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Why the weather flip-flopped out West
Northwest dried out as the Southwest drowned
 Jed Conklin / The Spokesman-Review Above-average temperatures in January and February, coupled with record low levels of precipitation, have kept these fields north of Spokane, Wash., bone dry. Washington State is currently under a drought emergency. |
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A desert blooms Record rain has transformed the normally desolate Death Valley into a wildflower paradise. |
It's been a crazy winter out West. A flip-flop in storm patterns has caused the typically moist Pacific Northwest to go dry while making "flood watch" a common phrase in the Southwest.
Scientists aren't surprised it happened, but the severity of the shift caught them off guard.
Winter storms pick up moisture as they travel across the Pacific Ocean, and they typically dump much of that moisture on places like Portland and Seattle, making Southern California and Arizona good places to putter around golf courses and lounge by pools.
This season, however, many storms have been deflected south by climate variations in the Eastern Pacific, including warmer water and persistent areas of high atmospheric pressure.
By the numbers
The February numbers mimic a pattern that goes back to December and has continued into March:
- Seattle received 1.2 inches of precipitation in February — 29 percent of the average for the month.
- Los Angeles endured more than 11 inches of February rain, three times normal.
- Phoenix got 3 inches of precipitation last month — nearly 400 percent of normal.
In Phoenix, a river that's been dry since 1999 has run bank-to-bank on several occasions this winter as officials released water from lakes swollen from the second wettest winter in the city since the 1940’s.
Rain-induced mudslides have become common this winter in Southern California.
What's up?
"The Eastern Tropical Pacific warmed and gave us El Nino-like conditions," explained Greg McCabe, a scientist with the U.S. Geological Survey (USGS). "When we have warm Eastern Tropical Pacific temperatures, the Northwest is dry."
In El Nino years, easterly tropical trade winds in the Pacific Ocean weaken and the waters along the Eastern Pacific Ocean become warmer. This warmer ocean water supplies both moisture and energy for huge thunderstorms, which feed moisture and wind energy into the upper atmosphere. Some of this moisture eventually dumps on the West Coast, creating severe winter storms.
Similar correlations between flood and drought have been observed on a global scale, between the Amazon and Congo rain forests.
Meteorologists had been predicting dry conditions in the Pacific Northwest and wet weather for the Southwest since early in the year. What surprised them was just how dry, and how wet, it got.
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