It's because of the California current off the
west coast (which is cold) and the Gulf Stream off
of the east coast (which is warm). Hurricanes
lose strength over cold water, so they die before
they can make landfall in California
(although I have been in the eye of a remnant
hurricane that made it into central Nevada!). The
reason for these currents being where they are has
to do with the Earth's rotation.
Long answer (hint: you may want to ask your junior
high science teacher to explain parts of this with
The Earth spins from west to east. Because
the equator is farther away from the axis of the
Earth's rotation (which runs from pole to pole),
the surface of the Earth on the equator is
moving faster than the surface farther from the
equator, and isn't moving at all on the poles.
The ocean, being fluid, experiences drag due to
contact with other parts of the ocean. This
means that the ocean at the equator is slowed down
in its rotation and rotates slower than the rest
of the planet because it is experiencing drag from
the parts of the ocean farther north and south.
This has the consequence that, relative to the
continents, the ocean at the equator has a current
that is flowing from east to west, opposite the
direction of Earth's rotation.
When an equatorial ocean current hits (the east
coast of) a continent, it is deflected both to the
north and to the south. Being on the equator, this
current is warm, and so brings tropical warmth and
with it tropical weather (such as hurricanes)
along the eastern coast of the continent. As the
current it continues to flow toward the pole, it
eventually has to turn east as it gets to the
pole. Then, when this eastward-flowing polar
current hits (the west coast of) a continent, it
can only be deflected back toward the
equator, flowing along the continent's west coast.
Now, of course, it's been flowing near the pole,
and so is cold, and brings polar weather (such as
coastal fog) to the west coast of the continent.
The California current off of the California
coast is flowing south from the Gulf of Alaska,
and is therefore cold. The Gulf Stream along the
east coast comes out of the Gulf of Mexico, and is
therefore warm. Hurricanes over warm water gain
strength, so hurricanes can still be strong
when they hit the east coast. Hurricanes over
cold water lose strength, so by the time hits
California, it's just a rotating mass of
thunderstorms without a whole lot of powerful
winds. The former hurricane that I drove through
in Nevada was still recognizable as having once
been a hurricane because the thunderstorms were
arranged in curved arcs, and I knew when I was in
the eye because I could see the storms around me
in a circle, but there were gaps between the
storms that I could see between them.
disparity has to do with the typical
weather patterns in the Atlantic and Pacific
Oceans. Hurricanes form near the tropics.
prevailing winds (essentially the
direction that they blow most of the time) at
those latitudes in the northern hemisphere blow
from east to west. This means hurricanes are
blown toward the east coast of the US, but away
from the west coast.
Water temperatures also play a role.
The Gulf is typically quite warm, which helps to
maintain hurricanes. Water off the west coast
tends to be colder, and this reduces the strength
of any hurricanes which do come through.
Hurricanes form in warm, moist air over warm
water. Oceanic currents in the northern
hemisphere circulate clockwise, so warm water
from the equator flows to the Caribbean, Gulf of
Mexico, and the East Coast, while cold water
from the arctic flows to the west coast. The
warm water in the east provides lots of energy and
humidity for hurricanes to form, but in the west,
the water is too cold.