Tim Trice's Cyclone Blog

Depression developing southeast of Baja, Mexico

Posted by: timtrice, 5:28 PM GMT on September 30, 2009

The 1005mb surface low in the east Pacific, 91E, is getting its act together with great banding features and outflow to the north and west. However, convection remains inconsistent over the center of circulation (COC). Several forecast models are calling for a moderate tropical storm to track west into open waters before turning it back into Baja.

The system is still highly disorganized right now with three main areas of convection. The primary area which has been consistent longest is to the northeast of the center. The secondary area is on the northern edge of the COC and has been persistent but inconsistent throughout the day. A third minor area is located to the south and east.

Outflow is established in the north and west quadrants due to an upper-level ridge. This should continue for the next couple of days and, in addition to light upper-level shear, should further enhance convective development.

Expect considerable forecast errors with this system as some forecast models (GFDL, HWRF, CMC) take the system west before looping back towards Baja. Others (GFS) continue to take it west. These same models keep the system beneath a ridge for the first 2-3 days. It's afterwards as the ridge shifts that the models are lost in how to handle the system.

I think the GFS takes the system into slightly cooler waters, thus limiting atmospheric depth of the storm system which releases it from the steering flow of the ridge. While I don't disagree with this perception, it's very difficult to argue against the other computer forecast models.

Essentially, the forecast will depend on how deep the system gets. Should it develop fast and take advantage of the atmospheric conditions surrounding it - unlikely, but not impossible - I could easily see the GFS changing its tune. Wouldn't be the first time.

But, I'd be careful before I ruled out the GFS, also. The system is having difficulties building convection. If this trend continues and the storm system can't organize in a better fashion, I could easily see the other models coming more inline with the GFS. As seems typical this year, it really depends on how high vertically the storm develops.

Prognosis without diagnosis is malpractice.

You can follow more detailed posts on Invest 91E and other global typhoons and hurricanes on my personal hurricane website.

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I've studied hurricanes for 17 years; survived several and been amazed at all. Every storm has a story.

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