New Years 2006 event

Picture of the Suisun Marsh Flood of Jan. 2006 (From Roos 2007). 

Environmental News Service reported that the flooding along the Russian River was the worst since 1997.  The crest associated with the event reach 10 feet above flood state at Guerneville and 5-feet above flood stage in Napa city sending water into the streets of the city.  1000 home were flooded along the Napa river.  There was also flooding of the Suisan Marsh area (see picture below).  The 3-day period ending at 1200 UTC 2 Jan was the fifth ranked event on our list.  The image below shows the areas that were hardest hit by the event were generally north of San Francisco Bay.  The California Department of Water Resources provided the following information on the flooding along the Napa and Russian Rivers. The return interval for the flooding on the Napa, Russian and Cosumnes Rivers from the rainfall on December 31 was 1 in 30, 1 in 15, and 1 in 50, respectively.  The return period for similar river stages along the upper Sacramento, Feather, American and Yuba rivers for a 3-day event was once every 5 years.  Widespread flooding was also reports in Nevada along the Carson River. 

Heaviest 3-day rainfall analysis using the CDC .25 deg by .25 deg unified data set ending 1200 UCT 02 Jan 2006. 

Higher resolution analyses of the 3 individual days that were included in the 3-day rainfall event (in mm).

Large area 4-panel chart,  200-hPa heights and isotachs (top left), 500-hPa heights and normalized height anomaly (top right), 850-hPa heights and normalized temperature anomaly (bottom left), and 1000-hPa height and normalized PW anomaly (bottom right) valid 0000 UTC 31 Dec. 2005.  The magnitude of the normalized anomalies are given by the color fill with the scale on the left had side of each panel.

Picture from California Department of Water Resources briefing slide

The atmospheric river associated with this event fit the definition of a strong one.  However,  the normalized anomalies associated with the event were not as high as during many of the extreme rainfall cases discussed within this training module.  The normalized PW maximum reached only 3.27 sigma which has only around a 1-yr return frequency where the anomaly was largest and less than that elsewhere.  The normalized MF anomaly was more impressive suggesting around a 3-year return period for the moisture flux in the vicinity of the Feather River.  Note the greater than 4 sigma normalized MF anomalies on the figures below.  

PW (mm) and normalized PW anomaly (magnitude of the anomaly scale is shown on the scale at the bottom of the figure)  valid 1800 UTC 30 Dec. 2005 (top panel), 1200 UTC 31 Dec. 2005 (bottom panel).

850-hPa winds (standard barbs and flags) and normalized anomaly of 850-hPa moisture flux (magnitude is given by the color fill from the bar at the bottom of the figure)  valid 1800 UTC 30 December 2005 (top panel), 1200 UTC 31 Dec. 2006(bottom panel).