Wednesday, August 17, 2011

Smoke & East Pac Tropical Depression

Much of the smoke that filled the Salt Lake Valley has dissipated.  PM levels have dropped from yesterdays maximum, although they remain somewhat elevated over background values from the past several days, suggesting we still have a bit to go until we're "free and clear."

Source: Utah Division of Air Quality
The Madweather Blog noted this morning that tropical depression Seven E formed off the southern coast of Mexico yesterday.  The two day loop below shows the development nicely, including the slug of high precipitable water air accompanying the depression.

Infrared satellite, 925-mb wind, and precipitable water loop
valid 1600 UTC 15 – 1300 UTC 17 Aug 2011.
We're creeping into the time of year when remnants of eastern North Pacific tropical cyclones have a habit of rumbling through the southwest.  As shown by Ritchie et al. (2011), the frequency of eastern North Pacific cyclones peaks in August, with the frequency of events with remnants that impact the southwest United States peaking in September.

Source: Ritchie et al. (2011)
However, the 0600 UTC GFS calls for the slug of precipitable water presently accompanying Seven E to move off to the west-northwest, avoiding the southwest during the next week.

0600 UTC 17 Aug 2011 initialized GFS 925-mb wind and
precipitable water forecast valid 0600 UTC 17 Aug –
0600 25 Aug 2011.
I haven't had a chance to check out the GFS ensembles to see if some of the members bring in the remnants of Seven E, but will be keeping an eye on it over the next few days and an eye on future tropical cyclones that develop in the east North Pacific.

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