The Pineapple Express

A jet stream coupling which occurs such that the subtropical jet out of Hawaii reaches Oregon is called the Pineapple Express. While this is rare occurrence, in recent years the frequency has increased (Greenhouse effect?) and this jet stream pattern was the cause of the 3 floods in the Willamette Valley in 1996.

In mid-to-late May, there is often an occurrence of this phenomenon which brings unusually humid air to the valley and occasional strong showers and thunderstorms. This most recent occurrence (1997) was mild compared to the one in late May 1993 which produced impressive thunderstorms and established the May precipitation record.

Now you know.