Hurricane Karen? Wait a Few Months

It has been a very disturbed -- and yet not all that active -- September in the Atlantic region for hurricanes. Disturbed, in the sense that the hurricane watchers have been tracking quite a number cloud clusters with the potential for development into dangerous storms. And yet relatively quiet in the sense that few of these disturbances have actually developed -- certainly not into strong hurricanes.

There are a few more disturbances out there right now that may or may not get actual storm names soon enough. I suspect we'll have our "L" storm before long, perhaps as early as later today if a disturbance currently being called Tropical Depression 13 develops as expected in the southwestern Gulf of Mexico/Bay of Campeche area.

But meanwhile, we just had our fourth named hurricane of the year ... um, maybe. Definitely not for very long. In last night's 11 p.m. ET update on Tropical Storm Karen, forecaster Eric Blake put it like this:

THE MAXIMUM FLIGHT LEVEL WIND REPORTED WAS 69 KT ... WITH A PEAK SURFACE VALUE OF 62 KT REPORTED TWICE ... NOT QUITE HURRICANE STRENGTH. HOWEVER ... GIVEN THE DEGRADED SATELLITE APPEARANCE FROM EARLIER TODAY ... KAREN WAS ALMOST CERTAINLY A HURRICANE THEN ... AND THIS LIKELIHOOD MAY BE REFLECTED IN THE FINAL BEST TRACK FOR THE SYSTEM. AT THIS TIME ... THE INITIAL INTENSITY IS HELD AT 60 KT FOR THIS ADVISORY.

Sounds a bit technical -- what does this mean?

Essentially, Karen put on a burst of intensification yesterday, but has now weakened again as the storm is being affected by strong wind shear. What Blake is saying is that probably, Karen briefly became a weak hurricane -- sustained winds of 65 knots or higher -- before weakening began. When the National Hurricane Center does its customary late- or post-season report on Karen, it sounds like Blake thinks they'll upgrade the storm to hurricane status. Maybe.

What this got me thinking is: Well, at least the National Hurricane Center does a systematic post-season reanalysis to determine, as best they can, how strong a given storm actually was. But I track storms in all parts of the world, and so far as I can tell, in other regions such reanalysis is not done in nearly such a comprehensive way as it's done for storms in the Atlantic.

That becomes very problematic when you're trying to determine how many Category 4 and 5 storms there are in a given year -- what do you do with borderline Category 3/4 storms that might, if they'd occurred in the Atlantic and been reanalyzed by the National Hurricane Center, have been upgraded to Category 4? I would argue that both Cyclone George and Cyclone Jaya of this year would fall into that category. The Australian Bureau of Meteorology is apparently planning to reanalyze George. I don't know what's happening with Jaya, if anything.

It's just another indicator of just how hard it is to accurately measure hurricanes, typhoons, and cyclones in various parts of the world -- and how continuing data difficulties make generalizations about global trends in storm behavior exceedingly difficult to make.