San Francisco resides on the northern California peninsula, surrounded on three sides by oceanic water such as the Pacific Ocean, the Golden Gate strait, and the San Francisco Bay. San Francisco is generally affected by continental tropical and maritime air masses which usually include maritime polar and very rarely maritime tropical. The Pacific air keeps the temperatures in this region generally moist and mild. Due to the region's diversified and steep topography, micro-climates result within the region. Winds flowing over the mountainous terrain and high hills result in diversified temperatures across short distances. The most distinctive feature of the local climate is the banks of fog that can roll in off the ocean, quickly covering various areas of the city, and then disappear just as quickly. The infamous San Francisco fog is usually seen on summer mornings, coming off the cooler ocean and backing up against the hills, but it also comes from the colder inland areas during the winter. The fog affects different elevations in varying amounts, covering the city in complex.
**Figure 1 and 2 depict the monthly average for rainfall and temperature for San Francisco**
Figure1.
Figure 2.
Storms..
Even though the cool oceanic waters of the Eastern Pacific prevent tropical storms from reaching San Francisco, the region still experiences its share of mid-latitude cyclones. Additionally, most of the precipitation in San Francisco falls between November and March, averaging about 10 days per month. Precipitation in the winter season of the California coast are mainly due to occluded fronts on a trajectory from the west-northwest, and an occasional cold front from the Gulf of Alaska. These high pressure systems are driven south in the winter as the Pacific High drifts south and westerlies and Polar jet stream dip south of 40 degrees N. Winter thunderstorms occur on the average only twice per season in higher elevation due to cold unstable post-frontal air masses.
Spring and fall often produce quiet and calm weather for San Francisco. These seasons usually produce the most cloud-free days between the overcast days of summertime stratus and the rain laden clouds of winter. San Francisco's hottest days are typically during the spring and fall when high pressure builds into the Pacific Northwest and Great Basin, and dry offshore winds replace the Pacific sea breeze. The three hottest days in San Francisco occurred in September and October (ggweather, 2014.)
Figure 3.
A mid-latitude storm brewing over Bay Area
Spring and fall often produce quiet and calm weather for San Francisco. These seasons usually produce the most cloud-free days between the overcast days of summertime stratus and the rain laden clouds of winter. San Francisco's hottest days are typically during the spring and fall when high pressure builds into the Pacific Northwest and Great Basin, and dry offshore winds replace the Pacific sea breeze. The three hottest days in San Francisco occurred in September and October (ggweather, 2014.)
Figure 3.
A mid-latitude storm brewing over Bay Area
San Francisco Weather Forecast
As seen in figure 4. a strengthening in the upper level ridge near the West coast will result in warmer temperatures and less clouds for Sunday April13th. The ridge will eventually weaken in a day or so thus bringing cooler temperatures.The storm will remain North of San Francisco resulting in dry conditions.
Figure 4.
Figure 4.
Sources Cited:
na. Climate of San Francisco. Golden Gate Weather. ggweather. 2014. web. 12 April 2014.
na. San Francisco. United States Dept. of Commerce. Noaa. 2014. web. 11 April 2014.
na. San Francisco climate. Accuweather. Image. 2014. Web. 12 April 2014.
na. San Francisco. Image. City-data. 2014. Web. 12 April 2014.
Eardman, Jonathan. San Francisco, California. Image. Weather. 2014. Web. 12 April 2014.
Read, Wolf. The Storm King. ImageWashington. 2014. web. 12 April 2014.
