The West Coast Thermal Trough

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Presentation transcript:

The West Coast Thermal Trough

The Most Important Summer Mesoscale Feature of the West Coast of North America An inverted pressure trough based out of the Central Valley of CA that can extend into the Pacific Northwest 925 hPa heights and temperature

JJA -36h 925mb 925mb 500mb 500mb

JJA -12h 925mb 925mb 500mb 500mb

JJA Start 925mb 925mb 500mb 500mb

JJA End 925mb 925mb 500mb 500mb

JJA +12h 925mb 925mb 500mb 500mb

A Case Study The WRF model was initialized at 0000 UTC 13 May 2007 using NCEP’s GFS model and the model ran for 72 hours. Nudging toward the GFS was turned off so this run (Control) may be compared to runs with terrain modifications and without surface heat and moisture fluxes.

WRF 36-km terrain

WRF 36-km heights and wind at 500 hPa

Some interesting details Warmest weather is the last warm day, when trough is overhead and about to move east of the Cascades When trough is to the south, northerly flow pulls cool air in form the north. Strong easterly flow can cool Seattle because of troughing on western slopes of Cascades.