Tephigram airmass analysis comparisons


On October 7, 2004, the PASPC-Winnipeg released a radiosonde at 19Z to gauge the potential for thunderstorms to develop. (None did.)

Overlaying the tephigram from that launch, however, revealed how remarkably similar the airmass in Winnipeg was to that in Bismarck, ND, 7 hours prior.

Tephigram analysis (or, in the United States, skew-T diagram analysis) allows meteorologists to gauge many things--among them are the thunderstorm potential, freezing rain potential, cloud layers, icing potential (for aviation use), and airmass analysis to help with frontal analysis.

The tephigrams presented here are, in order, Winnipeg (XWI), Bismarck (BIS), both XWI (black) and BIS (red), and XWI and the GEM regional forecast tephigram valid at the same time.

Of note here are two things. First, Winnipeg and Bismarck are obviously in the same airmass. The wet bulb temperature--the dashed line on each plot--is the best indicator of the airmass being observed.

Also of note is something the forecasters tend to see a lot, especially during the summer convective season: the model (in this case, the GEM regional) tends to undrestimate the warmth of a warm layer ("cap") above the surface, usually around 850 mb. In this case the GEM was too cool by 2 degrees at 850 mb.

To see the tephigrams, click here.

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Last update to this page: October 8, 2004