Monday, August 31, 2009

Re: Tropical Storms Passing South End of Baja


Just a review of my rule-of-thumb regarding Tropical Storms and Gulf of California surges.
If a storm passes through the shaded box shown above moving with a westward component, then the winds and pressure rises east and southeast of the center trigger a surge. The surge usually occurs within about 24 hours after the storm moves north of 20N.


However, if a storm is moving to the north or north-northeast the situation becomes more complicated. In this case (or if the storm actually enters the GoC) the pressure gradient can point down the GoC and the only pressure rises are behind the storm. Forecasting the weather and storms ahead of the TS becomes complicated by many factors, including MCS developments as hot, unstable air flows into the circulation from mainland Mexico; the track and speed of the TS as it decays; the strength of easterly winds north of the system; etc.



It appears that Jimena is going to be one of these tough ones to outguess. Art Douglas notes that a large MCS may develop tonight along the first rainband over the southern GoC and act to push the subtropical air rapidly up the Gulf. So we'll have to wait and watch what this powerful Hurricane does.

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