Thunderation

Weather: Morning temperatures down to middle 20s Friday, two day after the sun angle code changed in The Old Farmer's Almanac; last rain 11/5/2013; 9:29 hours of daylight today.

What’s still green: Juniper, arborvitae and other evergreens, garlic, yucca, cholla and other cacti; leaves on Apache plume, roses, fern bushes, Oregon holly, hollyhocks, winecup mallow, dog violets, Saint John’s wort, vinca, coral bells, bindweed, oriental poppies, scarlet and blue flaxes, Dutch clover, sweet pea, bouncing Bess, moss phlox, snakeweed, anthemis, grasses.

What’s red or turning red: Raspberry, coral beardtongue leaves.

What’s grey or blue: Four-winged saltbush, snow-in-summer, pinks, pink salvia, catmints, baby’s breath, chocolate flower, golden hairy aster leaves.

What’s yellow or turning yellow: Cottonwood, weeping and globe willows, German iris, golden spur columbine leaves.

What’s blooming: Jupiter’s beard, broom senecio, chrysanthemums, tansy.

Bedding plants: Snapdragons, sweet alyssum.

What’s blooming inside: Zonal geraniums, aptenia.

Animal sightings: Small brown birds, probably goldfinches.

Weekly update: About the time the first fire started last spring, I began looking at the humidity levels every morning on the government’s weather website. I’ve learned two things.

Humidity levels just tell you how much water is in the air, which is interesting when the percentage falls below 10%. You don’t need it tell anything to tell you when the level is above 80%.

I discovered what’s important is not how much water, but where the water is coming from. The only moisture that matters is water moving in from some other area. Otherwise, it is coming from the ground and leaves. That’s not something they tell you.

The other thing I learned is that weathermen have standard ways of forecasting, so whenever they use unusual words or phrases they mean more than they are saying.

A week ago Saturday, 2 November, they said:

"A moist weather disturbance rolling east from the southern California coast to New Mexico will combine with a southbound plunge of Canadian cold air Monday to produce another round of wintry weather for northern and western New Mexico through Wednesday morning."

That all sounds a bit prosaic, although words like disturbance always sound so bureaucratically neutral. Then, they added:

"With some uncertainty remaining in the exact time and place of the collision between southern California moisture and cold Canadian air"

When the language gets dramatic - a la the clash of titans - beware.

Monday came, and so did the weather. Around 8:30 pm, there was thunder and lightening. It already had rained in Los Alamos, and thunderstorms were around Santa Fé. Nothing odd. I went to bed.

Sometime, and I didn’t look at a clock, thunder woke me. Not just thunder. A deep rumble that went on and on and on. So deep, it penetrated my body.

Half awake, I thought, but there’s no lightening. With that much noise, the room should be lit up. I fell back asleep.

In the morning, I looked up thunder in Wikipedia. Obviously there was something I didn’t know.

After the usual commonplace about lightening causing thunder - which it did not in the night - it went on to explain some mechanics:

"thunder must begin with a shock wave in the air due to the sudden thermal expansion of the plasma in the lightning channel. This heating causes it to expand outward, plowing into the surrounding cooler air at a speed faster than sound would travel in that cooler air. The outward-moving pulse that results is a shock wave."

More techy than I wanted, but I gather what happened, is that collision between warm and cool air forecast a week ago wasn’t some vertical confrontation. It was horizontal. That is, the warm air must have been riding over the cold air, rather like a bronco riding holding on. The differences in temperature must have caused the prolonged rumble as they passed overhead.

The next day’s forecast was equally obscure. NOAA predicted "patchy bands of rain," which is a good a description as there is for what passes for rain in this part of the country.

Then, they added, "ice pellets may fall out of some of the lower elevation bands." Not sleet, not hail, just bits of ice falling out of the atmosphere after that great collision. And they did.

Notes: Hazardous weather warnings for 2 November and 5 November issued by the National Oceanic and Atmospheric Administration’s National Weather Service.

Photographs: Cottonwood growing near a lateral ditch in town, 8 November. It must once have been farm land, but everything was cleared for some business. Then, that building was razed, leaving a smooth, concrete slab. Now the tree stands alone, dropping its leaves to protect itself. They must have fallen after the storms of Monday and Tuesday to lie so densely and undisturbed.