As the California Wildfires continue to spread around Los Angeles the humidity continues to plummet which creates a very dry climate to propel these fires.
In nearby Burbank this week on Mid Day Friday temperatures were in the upper 60’s with a comfortable relative humidity of 50-60%. But then later in the day the Northeast Santa Anna Winds arrived from higher pressure over the inland deserts and lower pressure on the coast. Those winds coming from the very arid deserts are already hot and dry to begin with but as they climb over the Sierra Nevada Mountains and closer to LA the air sinks and undergoes additional warming and drying process from compressional heating. These winds have a downward spiral from the upper atmosphere compressed by the warm, dry ground temperature.
By later afternoon the temperatures zoomed into the upper 70”s and low 80’s and more importantly the dew point and relative humidity plummeted. By 6;00 PM the dew point had dropped to a SUPER Arid -7 Degrees (yes that is correct) meaning the air would have to cool to 7 below zero for fog to form. That made the relative humidity at 4%. These conditions create critical fire conditions where the wildfires can spread.
With humidity at unprecedented lows of 3-4% the average homeowner can understand how dry this is. During the winter with outside temperatures in Cincinnati at 25-30 degrees with indoor humidity at 30% the homeowner would feel very dry. So to have 3-4% Humidity outside would fee unbelievably dry perfect for fire conditions.
Hopefully during the next few days the winds will calm down in California and they will see some rain for the fires to quit burning.