The main difference between east coast and west coast storms is that often during the winter, in the eastern U.S., a second low presure center (storm) forms to the southeast of the primary storm. Once the secondary storm develops the primary storm then dissipates. The new storm may intensify rapidly and
become much more powerful than the original storm. West coast storms moving in from the Pacific Ocean may deepen or intensify as they approach the coast, but new storms rarely form. This makes predicting the track the storm will take, and as a result the amount of precipitation likely to fall, somewhat easier. The Appalachian Mountains seem to be a transition area between
where primary storms weaken and secondary storms develop. Many of these secondary storms develop in the northeastern Gulf of Mexico and off the coast of Georgia and the Carolinas. Knowing just where these new storms will suddenly appear makes forecasting the track they are likely to take a
challenge. Numerical models which simulate atmospheric conditions have become more accurate in forecasting these storms over the last decade. However, they are not always reliable. The Gulf and Atlantic coasts seem to favor
secondary storm development probably because cold air trapped to the east of the Appalachian's is in close contact to warm, moist air over the Gulf and the Atlantic. The shape of the coastline also plays a role in where storms redevelop. Concave coasts (coasts that buldge outward into the ocean, such as the North Carolina coast and the New England coast) tend to promote the development of the secondary storms.
Why is it that even though the ocean water off the west coast is cool and the water off the east coast is relatively warm, big snows often fall on cities near the Atlantic coast, but the west coast storms bring usually only rain to cities on the Pacific coast? The reason for this is that in the Northern Hemisphere srorms spin in a counterclockwise direction. This means that air from the north is pulled into northern and western sectors of the storm as it moves from west to east. For storms off the Atlantic coast, this is cold continental air form Canada, however, for the Pacific storms, the air to the north is marine rather than continental, and is only slightly cooler.
Where else might you expect east coast type secondary storms to form? The answer to this question is the east coast of Asia (China, Korea, Russia, and Japan).
How are wintertime east coast storms different from west coast storms in the U.S., and where else in the world is likely to experience storms similar to those that effect the Atlantic coastal states?