Was Karen A Hurricane?

I stopped by the National Hurricane Center (NHC) to visit some friends on Wednesday night on the way home from Local 10.

The NHC Hurricane Specialists were writing advisories on Tropical Storm Karen over the tropical Atlantic about 1,000 miles east of the Windward Islands and on Tropical Depression Thirteen over the southwest Gulf of Mexico (which would eventually become Hurricane Lorenzo).

While I was at the NHC, a NOAA Hurricane Hunter plane was flying Tropical Storm Karen. Normally, aircraft reconnaissance planes are not sent on operational missions this far from land. But this was primarily a research flight tasked with collecting data for the new NOAA Hurricane WeatherResearch and Forecast (HWRF) model. The intent is for the Hurricane Hunter to collect data in the core of the hurricane to use in the HWRF model to improve intensity forecasting. While I was at the NHC, the NOAA plane sent in a couple of reports of 71 mph surface winds in Tropical Storm Karen. It takes 74 mph sustained winds at the surface to be designated a hurricane.

These surface winds were measured from the Stepped Frequency Microwave Radiometer (see my August 7th blog). The cloud pattern in satellite imagery was actually degraded in appearance by the time the plane got there, implying that Karen had been stronger before the arrival of the aircraft. The NHC advisory reported Karen&#! 8217;s maximum winds of 70 mph in the next forecast cycle, but mention ed in the discussion that “Karen was almost certainly a hurricane” earlier in the day. The NHC always does a post analysis of all storms and hurricanes, and Karen may well be upgraded to hurricane status on post analysis. This was mentioned in the Tropical Cyclone Advisory issued by the NHC on the evening of Sept. 26, and there should be no surprise if NHC upgrades Karen to a hurricane after the fact.

So why bother? Because the NHC wants to get the climatology right. There are a number of articles on the increasing numbers of hurricanes due to global warming and/or natural cycles. If Karen is deemed to be a hurricane by the NHC after the fact once all the data is examined, so be it. I’ll share more about the quality of historical hurricane databases in a future blog.


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