2008 Northern Hemisphere Tropical Cyclone Year in Review: Record Inactivity Continues
Total of 63 Tropical Cyclones during 2008 (maximum intensity reached): 35 Tropical Storm, 7 Category 1, 8 Category 2, 2 Category 3, 10 Category 4, and 1 Category 5.
USA Today Article on Northern Hemisphere Tropical Cyclone Inactivity
Flashback: 2007 Record Hemispheric Tropical Cyclone Inactivity
Where have the Northern Hemisphere Tropical Cyclones gone the last 2 years?
Upon examination of all tropical cyclone activity in the basins throughout the Northern Hemisphere for the past 2 years, a remarkable downward trend in cyclone energy has continued and reached historic levels of inactivity. Even though North Atlantic hurricane activity was expectedly above normal in 2008, the Western and Eastern Pacific basins produced considerably fewer (and weaker) than normal typhoons and hurricanes, respectively in 2008. The image below shows the previous three decades of cyclone energy (as measured by the ACE, a popular metric of climatologists used to measure hurricane energy) for all global ocean basins combined (green) and for the Northern Hemisphere (blue). Using a 24-month running sum, we see that Northern Hemisphere ACE remains at historical lows. Moreover, there has only been 1 Category 5 typhoon (Jangmi) during the past year. This cyclone activity is consistent with continued colder conditions in the Pacific Ocean and the previous strong La Nina last spring.
Left Global and Northern Hemisphere Accumulated Cyclone Energy: 24 month running sum through December 31, 2008. Note that the year indicated represents
the value of ACE through the previous 24-months.
Middle: Northern Hemisphere Monthly ACE values for the past 6 years with yearly values included. 2004 saw over twice the activity as 2007.
Right: Global Tropical Cyclone Monthly ACE values for the past 6 years with calendar year values included. Best track provided by the NHC and JTWC.
Preliminary track values included for 2008 and are not official until the respective centers complete post-season best track analysis.
Analysis of integrated global hurricane activity shows that the previous 12-24 months exemplify a continuing decreasing trend since 1997. Since tropical
cyclones occur planetwide throughout the calendar, running sums of cyclone energy are used to show the global nature of earth's cyclone energy.
Northern Hemisphere climatology: daily expected ACE.
95 3.61 100 4.0 105 4.41 110 4.84 115 5.29 120 5.76 125 6.25 130 6.76 135 7.29 140 7.84 145 8.41 150 9.00 155 9.61 160 10.24
One day at 100 kts = 8 days at 35 kts --- One day at 135 kts = 4.3 days at 65 kts
Review: 2007 Tropical Cyclone Activity
During 2007, the Northern Hemisphere as a whole experienced the lowest ACE hurricane energy & number of hurricane days since 1977. 2007 was the 4th slowest year in the past half-century (since 1958)...Maue, R.N., 2009: Northern Hemisphere Tropical Cyclone Activity (in press: paper PDF).