Thursday, December 15, 2005

Atmospheric Tug of War

Not much new I can add to my post yesterday. However, given the cold air surge across the South China Sea, large-scale baroclinic development across the north Pacific Ocean and anomalously warm SSTs in the regions of the equatorial date line and south Pacific, I am concerned that a good portion of the tropical convective forcing may shift quickly east during the next week or so. I have been caught by these types of events before, and in this case the extratropics may now be forcing the tropics.

Nearly all global models indicate a split flow like structure across North America by late next week, with an extended jet across the north Pacific. I do go along with that, particularly if a convective signal propagates into the western hemisphere (which models initially will not capture well). We would see a SDM Stage 3 response, inspite of low global AAM.

At this point, in addition to diligent monitoring of both the models and atmosphere, we also need to pay close attention to circulation impacts due to the seasonal cycle. This includes the tropical convective forcing moving south of the equator and onset of the Australian monsoon by around the end of this month. Perhaps we will see SDM Stage 3 for much of the rest of this month followed by a transition to Stage 1 during the first 1-2 weeks in January. Interestingly it is not uncommon to see a winter storm across the Rockies and Plains during that time.

Other than a period of below normal temperatures with some light snowfall/freezing drizzle this weekend, the weather across southwest Kansas for at least the next 10 days looks generally uneventful. Temperatures should warm to above normal by late next week, and may stay that way until next year.

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