. Note that the year indicated represents the value of ACE through the previous 24-months for the Northern Hemisphere (bottom line/gray boxes) and the entire global (top line/lime green boxes). The area in between represents the Southern Hemisphere total ACE.

Note: Southern Hemisphere tropical cyclone data is spotty prior to the introduction of reliable satellite monitoring, thus the ACE represented at the beginning of the 1980s is likely underestimated due to missing data. Thus, it is possible that the current global collapse in TC ACE is comparable to lows experienced prior to 30-years ago.

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