Where Have All The Typhoons Gone?

Well for those of you who don't already know it, the Western North Pacific (WPAC) is the most prolific tropical cyclone generation region in the world. The annual average climatology (1959 to 2005) of WPAC tropical cyclones is 32, of which 26 become tropical storms, with about 18 of these becoming typhoons (same as hurricanes just with a different name).

Below is a list of monthly counts of all WPAC tropical cyclones (depressions, storms and typhoons) and typhoons by month for the period 1959 to 2005 taken from the Joint Typhoon Warning Center (JTWC).

Source: https://metocph.nmci.navy.mil/jtwc/atcr/2005atcr/chapter1/chapter1.html

Note that I have highlighted average typhoon counts for October, November and December (red); on average those months see 5 to 6 typhoons form.

Now look at the 2008 tropical storm and typhoon list.

The last typhoon to form in the WPAC in 2008 did so on September 25th! Yes, I said September. Yes, we had 10 tropical storms form after September 25th, but no typhoons. Of course we have to remember that WPAC tropical cyclone season does not end until the end of December, but we are only a couple of weeks away from that point and currently there's only a weak tropical depression.

This early end to typhoon development has not happened within the tropical cyclone record from 1959 until this year! Since 1959, the fewest number of typhoons that have formed beyond September 25th was 3 in 1999. 2008 will either be a record early end and/or a year with a record low late season typhoon count. Of note also is that only 11 typhoons have formed in 2008 compared an average of 18. So this very early end has also made 2008 a year with only 61% of the average number of typhoons (so far). The number of tropical storms in 2008 is near average.

So we can find large year-to-year swings in the start and end times to tropical cyclone seasons around the world (2008 being one of them for the WPAC). Unfortunately understanding their causes remain elusive; hence we currently are unable to forecast these very anomalous events in advance!