It’s not one of the sexier meteorological parameters, but some people ARE into pressure. If you have an old-style barometer, you may have noticed it’s very high today. In fact it’s the highest we’ve ever seen in December here in Portland and it’s never been higher at Astoria. Since the NWS put that image out on their FB/Twitter page, the pressure has risen to 30.80″ at PDX. The meteorological world (and most of the rest of the regular world) uses millibars though. At 10am it’s 1043.4 mb at PDX and still rising. You can see the monthly/yearly records for PDX:
So why aren’t we seeing a damaging wind event? Extreme high or low pressure doesn’t have a whole lot to do with wind speed. That’s because wind is produced by the DIFFERENCE in pressure from one spot to another. Air moves from high to low pressure so if all of the Pacific Northwest is seeing high pressure, the differences across the terrain aren’t as high as a strong high pressure to the east and low pressure to the west (to produce strong east wind for example). This time around as the strong arctic high pressure moved south out of Canada, it pretty much descended right down over the Pacific Northwest instead of sliding down mainly east of the Cascades. The pressure gradient from The Dalles to Portland is only around 6 millibars this morning…weaker than we would see in just an average east wind episode that no news media would be interested in. In fact that gradient is probably typical for about 25% of the days from late November through February here.
High temps today will end up in the mid 30s, then with a calming wind (away from the Gorge) tonight we should see widespread teens in outlying areas and near 20 in the urban areas away from the wind. Tonight and tomorrow MIGHT be our coldest nights of the winter…we’ll see.
Chief Meteorologist Mark Nelsen