NCHurricane2009's Blog

SLAP to 2009 Atlantic Hurricane Season Forecast!

By: NCHurricane2009, 2:52 AM GMT on October 07, 2009

I guess I got the answer to the blog post I made just two days ago (Early End to the 2009 Atlantic Hurricane Season?). The answer was blatant NO! However, in the forecast in the last blog and a blog post I made on September 15 (Trends in the 2009 Atlantic Hurricane Season), I expected a possible 1 or 2 more storms for October and November of EXTRATROPICAL origin, the type of storms like Tropical Storm Grace. For the remainder of the season thus, we may see 1 more tropical cyclone that is of EXTRATROPICAL origin.

Where I got my forecast wrong was with Henri, which developed from a tropical wave. Honestly, I was not expecting any October or November storms to develop from tropical waves due to major upper trough suppression and loads of wind shear as we typically see in the closeout of an El Nino season. What happened with Henri? The pre-Henri tropical wave came off of Africa on September 30, and looked quiet robust and persistent. Plus, it got help from a low-latitude 200 mb anticyclone off of Africa that helped its outflow & protected if from shear. But now, Henri is moving into the vast westerly wind shear regime, which is keeping it disorganized. Its forecast that Henri won't even make it past 5 days due to the shear. However, the thing to watch with Henri is beyond 5 days, it may find itself under a favorable deep-layered anticyclone that is right now spreading into the Gulf of Mexico and western Caribbean (by the way, was also not expecting there to be an impressive deep-layered ridge by this time either).

As far as the tropical latitudes go for the rest of the season, I haven't yet seen any impressive waves rolling off of Africa behind Henri (and tropical waves start dying down this time of year). It will also be key to watch how persistent the 200 mb anticyclones in the western Carribean/Gulf of Mexico and off of Africa persist/evolve (again, I personally was not expecting those features as I thought upper troughs were going to dominate late season due to El Nino). If anyone has insight or feedback as to why those recent anticyclones have developed, particularly the massive one in the western Caribbean/Gulf of Mexico, that would be awesome.

Satellite image of Tropical Storm Henri

Regardless of any predictions made, everyone should always be prepared.

**Special Closing Notes**
1) In recent years, storms like Grace are challenging the way we think of tropical cyclone formation. I will have a post on this later this week.

2) If you try to view the archives of this blog but get an error message "ERROR: It appears this user does not have a WunderBlog," try accessing the archives through this link:

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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