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
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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)).
This page can be cited as ongoing research related to my dissertation and publications resulting from it. Maue, R. N., 2009: Northern Hemisphere Tropical Cyclone Activity. Geophys. Res. Lett., 36, L05805,
doi:10.1029/2008GL035946. Abstract
[Max Winds [kts] & ACE per storm]
The cyclone must attain 35 knot winds to have ACE counted.
Andres (65 ACE = 2.9475)
Blanca Carlos Dolores
Enrique Felicia Guillermo Hilda
Ignacio Jimena Kevin Linda Marty Nora Olaf
Patricia Rick Sandra Terry Vivian Waldo
Xina York Zelda
North Atlantic Ocean Names
TD 01(30 ACE=0.0)
Ana Bill Claudette Danny Erika
Fred Grace Henri Ida Joaquin Kate
Larry Mindy Nicholas Odette Peter
Rose Sam Teresa Victor Wanda
MAY 2009 Tropical Cyclone ACE news
The month of May saw three tropical cyclones, two in the Western Pacific, and one in the Northern Indian Ocean. All 3 reached hurricane status
with maximum sustained one-minute winds exceeding 65 knots. The total ACE was 20.3, which increases the Northern Hemisphere year-to-date ACE to 22.7.
Since Jan 1, 2009, the 5-month global ACE total is 107. Previous yearly totals are as follows: 2008 : 221, 2007 : 161, 2006 : 177, 2005 : 244.
The Southern Hemisphere cyclone season from October 2008 - April 2009 was tepid by historical standards, and one of the weakest seasons (ACE) in the past
30-years. The overall Southern Hemisphere seasonal total was also 107 (coincidentally), with a 24-month total of 296, the lowest in 20-years.