We talked last week about a potential Hurricane Helene or Hurricane Gordon as the long range GFS and Ensemble models saw development of a Tropical wave over the Atlantic on the 10th August and genesis to Tropical storm status shortly afterwards. In fact the area of interest developed very much on program but with an decreasing chance of becoming a Tropical storm and this continues to be the case.
Working hard to balance a bit of excitement about charts showing purple blobs of long awaited swell with a grasp of the science of forecasting this sort of storm in the 14-16 day window we had, in the longer range, maintained healthy skepticism. But increasingly as the Tropical wave developed on schedule and GFS and ensemble model guidance was for a relatively high probability of a tropical storm we became more confident. The NHC suggested a 50% probability within 48hrs as the storm tracked over the Cape Verde Islands on Friday and fingers were crossed.
However, as it stands, we’ve still not seen this low amount to anything of interest. While the NHC still give it a 20% chance within the next 48hrs those odds hardly inspire confidence. The GFS model is now showing it intensifying on a route back east, hardly improving the outlook for the US East coast even if correct. The chart above looks markedly less interesting than the one issued on Friday.
So there we have it – a textbook example of confident false positive prediction of genesis if you’re a forecast geek – or simply a continuing lack of East coast Hurricane swell for everyone else. If you’re interested in a thorough (and technical) analysis of using these same models for Tropical Storm forecasting there’s an interesting paper here analyzing the 2006 season. By coincidence the NHC’s naming convention means that year featured it’s own Ernesto, Gordon and Helene.
Looking forward the outlook is a little mixed. We’re still relatively early in the season and the NHC have actually raised their forecast for named storms this year despite increasing El Nino activity (which can cause Atlantic winds disruptive to storm formation).