Unusual cold weather inspires some meteorological education
Graupel accumulates on soil and plants Wednesday in northern Carmichael.
The white stuff falling from the sky looked like hail, but it didn't bounce. When I picked it up, the little pellets were soft and mushy, not hard. It didn't seem to be snow, either. What was this?
The National Weather Service in Sacramento came to the rescue with the answer: It's graupel. (That's a Germanic word, a diminutive of Graupe, meaning "pearl barley," Merriam-Webster says.)
On its Facebook page, the NWS explained: Graupel is composed of snowflakes that collect supercooled water droplets on their outer surfaces. It forms "when it's very cold aloft but there are above-freezing temperatures at the surface."
If it's soft/wet, it's graupel. If it's hard/solid, it's hail, the weather service says.
Hail, by the way, is defined as frozen raindrops of ice from thunderstorms. It forms "in strong upward winds in thunderstorms" then falls to the ground before melting.
Sleet is another thing: At ground level, sleet is only common during winter storms when falling snow hits a layer of warm air and starts to melt. The resulting droplets hit a deep layer of cold air just above the surface and refreeze into sleet before hitting the ground.
Having read up on graupel, I went down a meteorological rabbit hole of cold-weather terms. (I'm a California kid -- I didn't grow up knowing this stuff.) Here are some of the more interesting ones I found, thanks to the National Weather Service, the National Severe Storms Laboratory and other weather sources.
-- Freezing rain. Subtly different than sleet, it occurs when snowflakes descend into a warmer layer of air and melt completely. When these liquid water drops fall through another thin layer of freezing air just above the surface, they don't have enough time to refreeze before reaching the ground. Because they are “supercooled,” they instantly refreeze upon contact with anything that that is at or below 32 degrees F, creating a glaze of ice on everything. Side note: A significant accumulation of freezing rain lasting several hours or more is called an ice storm.
-- Ice fog. This is a type of fog consisting of fine ice crystals suspended in the air; it's apparently rare except for the coldest parts of the world. More common is a freezing fog, which occurs when liquid fog droplets freeze to surfaces.
-- Pogonip. Another term (of Native American origin) for ice fog.
-- Sea smoke. This occurs when freezing winds flow across warmer water, causing fog to rise up and create a swirly wall. Sea smoke can resemble a giant wave.
-- Snow devil. Like a dust devil, it involves swirling air. It forms when snow is raised from the ground in the form of a whirling column of varying height with a small diameter and an approximately vertical axis. Also called a "snownado."
-- Thundersnow. According to the NWS, this is caused by an intense updraft that creates hail and super-cold water droplets, leading to snow being the primary precipitation rather than rain.
Stay safe and warm, gardeners, whatever weather you encounter this weekend. The garden will survive.
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Dig In: Garden Checklist
For week of June 4:
Because of the comfortable weather, it’s not too late to set out tomato and pepper seedlings as well as squash and melon plants. They’ll appreciate this not-too-hot weather. Just remember to water.
* From seed, plant corn, pumpkins, radishes, melons, squash and sunflowers.
* Plant basil to go with your tomatoes.
* Transplant summer annuals such as petunias, marigolds and zinnias.
* It’s also a good time to transplant perennial flowers including astilbe, columbine, coneflowers, coreopsis, dahlias, rudbeckia, salvia and verbena.
* Let the grass grow longer. Set the mower blades high to reduce stress on your lawn during summer heat. To cut down on evaporation, water your lawn deeply during the wee hours of the morning, between 2 and 8 a.m.
* Tie up vines and stake tall plants such as gladiolus and lilies. That gives their heavy flowers some support.
* Dig and divide crowded bulbs after the tops have died down.
* Feed summer flowers with a slow-release fertilizer.
* Mulch, mulch, mulch! This “blanket” keeps moisture in the soil longer and helps your plants cope during hot weather.
* Thin grapes on the vine for bigger, better clusters later this summer.
* Cut back fruit-bearing canes on berries.
* Feed camellias, azaleas and other acid-loving plants.
* Trim off dead flowers from rose bushes to keep them blooming through the summer. Roses also benefit from deep watering and feeding now. A top dressing of aged compost will keep them happy. It feeds as well as keeps roots moist.
* Pinch back chrysanthemums for bushier plants with many more flowers in September.
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