So Quiet

   For the first time in months there is not a single named tropical cyclone anywhere in the world. Sure, there have been some invest areas and one unimpressive tropical storm, but other than that, there has been nothing out there since the end of October. This is kind of strange, since the southern hemisphere basins should be more active about now, and although it is in the northern hemisphere, the northwest pacific is typically still quite active this time of year. I have some ideas why the tropics are so quiet, but each basin's reason seems to be entirely different from the others.
   In the north Atlantic, activity does begin to slow down this time of year. Right now, the specific reason is likely the fronts associated with several strong extratropical cyclones that have been moving through the northern part of the basin the past few days. Fronts are not a tropical cyclone's friend; the temperature gradients and wind shear associated with them will tear even a powerful tropical cyclone apart. The result is something like dough being fed through an extruder.
   The northeast Pacific's problem also seems to related to some rather far south mid-latitude systems. To compound the problem is the very narrow band of sea surface temperatures warm enough to fuel a tropical cyclone. This basin has a tendency for this problem since there is a very cold ocean current that runs down the pacific coast all the way from the Gulf of Alaska.
   Normally the northwest pacific should still be active right now. However, it seems like persistent heavy wind shear has suppressed development for a number of days. The sources of this shear include a very powerful sub-tropical jet that ran nearly west to east north of the Philippines and over Taiwan. Generally, I don't expect so see such strong upper-level winds so far south.
   In the Indian ocean, it is not surprising that the north Indian has seen little activity, they rarely do. As for the south Indian; many invest areas have occurred near the equator, but all seem to either lose their convection or get sheared apart altogether.
   Finally, the south pacific tends to be slow to get going, so inactivity there is the least surprising. That basin seems highly sensitive to the El Nino cycle, with some years be quiet and others being exceptionally explosive.
   Right now, the best chance for a tropical cyclone to develop is from invest 96W in the South China Sea, rather near the equator.