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Forecaster Temp

September 2nd, 2010 admin No comments

Forecaster Temp
how do you find what level of the atmosphere is mixing to determine a surface hi temp?

When I read forecast discussions, I always read things like “this sounding is only showing mixing to the 925mb level, so therefore max temps will likely not get as high as what was thoughts yesterday…” So how can I find for myself this “mixing area” so i can forecast a max temp using this method?? Please i only need answereres from actual forecasters or weather professors, just someone who knows their shit when it comes to weather. thanx!

Yes, you will need to get a plotted balloon sounding or a forecast model sounding. I will assume you know how to use a sounding chart like a Skew T, Log P chart. (If you don’t, then my answer won’t help you. It is too just complex to explain it here on Yahoo Answers).

To find out what the estimated afternoon high temperature will be using “the air mixed down to the surface method”, you will need the latest balloon sounding or an afternoon model forecast sounding. In most cases during the warm season, you can use the standard 850 mb pressure level height as your maximum mixing height.

Follow the temperature plot up to the 850 mb pressure level. Note where the plotted temperature intersects with the 850 mb line. From that point, move down the chart by following the dry adiabat line down to the surface. The temperature at the surface will be your estimated afternoon high.

However, some days you will find an inversion (also known as a “cap”) or some kind of other air mass boundary located between the 850 mb and the surface. This layer or boundary may be strong (stable) enough to prevent the air from below to mix past above that level.

So from your example from your question, the forecaster likely looked at a sounding chart and saw a strong inversion located near the 925 mb pressure level. So he only mixed the air up to the 925 level to base his high temperature forecast for that day.