Unique and descriptive
terminology has a tendency to be linked with weather and many of its processes.
How many times have you heard phrases like "howling winds" or "raining
cats and dogs"? These terms give action qualities to some of the wild aspects
Pineapple Express is another
descriptive term that is used frequently in the media and is linked with heavy
rain and flooding. Actually, it develops during a relatively common weather
pattern with a ridge over the West Coast and a low pressure in the Eastern Pacific.
Southwest winds ahead of the low pressure drive warm, moist air over the ridge
into the Pacific Northwest and California. This leads to widespread cloud cover,
persistEnt rain and unseasonably warm temperatures. The flow of warm air can
melt the snow pack in the mountains, while periods of heavy rain occur when
the warm moist air is forced over the mountainous terrain. Rapid snow melt paired
with heavy rain leads to extensive flooding.
Forecasters often refer
to this warm, moist air flow as the Pineapple Express because it originates
from the subtropical waters around Hawaii where pineapples are typically grown.