Wetand News

There is a serious wildfire threat for western Oregon and southwest Washington on Friday and Saturday. Not the equal of September 2020, but serious enough that we need to be careful. This blog will describe the situation. Historically, major wildfires west of the Cascades crest occur in August and September for two reasons.   First, the surface "fuels" are dry after our typically arid summers.   Second, this is the season of strong easterly (from the east) winds as cool air --and associated high pressure--begin to move into the continental interior. Air accelerates from the interior high pressure towards lower pressure along the coast.  Strong easterly winds dry as they descend the western slopes of our regional mountains.  Strong winds can initiate fire and stoke it. The USDA Forest Service created the Hot-Dry-Windy (HDW) index, which correlates strongly with fire growth.   This index is essentially wind speed times a measure of dryness (called Vapor Pressure Deficit, VPD). 

 There is a lot of weather happening in the eastern Pacific. First, an unusually powerful low-pressure center, with intense rain and hurricane-force winds, is hitting northwestern Alaska (see surface pressure map at 11 AM Saturday).  A deep, 963 hPa low center.   This storm developed out of Typhoon Merbok, which underwent extratropical transition :  converting from a tropical storm to a midlatitude storm. https://oregonams.wordpress.com/2022/09/06/columbus-day-storm-60th-anniversary-meeting-with-professor-cliff-mass/ Reminder: I will be teaching ATMS Atmospheric Sciences 101 this fall. Like last year, I am teaching atmospheric sciences 101: a general introduction to weather and climate, this fall. You can learn more about the class on the style="color: #2288bb; text-decoration-line: none;"> class website . I talk about everything from the basics of the atmosphere to weather prediction, thunderstorms, hurricanes, and local weather to global warming and climate. I will be