These cP air masses form only in the Northern hemisphere and are most developed in the winter when they dominate cold weather conditions. An area covered by cP air experienced cold, stable air and clear skies. North America also has what is called Maritime Polar, or mP air masses. mP air masses are in the Northern hemisphere and exist Northwest and northeast of the North American continent over the Northern oceans. Within them, cool, moist, unstable conditions happen throughout the year.
Another difference between winter and summer is the Sub polar Low Pressure cells, or in other words, the North Pacific Aleutian Low, and the North Atlantic Icelandic Low. Both cells are dominant in winter and weaker or disappear in summer with the strengthening of high-pressure systems in the subtropics.
If you were to look at a global pressure map, you would find several high-pressure areas. The Pacific High, or Eastern Pacific High is one of these. The Eastern Pacific high is located East of Hawaii where the Pacific Ocean meets California. It dominates the Pacific in July, and retreats southward in January. The entire high-pressure system migrates with the summer high sun while fluctuating about 5*-10* in latitude. The Eastern sides of these anticyclonic systems are drier and more stable which means that there was less convective activity. There are cooler ocean currants than the Western sides.
Inductively thinking, we know that California is set up with Valleys, mountain ranges, and coastal regions, which means that we are prone to many weather effects. Deductively, I know that orographic lifting is very prominent on the coastal regions of California. The physical presence of a mountain acts as a barrier to migrating air masses. Orographic lifting occurs when the air is forcibly lifted upslope as it is pushed against a mountain. Stable air that has been forced upward by orographic lifting may produce stratiform clouds, whereas unstable air usually forms a line of cumulus and cumulonimbus clouds.
