Watts Up With That? 
Aug 9, 2010
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…
Global TC 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).
- A d v e r t i s e m e n t
Figure: Northern Hemisphere cumulative ACE per day of year from July – December. See legend for appropriate axis of each basin or NH total.
Climatological yearly ACE and HDAYS are based upon 1980-2009 values (last 30 years)
Daily Cumulative ACE file 
[Month, Day, IO, EPAC, NATL, WPAC, NH]
Steve Goddard has done some interesting work that complements what Dr. Maue has discussed, see below. – Anthony
Steve Goddard writes:
Everyone in the hurricane forecast business predicted a big season this year. NOAA reaffirmed their position this week, as reported on WUWT .
One of the main reasons cited for the forecasts was “record high Atlantic SSTs.” So let’s look at the SST anomalies  in the region between the Cape Verde Islands and the US. That is the normal hurricane formation track.
SSTs have plummeted and are now not much above normal. Compare SST anomalies vs those in late May. The hurricane breeding ground has not kept it’s unusual warmth.
Has this affected hurricane formation? Circumstantial evidence suggests yes. Hurricane numbers are average , and ACE is well below average .