Wetand News

 Yesterday (Friday, April 28) was the first moderately warm day of the Northwest "summer" season,  with temperatures ranging from near 90F along the western slopes of the Cascades to around 70F near the water (see a map of high temps below) Why were the warmest temperatures along the western slopes of the Cascades? It turns out that the Friday heat was very three-dimensional.   Water provided some cooling, but the situation was much, much more complex than that. We need to start with the sea-level pressure pattern, with the one at 11 AM Friday shown below.   High pressure over eastern Washington and low pressure over northwest Oregon and southwest Washington resulted in an easterly (from the east) wind moving over the Cascades.   But at low levels around Puget Sound winds were from the north, since pressures were higher over northwest WA and lower over western Oregon.  Near mountains, winds like to go from high to low pressure. A schematic of the situation around Puget Sound

A short Northwest heatwave is ahead and it will come on with a vengeance on Friday.    So get those tee shirts, shorts, sunglasses, and a cool drink ready.   It will be all the more jarring after an unusually cold spring. Many of you will experience temperatures in the 80s.... Let me start with temperatures predicted on Friday around 5 PM on Friday by the UW WRF model.  The white areas are places where temperatures are predicted to rise to 80F or more.  White hot. Temperatures will be cooler near Puget Sound and over Northwest Washington.  So if you like heat, move inland and south.  And cancel the trip to southern California--it will be warmer here!  Saturday will be a transitional day, with cooler air starting to move inland on the coast.  But still getting to the mid-70s in the western Washington and Oregon interior.  Expect further warming over the Columbia Basin, where mid-80s will be commonplace (see the forecast for 5 PM Saturday below). A state-of-the-science approach to foreca

Virtually every week someone asks me about a strange-looking weather radar feature that is often along the Washington coast. UFOs?  Chinese balloons?   A stationary flock of birds?   Or could it be the ocean?   The answer is revealed below. Below is an example on April 11th around 7 AM from the National Weather Service Langley Hill radar near Hoquiam Washington (the radar is shown above).   You see the bluish area west of Hoquiam, just offshore on the central Washington coast?  That is the feature.   The other features are areas of precipitation.  They move.  The area off of Hoquim stays put. The image above is for the lowest scanning angle that is typically used in U.S. weather radars, a half-degree (0.5 degree) above the horizontal.    However, the Langley Hill radar was giving permission to have a lower scan angle (roughly 0.2 degrees) due to the intercession of Senator Maria Cantwell.   The image from that angle at the same time is shown below. The feature has gotten stronger and l

 It is now certain that our region (and the entire western U.S.) will experience a welcome spring "heatwave", with substantial snowmelt causing a surge in river levels. The origin of the big change is the development of a major upper-level ridge along the West Coast later this week.  To illustrate, here are the forecast 500-hPa heights (think of it as pressure around 18,000 ft) for 5 AM Friday.  The red colors indicated heights/pressures well above normal).   This major ridge is associated with warmer-than-normal air that will rapidly sink, warming by compression. The latest National Weather Service predictions for Seattle indicate temperatures reaching the mid-70s on Friday and Saturday.  Add another ten degrees for the Columbia Basin. The recent UW WRF model forecast suggests that some places in the west will get into the 80s in western Washington, with Portland rising into the mid-80s. Folks are going to go wild after one of the coolest springs in Northwest history. And th

April 2023 has been starkly cool over the Pacific Northwest.  In fact, the second coolest on record in many locations.  The coolest in others. Just look at the April temperatures at Seattle and Pasco compared to normal highs (purple lines) and lows (cyan lines) is enough to put a literal chill down your spine. Most days have had lows well below normal and only ONE day during April reached the normal high in Seattle. A plot of the differences of temperature from normal for the past two weeks shows uber-cold maximum temperatures (blue color, 6-9F below typical) for much of Oregon and Washington.   This is historic cold.   For example, at Olympia, the average maximum this month so far was the COLDEST on a record going back over 80 years!   In Seattle, it was the second coldest (2011 was the chilly winner).   The bad news?  We will have to endure a few more days of these frigid conditions. The good news?   In roughly a week, a strong ridge of high pressure will build over the region bringi

There is an enhanced potential for wildfires over the western U.S. this coming summer and early fall, but it is not due to warming and drying. In fact, just the opposite.   A cool, wet winter has created an increased wildfire threat by producing a bountiful volume of flammable grasses.  A threat that extends from eastern Washington into southern California. Eastern Washington Near Thorp, WA, July 2022 When most people think of wildfires they usually refer to forest fires.  However, grass fires are just as important in the West, if not more so.  Furthermore, burning grass plays an important role in many forest fires.  Many of the most damaging fires in the western U.S. have had a large grass contribution.  For example, the eastern Washington town of Malden, which was destroyed in September 2020, and the 2018 Camp Fire around Paradise, CA. The distribution of seasonal grasses in the West is shown below (indicated by green colors).  There is a LOT of grasslands across eastern WA and OR, a

 One of the most frequent questions I am asked is where can one get the most skillful weather forecast. What are the best sources of weather information?   I answer the question in my new podcast. In the podcast I refer to a website, forecastadvisor.com, which provides updated comparisons of the forecast skill of various weather prediction websites (see sample below for Seattle's March forecasts). The WeatherUnderground and WeatherChannel are on top.  The National Weather Service is less skillful.    Do humans help produce better forecasts? What about TV weathercasters>  All will be revealed in the podcast. The Forecast Before I take on prediction skill, I talk about the cool forecast for the next week.  Seattle should be hitting around 60F every day.  As you can see below, Seattle will be much cooler than normal. To listen to my podcast, use the link below or access it through your favorite podcast service. Some major podcast servers:     Like the podcast? Support on Patreon 

  The Northwest Weather Workshop is the major local meeting for those interested in Northwest weather and is open to both professionals and interested amateurs.     It will take place on May 12-13, 2023 at the NOAA Sand Point facility in northwest Seattle, and is sponsored by the University of Washington, the National Weather Service, and Seattle/Portland chapters of the American Meteorological Society. The new agenda and sign-up information are all found on the meeting website: https://a.atmos.washington.edu/pnww/ .  As described below, this meeting will be in-person with a virtual option. The meeting is going to be a fascinating one (the current agenda is here ).   It starts on Friday afternoon (May 12) with a session on heavy precipitation and flooding, including a detailed look at atmospheric rivers and the historic 1962 "ARK" Storm.  Then we turn to a session on wildfire and smoke. Friday evening there will be a meeting banquet at Ivar's Salmon House, with a wonderfu

I have gotten a lot of questions and comments about the connection between a colder-than-normal spring and conditions during the summer. Several folks are convinced that a cold spring means a warm summer, mainly based on what happened last year.   So let's look at the data and find out! Let's start by plotting spring (March-May) temperatures over Washington State using the NOAA Climate Division dataset for the past century (through 2022).  Warmer earlier in the period, then cooling in the 1950s-1970s and then warming back to the earlier levels during the past decades.   I then identified the top ten coolest springs. Next, I determined the top ten coolest springs and plotted their anomaly (different) from normal (the averages for 1991-2020) temperature for the summer (July through September)-- below.    The result?  Summer surface air temperatures were substantially cooler than normal after cool springs. So based on climatology, there is no reason to expect a warmer than normal