Near Historical dry February hits California (Photo Credit: University of Nebraska-Lincoln Drought Monitor)
DISCUSSION: February is normally one of the wettest months for much of California. However, this February has been one of the driest in recent history for many regions of the state especially the San Francisco Bay Area. In most locations of the Bay Area, there has been no rain recorded including in San Jose, San Francisco, and the commonly wet locations of Napa and Sonoma. In addition, to the unusually dry conditions for much of the state, the Sierra Nevada range has received minimal new snow and is below normal of total snowfall for the rain year as the Sierra Nevada has reservoirs such as Hetch Hetchy which provides drinking water to areas including San Francisco.
One of the biggest reasons for the lack of rain has been due to many ridges over California. A ridge is an area of high pressure where there is a maximum in the curvature of the winds in an anticyclonic (clockwise) motion. In addition to the consistent ridges, the low pressure systems that tried to move through were either dry or most of the moisture went east towards the Great Basin and the Sierra Nevada mountain range while missing most of California. The moisture was driving to the east in the upper atmosphere due to the flow of the wind due to the pressure differences and the curvature of the Earth. However, on February 22, a small low pressure system brought some sprinkles to parts of California including the Central Coast and the Central Valley, however, it was not enough to relieve the dryness or even make a big impact. In addition, parts of Southern California and Arizona received moisture in this time period due to moisture being drawn from the warmer portion of the Pacific Ocean near Baja California.
However, there is not all bad news due to the dry February. Many of the reservoirs especially closer to the Sierra Nevada such as Don Pedro and Lake Oroville are near or above average in how much is being stored at the moment compared to historical. In addition, a few locations such as San Diego and the northern coast cities such as Eureka and Crescent City have received above average monthly rains. Due to the dryness of January and February, much of the state has been placed in the abnormally dry category of the drought monitor with moderate drought levels for the Central Valley. A drought monitor is a way to show the cumulative lack of moisture in certain areas. However, counties such as San Bernardino, Riverside, San Diego, and Orange in Southern California are not in drought or dry conditions due to the amount of rain they received overall in the year.
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©2020 Meteorologist JP Kalb