Posted by: pyeager | September 16, 2009

California Heat, Fire Danger–Global Warming?

There are many good resources for local forecast information, so I usually focus on larger scale items in this blog; however, local forecast information and larger scale items sometimes merge. I suspect that will be the case with California weather over the next week or two since I expect that the hot, dry weather pattern will result in talk about global warming.

Hot Weather on the Way

It’s been a long time since I’ve posted a weather forecast chart, but here goes–this map is a forecast of what the upper levels of the atmosphere will look like in one week, on September 23:

Forecast map valid September 23, 2009; courtesy of NOAA

Forecast map valid September 23, 2009; courtesy of NOAA

California Heat

The combination of the strong upper-level high pressure system (shown above) and an offshore flow (not shown), which means air blowing from the land toward the ocean, will result in hot and dry weather in California (and much of the West). Without getting into too many forecasting details, it’s likely that the weather will turn hot even in areas close to the coast, such as the Bay Area, the Central Coast, and perhaps even the beaches around Los Angeles. Some record high temperatures might even occur.

High Fire Danger

The summers are ALWAYS dry in California, so by the fall, the risk for fire danger is always there. It’s exacerbated by a weather pattern that brings hot and dry (in terms of relative humidity, not lack of precipitation) weather, especially if it’s accompanied by a gusty offshore wind. This type of weather typically occurs at least once during the fall (more accurately, from the late summer through early winter), setting the stage is set for a heightened risk of wild fires. It’s the nature of California weather.

Is It a Reflection of Global Warming?

My answer in one word is NO.

The weather pattern is not unsual enough for me to make any such statement. The weather pattern is, indeed, dramatic, but it’s dramatic in a way that is well within the normal range of weather patterns. Chilly San Francisco has had 19 record high temperatures of 94 degrees or higher, including 8 records of 100 or higher, during the month of September, and it’s not because a pattern such as this is unusual.

This type of hot weather, and the increased fire danger associated with the weather pattern, is common in California.

Global Warming Disclaimer

It’s not that I don’t believe that man might be contributing to global warming, but the only way we will accurately make such a determination is through reasonable discussion, not the assumption that any hot weather or dramatic weather is proof of global warming. And I say that as someone who is not on the political side that typically is associated with global warming denial; I’m a meteorologist who doesn’t like normal weather patterns being portrayed as abnormal.

–Paul Yeager


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