Tuesday, March 21, 2023 5:53 PM

Is there a hurricane off the California coast?


Californians this morning are waking up to rainfall and gusty winds, and if they pull out their phone to check the latest forecast and radar, they're seeing something that resembles a hurricane off the central California coast.

The radar shows a big, swirling area of low pressure that has developed a feature that looks like the eye of a hurricane with associated rain bands swirling around the eye-like feature on the radar. This, however, is not a hurricane, it's an extratropical cyclone, and there's a big difference in the way these two weather systems develop. Extratropical cyclones are cold core systems, that can exist over land or water, developing in the mid-latitudes whereas hurricanes are warm core systems that commonly originate more equatorially.

Radar Tuesday morning

Radar Tuesday morning

An extratropical cyclone develops and gathers strength as cold and warm air masses interact releasing potential energy to fuel the storm. Whereas a hurricane develops and gathers its strength from latent heat release as water vapor that has evaporated from the warm ocean waters condenses into liquid water fueling the hurricane. So essentially, extratropical cyclones obtain the fuel or energy needed to develop and strengthen from the temperature difference between cold and warm fronts and hurricanes get their fuel or energy from warm ocean waters.

It should be noted when extratropical cyclones are over waters warm enough to support hurricanes, typically around 70 degrees or warmer, if over the warmer waters long enough and if other atmospheric variables are favorable, extratropical cyclones can begin a transition into more of the warm core or hybrid system.

While extratropical cyclones and hurricanes are different in the way they develop and strengthen, they can bring some similar impacts at times with heavy rainfall, strong winds, and coastal flooding. In fact, extratropical cyclones can have impacts that extend farther away from the center of the low pressure. That is what is happening in California today as this extratropical cyclone is bringing strong winds to the state, pulling in copious amounts of subtropical moisture, and creating rough seas and increased tides along the coast.