This week’s dire weather forecasts, and public safety warnings, are filled with some unfamiliar terms and abbreviations. Here are a few and what they mean, per the National Weather Service, UCLA and the Sierra Club.
Santa Ana winds: Dry, downslope winds from the north, northeast or east that blow from the desert toward the sea in Southern California, usually from October to March.
The winds are often warm up and sometimes turn hot — but not always. The current Santa Ana event is cold, because it drew lots of cold air from Canada. Southern California ski resorts may easily be able to make snow over the next few days.
The Santa Anas range from weak to extreme in power. In the past, the winds have gusted more than 90 mph in San Diego County’s Cuyamaca Mountains.
Mountain waves: The current wind event originated in the Nevada and Utah regions of the Great Basin, where high pressure produced winds that are flowing into Southern California.
That’s leading to the creation of mountain waves, which arise when strong winds blow perpendicular to a mountain range. The waves shoot down the coastal side of the mountains, gaining speed along the way, and are more casually referred to as simple Santa Ana winds.
High wind warning: Such a warning is issued when forecasters expect either sustained winds of 40 mph for at least an hour, or gusts of 58 mph or more.
A high wind watch, on the other hand, is issued when winds are expected to be weaker but gusty.
Red flag weather warning: A National Weather Service alert that warns the public — especially fire officials and firefighters — that strong winds are expected in specific areas of Southern California, and that there will be potentially dangerous fire weather conditions within the next 12 to 24 hours.
Such an alert is usually issued when a combination of high winds, low humidity and high temperatures is expected — but that’s not always the case. The current warning was issued because forecasters expect strong winds and low humidity to hit terrain that’s unusually dry due to a lack of rain.
Much of San Diego County is covered by chaparral, the most flammable form of vegetation in the U.S.
“Particularly dangerous situation” (PDS): A rarely-used term that means specific areas could be struck by extreme, damaging weather — in this case, the Santa Ana winds.
On Monday, National Weather Service in Los Angeles issued a PDS for areas in and near Los Angeles County. That alert was followed on Tuesday by a huge wildfire in Pacific Palisades in Los Angeles, south of Malibu.
Public safety power shutoffs (PSPS): You may be more familiar with this similar abbreviation for a different term.
Public safety power shutoffs refer to planned outages that take place when utilities such as San Diego Gas & Electric preemptively shut off power supply to some lines to prevent wildfires from sparking.
Spotting: This refers to how fires can throw off sparks that drift in the air, then settle, igniting additional fires — known as spot fires.
Firenado: Forecasters define this as a short-lived, spinning column of fire, ash and smoke that can resemble a tornado. This weather phenomenon occurs when a wildfire or other source of intense heat causes hot air to spin and create a column of fire.
