Weather 101 is a series of articles where News10’s meteorologists answer your weather questions.
Brian Hassett from Cobleskill asks, “I am always curious about storms in the Pacific and how you guys know pretty much how they will track to us.”
We are in a part of the world called the “Mid-Latitudes,” between the North Pole and the tropics. Here, the large-scale weather patterns generally move from west to east. For that reason, systems that impact the West Coast move across the country and often impact our weather.
But what leads to those west-to-east patterns? Buckle up, this is where we go in depth…
The sun’s rays hit the tropics at a more direct angle, creating warmer air that has a tendency to rise – think of using a wood stove to heat your home.
Warm air rises and the second floor gets very toasty very quickly – In the same way, the air over the tropics rises until a certain point, at which point it starts to spread away from the equator, both to the north and to the south.
That warm, tropical air headed north doesn’t make it all the way to the North Pole uninterrupted. Because of the earth’s rotation, much of it builds up over 30° North latitude (around Florida, Texas, Baja California, etc).
That buildup leads to high pressure, causing the air to sink.
As the air approaches the earth’s surface, it flows outwards from that area of high pressure. Because of something called the Coriolis Force, air tends to turn to the right in the Northern Hemisphere.
That means that the air flowing north from the high pressure turns to the right, and ends up flowing from west to east. These are what we call the “Prevailing Westerlies,” and they’re the reason we track storms all the way from the West Coast to the Capital District.
On the flip side, the air flowing south from that high pressure also turns right, and ends up heading from east to west. This creates what we call the “Trade Winds,” and they’re the reason we track hurricanes from the coast of Africa all the way to the Caribbean.
Of course, these storms always change and evolve as they travel these hundreds or thousands of miles. Traveling over the Rocky Mountains, in particular, can radically change any system. We will never see the exact same storm as California or Washington state… But to be able to have an idea of what’s coming our way, it’s necessary to keep an eye on what’s happening out west.
Do you have a weather question you’ve been dying to ask? Send an email to Matt Mackie (firstname.lastname@example.org) or Rob Lindenmuth (email@example.com) to get it answered in Weather 101!