Real-time Insights on the February 1-4 Precipitation Event

The sixth significant weather event of the water year brought impactful rain, snow, and strong winds to California.  The majority of precipitation accumulation was concentrated in Northern California, with less substantial totals down into the San Joaquin Valley.

Event Analysis

We can assess the February 1-4 storm's impact using near real-time National Weather Service data. Be reminded, this data set is not fully representative and provides only an estimate of WY precipitation totals. ‍

Regional Highlights:

• ‍Region 1 (LKLA): No station data was reported for the Lower Klamath region during this event.‍
• Region 2 (SYFA): The Sacramento, Yuba, Feather and American region saw a big impact, with a 12.39% increase in WY precipitation from February 1-4. Both Redding and Blue Canyon Airport had similar storm totals of 7.32” and 7.36”, respectively—the highest in that region. For Redding, that marked a nearly 22% increase in WY percentage and brings that station to 84.82% of WY normal.‍
• Region 3 (RNSF): The San Francisco Bay area also saw a significant increase of 9.31%.  Santa Rosa added another 4.9 inches, resulting in a 14.51% gain and reaching an impressive 97.81% of WY normal—the highest total WY percentage across all reporting stations.‍
• Region 4 (SNJQ, TBVL):  Precipitation totals in the San Joaquin and Tulare region rose by a mere 1.69%.  Stockton received 0.67”, the most significant accumulation in the region.  ‍
• Regions 5-7: In these regions, only trace amounts of precipitation were recorded.‍

‍Northern Sierra, San Joaquin, and Tulare Basin

The 8-station, 5-station, and 6-station indices shown below provide insight into how the Feb 1-4 storm event impacted these regions. This year’s analogs (2017-18 and 2018-19) are shown alongside the current water year in each plot, with the timing of the Feb 1-4 event marked by a vertical red bar. 
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All three regions experienced a boost in precipitation during this period:  The Northern Sierra gained close to 11 inches, the San Joaquin 2.4 inches, and the Tulare around 1 inch.  WY totals give perspective to these numbers: 

• The 8-station WY average is 53.20 inches; a gain of 11 inches represents ~20%.
• The 5-station WY average is 40 inches; a gain of 2.4 inches is ~6%.  
• The 6-station WY average is 28.3 inches; a gain of 0.9 inches is ~3.2%.
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Putting It All in Perspective

The graph below highlights the impact of each significant precipitation event this water year, helping to visualize each storm’s magnitude and reach within the broader context.  
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‍A Word About Southern California

Unfortunately, the February 1-4 storm failed to improve conditions in Southern California; it remained dry (right) and wildfire threats are still critical. However, a second storm is currently impacting the state and is expected to bring much-needed precipitation to the region, including Los Angeles County. The Los Angeles forecast office anticipates "generally beneficial rainfall," with 0.5-1.0 inches across most areas and up to 3 inches in the coastal mountain ranges (Los Angeles, CA). We will continue closely monitoring this system.

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