A slow-moving storm system tapped into tropical moisture to bring record rainfall to parts of the Northwest over the past week. Stampede Pass in western Washington received 8.22 inches of rain on Monday the 5th of November 2006 to set a new all-time one-day total. Six rivers reached record crests in the region. So far, one person has died, and two are missing as a result of the flooding. The weather pattern responsible for all of the rain is known as the "Pineapple Express". The Pineapple Express is really just the subtropical jet steam. Moisture originating around the Hawaiian Islands is carried northeast by the subtropical jet steam towards the West Coast. This moisture can then be drawn into storm systems as they approach the West Coast. The coastal topography also aids in squeezing out the moisture as air is lifted over the mountain ranges.

The TRMM-based, near-real time Multi-satellite Precipitation Analysis (MPA) at the NASA Goddard Space Flight Center monitors rainfall over the global Tropics. MPA rainfall totals are shown here for the period 31 October to 8 November 2006. The highest rainfall totals for the period are on the order of 250 mm (~10 inches, shown in darker red) and occur over Mount Olympus west of Seattle, Washington. The orographic enhancement of rainfall is evident as most of the heavier rain (8 inches or more, shown in red) is located over the coastal range or along the windward slopes of the Cascades. Some areas of heavy rain, however, do extend out over the Pacific off of the Washington coast.

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TRMM is a joint mission between NASA and the Japanese space agency JAXA.

Images produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC).