Tuesday, July 23, 2019

Persistent Large-Scale Pattern with Critters in the Woods

I'm not sure how blogger will handle it, but the loop below has been purposefully designed to run at high speed and to repeat to illustrate three key points about the GFS forecast for the next ten days. 

First, the large-scale pattern changes little with persistent upper-level ridging over the southwest U.S. and the westerly mid-latitude jet to our north.  There are variations in the strength of the ridge and the center of its circulation, but these are relatively modest.

Second, one can see precipitation "pulsing" in the lower right-hand panel, which depicts the surface forecast and includes the 3-hour accumulated precipitation.  This pulsing reflects the influence of the sun, with precipitation increasing and becoming most common later in the day and in the early evening and becoming less common over night. 

Third, as can be seen in the top two images which depict the upper-level pattern, there are some "critters in the woods" in terms of upper-level waves that are in the westerly jet to our north or moving in clockwise fashion around the upper-level ridge.  These smaller-scale features modulate the coverage, location, and intensity of the precipitation. 

Put it all together, and this is a very typical July pattern, as illustrated by the weather.com 10-day forecast. 

Source: weather.com
Personally, I'm already dreaming of September....

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