A bit about the Vernal equinox

Friday (March 20) at 5:44 AM (mountain time), Spring officially begins in the northern hemisphere (and the weather will definitely feel the way you expect it to for the season).

The astronomical event is the Vernal equinox, when the sun crosses the celestial equator (the projection of earth's equator onto the sky), heading northward. The sun will be directly overhead at the equator, and will rise directly east and set directly west for one of only 2 days during the year. (the other 363 days, it rises and sets either north or south of east and west. Take a look and see for yourself).

The word "equinox" comes from the latin words meaning "equal night", as the general belief is that on the equinox, you experience 12 hours of daylight and 12 hours of darkness...but that's only true close to the equator.

The further from the equator you are, the further from a 12-hour day you'll find yourself. For example...in Colorado Springs, (approximately 39 degrees north latitude), the sun will rise at 7:02 and set at 7:11. That's 12 hours and 9 minutes. Pueblo will see (official) sunrise at 7:01 and sunset at 7:10, again a 12 hour and 9 minute day...so it's close, but not on the 12 hour mark.

In more general terms, this is the "March Equinox", which takes into account that it's the beginning of FALL for many cities in the southern hemisphere.

By the way, thunderstorm season follows the sun, so the higher in the sky the sun climbs (and the warmer it becomes), the more likely we are to hear the rumble of thunder.

This March could be one for the record books

So far, March in southern Colorado has featured record highs, gusty winds and little, if any precipitation. Between Colorado Springs and Pueblo, Colorado Springs is the champ, with .07" through Friday the 13th. Pueblo has had a couple of days with a trace of moisture, but that doesn't count as "measurable" precipitation (in order to be measurable, it must be at least .01").

If this trend continues, that would make it the first March since records have been kept (since 1888) that Pueblo hasn't received "measurable" rain or snow.

The month is only half gone, but the chances for rain/snow over the next 10 days or so doesn't look terribly likely.

I'll keep you posted.

Atmospheric Visibility, or "Where did the mountains go?"

A good question from Carrie,
"I'd like to know why you can see the mountains to the south (like the Spanish Peaks) only on certain days. It seems like the best times to see them are on cold, partly cloudy days in winter. I'm really curious as to the science pertaining to this!"
And the answer is...
How well you can see the mountains depends on a number of factors that affect the visibility, such as dust and haze…but the situation you describe, “partly cloudy [or clear] winter days” is all about the amount of water in the air. When it’s colder, there’s usually less moisture = better visibility. Good job on spotting the key!

Colorado's warm, dry spell

At least 2 record highs today in Colorado. Colorado Springs tied it's 1901 record of 72, and Pueblo put a new page in the record books with an 80 degree reading (78 was the old record, set in 1904).

When I'm out and about, I've been getting the question "is this REALLY unusual?", and "is this proof of global warming?"

Let's deal with those one at a time...The answer to the second one is NOOOOOOOOOOOO!!!!!!!!

Now then, back to the first one. We can go through wide swings of weather this time of the year, as we begin to transition from cold, wintry weather from the north and more springlike conditions, usually caused by high pressure to our southwest driving warm, dry winds down the eastern slopes of the Rockies...and that's the case at the moment. (See "Chinook Winds" in the previous blog entry).

We've had a persistent weather pattern that has favored these warm, dry winds blowing, but the pattern can change just as quickly to one where we get storm after storm and wonder where the snowplows are.

Southern Colorado's long-term weather records show that we've done this before (weather tends to run in cycles), and we'll certainly do it again, with some cooler, wetter periods in-between.

In the meantime, enjoy the warm and wait for the storms (and remember that snowpack in the mountains is either right where we expect it to be, or perhaps even a little bit above that level).