No, this is not some kind of meteorological pornography.
A "Dirty Ridge" is when moisture, often accompanied by clouds and precipitation, makes its way around the northern portion of a high-pressure area ( ridge is another name for high pressure).
Wet conditions with high pressure, not some type of obscenity.
Before I start, some review. Low-level winds typically rotate clockwise around higher pressure areas (see below). Thus, winds are southerly on the western side of the high and westerly (from the west) on the northern side.
You can see this windfield around the forecast high at 7 PM Friday night (below, for the 850 hPa level, about 5000 ft above the surface).
Strong winds from the southwest and west on the western and northern sides of the high draw moist air northward from the subtropics around the western flank of the high and moves it eastward over the northern flank of the storm. The clouds and rain are the "dirt" of the dirty ridge.
Fast forward to Tuesday morning (March 10), and the high is still offshore, and moisture continues to move around its western and northern flanks (see below).
This circulating moisture will be forced upward by local mountains, resulting in precipitation (the 72-h precipitation ending 5PM Sunday is shown below).
Can't believe this blog has become smutty, a shame really
ReplyDeleteI'm seeing a lot of precipitation currently forecast for the Bellingham area during the first half of March (4-5"). I doubt this will verify but if it does we're looking at a very soggy early spring. Unfortunately, the forecast temperatures (highs mostly in the 50s and lows mostly in the 40s) are not supportive of building significant mountain snowpack except at alpine elevations - this will just be a lot of rain pretty much everywhere below ~5000'.
ReplyDeleteI first heard the term 50 years ago from Harry Wappler at KIRO-TV. There was a lot of dirty ridging in the winter of 1976.
ReplyDeleteI have a question about the term "ridge," used for a high pressure zone. Ridge implies height in some vertical dimension, over a relatively short distance in some horizontal dimension. In weather jargon, people talk about ridges all the time, but I've never heard anyone explain: what are those two dimensions? In other words, what are the two axes on which we would graph this "ridge?"
ReplyDeleteLike on a regular contour map, latitude and longitude, but instead of elevation it has pressure.
DeleteInteresting, and a lot of very cold air north of the BC border (-40F) being reported.
ReplyDeleteWon’t someone think of the children!?!1
ReplyDelete