Key Takeaways
- Central California is experiencing a prolonged period of tule fog, which has been present in the region since November.
- The fog is caused by a combination of cold air, moisture, and calm winds, and is trapped in the Central Valley by a temperature inversion.
- The fog has led to colder-than-usual temperatures in the region, with average lows of 37F and average highs of 63F in the Central Valley.
- The fog is also affecting the Bay Area, with temperatures lowered by the fog moving out of the Central Valley and into the region.
- Climate scientists believe that warmer overall conditions, including warm ocean water and lack of snowpack, are contributing to the persistence of the fog.
Introduction to Tule Fog
The Central Valley in California is currently experiencing a prolonged period of tule fog, which has been present in the region since November. This type of fog is not uncommon in the area during the colder months of the year, but the current episode is notable for its duration and extent. The fog is caused by a combination of cold air, moisture, and calm winds, which allow the moisture in the air to condense into a thick layer of fog. The fog becomes trapped in the bowl-like shape of the Central Valley, where it is prevented from rising by a layer of warm air above, known as a temperature inversion.
Formation and Movement of Tule Fog
The tule fog first formed over central California in November, following a major storm that hit the region in late October. The storm caused significant damage and disruption, and was described by the National Oceanic and Atmospheric Administration as the "worst severe thunderstorm outbreak over the central California interior in recent memory". The fog has since persisted, moving slowly through the Carquinez Strait and into the San Francisco Bay. The National Weather Service has issued several dense fog advisories in the region, warning of reduced visibility on mountain roads and potential hazards for travelers.
Impact on Temperatures and Visibility
The lingering tule fog has contributed to the chillier conditions being experienced by locals in central California and the Bay Area. The Central Valley has seen average low temperatures of 37F and average high temperatures of 63F so far this month, while the Bay Area has experienced average lows of 43F and average highs of 65F. The fog has also reduced visibility in the region, with the National Weather Service warning of "sudden drops in visibility to less than 1/4 mile" in some areas. This has made travel conditions hazardous, particularly on mountain roads where the fog can be especially dense.
Climate Factors Contributing to the Fog
Climate scientists believe that warmer overall conditions are contributing to the persistence of the fog. Daniel Swain, a climate scientist at the California Institute for Water Resources, notes that the warm ocean water offshore and the lack of snowpack in the Sierra Nevadas have led to "relatively warmer surface temperatures", which is causing the temperature inversion and preventing the fog from lifting. This is consistent with the views of Carlos Molina, a National Weather Service meteorologist, who told the Los Angeles Times that tule fog typically lasts about a week, making the current episode "on the extreme side".
Conclusion and Outlook
In conclusion, the tule fog currently affecting central California is a significant weather event that is having a major impact on the region. The fog is caused by a combination of cold air, moisture, and calm winds, and is trapped in the Central Valley by a temperature inversion. Climate scientists believe that warmer overall conditions are contributing to the persistence of the fog, and it is likely to continue to affect the region for some time to come. Residents and travelers are advised to exercise caution when traveling in the area, and to stay up to date with the latest weather forecasts and advisories.
