Update: Global Tropical Cyclone Energy nearing 50-year lows

Figure: Using a longer-database of hurricane tracks for the globe, the recent downturn in global TC energy is nearing record low levels of inactivity - the lowest in 50-years. Full details forthcoming. [updated June 26, 2009]
See Guest Climate Audit blog posting June 30, 2009

Global Tropical Cyclone ACE valid July 5, 2009

BASIN	2009 Current	YEARLY	Thru June 30	Thru July 31	Avg July
Northern Hemisphere	32.655	563	64.0	131.7	67.7
North Atlantic	0	106	1.4	7.6	6.3
Western Pacific	25.49	309	41.6	75.2	33.6
Eastern Pacific	2.9475	132	13.5	41.4	27.9
Northern Indian	4.22	17	7.5	7.5	0.02
Southern Hemisphere	107	229	Out of	Season	---

Tropical Cyclone ACE Update

Figure: 24-month running sum of tropical cyclone accumulated cyclone energy for the entire globe (top black squares / time series) and the Northern Hemisphere only (bottom green squares / time series). The difference between the two time series is the Southern Hemisphere total. Data is shown from June 1979 - June 29, 2009 mainly because intensity estimates of SH cyclones are often missing in the JTWC best-tracks prior to 1980. See notes.

Note: climatology is based upon the past 30-years of tropical cyclone activity (1979-2008). Historical tropical cyclone tracks are obtained from two sources: National Hurricane Center (NHC) for Eastern Pacific and North Atlantic basins and the Joint Typhoon Warning Center (JTWC) for the Western Pacific, Northern and Southern Indian Oceans, and the South Pacific including the Australian region. Best-track data when cyclones are in an extratropical phase are disregarded, where this is included in the datasets.

While there are several other sources of best-track hurricane data for the different basins around the globe, it is not apparent which source of tropical cyclone intensity estimates is the best, most correct, or most consistent throughout the past 30-years. Until that research is completed, it is my policy to use NHC and JTWC data for global tropical cyclone data. I will attempt to use RSMC (Tokyo) and the IBTrACS merged database for comparison purposes in the near future. (Update: June 24, after calculating ACE using the IBTrACS mean intensity, which can include from 1-4 different reporting centers, the differences are negligible. Therefore, it is appropriate to use the NHC+JTWC for global studies on yearly time scales. Naturally differences crop up when examining storm by storm and observation by observation differences. This is a disasterous complication when doing count/frequency studies such as Webster et al. (2005) but is mitigated with accumulated cyclone statistical studies (i.e. Emanuel 2005; Maue 2009)).

Update: Global Tropical Cyclone Energy nearing 50-year lows

Global Tropical Cyclone ACE valid July 5, 2009

Tropical Cyclone ACE Update

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