Today is February 29, Leap Day.  It’s also the last day of meteorological winter, which is defined as December 1 – February 28/29 in the Northern Hemisphere.  Of course, you don’t need me to tell you that winter is over in the Pacific Northwest – the weather these past 2 weeks has spoken for itself.  It’s perfectly normal for our climate, by the way:  Late February is, on average, warmer than late November, which is still considered part of “autumn.”

We had two stretches of ‘false spring’ this month.  The second stretch ran from Wednesday through yesterday Friday, with high temps at PDX reaching 57-62-59 under mostly sunny skies.  That’s not nearly as warm as it CAN get at this time of year; with a sufficiently warm airmass and the same sun angle as mid-October, it can hit upper 60s or even 70 under a perfect setup.  Still, 60-degree sunshine in February always feels especially magical, kind of like how it does in late autumn.

Yesterday afternoon I went first on a short stroll in downtown Portland, then got together with fellow WeatherTogether blogger Charlie Phillips for a hike in Forest Park.  It’s interesting to note just how much the early flowers and buds have progressed this year; we’re well ahead of “normal” late February phenology.  This is almost entirely due to the unusually warm January; temps in February have been remarkably close to normal despite all the sunshine.

Clouds started to roll into the city around 3pm, just at the time that Charlie and I were heading up to Forest Park for the hike.  I’m actually glad it wasn’t TOO warm during the hike; I’m a bit out of shape and broke quite a sweat trudging up those hills.  There are over 80 miles of trails in the urban forest out there; it’s always a wonderful getaway no matter the season.  As part of my tradition of tracking early spring phenology, here are some of the photos along the Wild Cherry Trail:

In poetically perfect timing, the rain arrived right around 5pm yesterday, just as the hike was finishing.  Today Saturday is the first of a series of cooler and more active weather days.  We had showers and a few hail storms across the region today, with snow levels in the mountains as low as 1,500 feet.  The next chance for rain is Monday-Tuesday, then a stronger and colder storm system moves in Thursday evening.  The 12z GFS shows very low snow levels Friday into Saturday morning.  The 1000-500mb “thickness” drops to under 5,220 meters during this trough, which is indicative of a very cold March airmass overhead.  As of right now it doesn’t look quite cold enough to bring a dusting of wet snow to Portland and the Willamette Valley floor, though.  It’s always annoying when we put a fork in Winter, only to have something like that pop up in early March.

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On the topic of Leap Day.  The reason why we have it, of course, is that the Earth’s orbital year doesn’t not divide into a whole number of days.  There are approximately 366.239 rotations of the Earth’s axis per revolution around the sun, or 365.239 “synodic” days.  The way our Gregorian calendar system deals with this ugly fraction, is to have 97 out of every 400 years with a leap day.  Most years that are multiples of 4 are leap years, as well as all years with a multiple of 400.  The exception are years that are a multiple of 100 but not 400; century years like 1800, 1900, 2100, etc.

If we didn’t have any leap years at all, the timing of solstices and equinoxes would become about 5 hours and 49 minutes later each year.  If we had leap days every single fourth year with no exceptions, the timing would become about 45 minutes earlier each 4-year cycle.  Skipping leap years in three out of four century years has the effect of keeping the dates steadier over the long-term.  Even this system isn’t perfect; at some point under the Gregorian calendar, extra leap days would need to be added in order to keep everything well-synchronized.

Well that’s about it for now.  March is going to start cool and unsettled, with a slight chance of  a late winter ‘tease’ on Friday.  But for the most part, Spring 2020 is here already!  -Karl