The question on Southern Californiansβ minds: So itβs humid here now?
Southern California summers arenβt exactly known for mugginess.
But uncharacteristic humidity has been clinging to the region for almost a month, and it looks like thereβs little relief coming our way.
Itβs not enough moisture to create much, if any, rain, but it is abnormal for this time of year
The dew point in Southern California is normally around 60 degrees at this time of year, forecasters say. But in downtown Los Angeles yesterday, the dew point hit almost 70 degrees.
Scientists say humidity generally becomes uncomfortable in the summer when the dew point is higher than 65.
βWe do get these prolonged periods of heat, but what is unusual is the humidity,β said National Weather Service meteorologist Bryan Lewis.
So, whatβs causing this mugginess?
A confluence of atmospheric forces, some hundreds or even thousands of miles away, is collecting and trapping moisture in Southern California.
βIt’s basically the combination of the warm ocean temperatures, as well as we’ve just been in the right pattern for some tropical moisture” to be sent our way, Lewis said.
Storms in the Pacific
Storms are to blame, at least in part, for the uncharacteristic humidity in the region this summer.
Two in particular have contributed to moisture levels in Southern California as they traveled across the Pacific Ocean in recent weeks.
Tropical Storm Fausto formed off of Central America earlier this month before moving off into the open ocean and moving toward Hawaii. It briefly was elevated to a Category 2 hurricane over the weekend before weakening again into a tropical storm.
Fausto is expected to continue weakening as it passes to the north of the Hawaiian Islands over the next few days.
The other, stronger storm, Hurricane Genevieve, also formed off the coast of Central America and has been moving relatively parallel to the Mexican coast, several hundred miles offshore.
Genevieve was elevated to a Category 5 hurricane on Monday.
The storms arenβt solely responsible for sending moisture hundreds of miles across the ocean.
Other weather patterns closer to home, including the system of high pressure air currently settled over the Western U.S. and the North American monsoon, siphon the tropical moisture from the storms into our region.
Thankfully, forecasters say, Hurricane Genevieve is not expected to create as much moisture as Fausto and other recent tropical storms.
Warming oceans
Forecasters also say warming ocean temperatures are adding to the humidity.
When the ocean is warmer than usual, the wind blowing inland off the water is also warmer. The warm seawater also evaporates faster, releasing more moisture into the air above it. That moisture is then carried inland by the wind.
Ocean warming is not new in Southern California, but itβs getting worse.
The region has been hit with a series of marine heatwaves over the last decade. They generally recede during the winter, but the current one has lasted for over a year. Scientists say these ocean heatwaves are likely being worsened by human-caused climate change.
But there is some short-term hope on the horizon for humidity-haters.
One, Hurricane Genevieve is not expected to pull as much moisture into our region as other recent weather patterns. And two, forecasters expect drier air to flow in from the northwest, cutting down the humidity a bit, especially inland.
That may not reach people who live along the coast, however, where the higher ocean temperatures will help keep the coastal humidity elevated, especially at night.