What a wild week of weather the US has experienced. But signs of spring are popping up. Europe is back to above normal temperatures, and the few residents of northwest Australia get a tropical cyclone.
Let’s go Around the World.
Yeti, Iceberg, Dill, Neptune, Octavia. Who Can Keep Track Of The Names?
Decoded Science has consolidated Extreme Weather Events Iceberg Lettuce and Dill into a single ongoing weather event — Yeti. It saves space and is more expressive.
The Weather Channel insists on naming every foul weather entity a ‘storm,’ so they now have Neptune and Octavia. Until TWC can define ‘storm,’ Decoded Science thinks it’s better just to name the longer-term events.
Yeti is characterized by a displaced polar vortex with an embedded powerful jet stream around its periphery. Stormy weather is possible anywhere along the axis of the jet stream.
Northeast Tries To Dig Out But The Snow Keeps Coming
For several weeks, the vortex associated with Yeti has been centered over eastern North America. Storms have particularly impacted Boston and northern New England. Boston has surpassed every record available for the breaking, including snowiest all-time month.
Interestingly, February’s 46 inches and counting surpasses the old record set in January, 2005; the two snowiest years in 142 years of record-keeping have come in the 21st century — possibly a derivative effect of global warming, which is forecast to produce more extreme weather events.
The latest incarnation of Yeti will mostly bypass New England and concentrate on the mid-Atlantic after blanketing the midwest with snow and the deep south with ice, but Boston could end up with a couple of inches of snow.
Yeti’s Axis Of Action Shifts South
As the polar vortex has shifted south in the last few days, Yeti has taken aim at the Ohio Valley and the Deep South. A significant snowstorm has dropped up to a foot of snow on parts of Kentucky and Ohio, but the most serious consequesces of Yeti are from ice.
How Does An Ice Storm Develop?
Freezing rain storms are not common, but they can cause major damage due to superslick roads and toppled power lines. The specific ingreients are:
- Cold air at the surface — lower than 32 degrees.
- Warm air above the cold — higher than 32 degrees.
- The right amount of each.
Freezing rain scenario: Precipitation forms as snow at high altitudes, falls into the warm layer and melts, then freezes on contact with the ground. If the cold layer is too thick, the raindrops will re-freeze into sleet before they hit the ground; if the warm layer is too thin, the snowflakes will survive unmelted to the ground.
The South-Central And Southeast US Are Prime Spots For Freezing Rain
Cold air masses frequently invade the US from Canada in the winter. At the southern extent of a cold air mass, the temperature is just below freezing and the cold air wedge is shallow. The area from Oklahoma eastward to the Carolinas is close enough to the Gulf of Mexico so that when warm air streams north and rides over the cold air at the surface, freezing rain will fall.
The current flows of cold and warm air masses have created the perfect conditions for freezing rain, and damaging amounts have fallen from central Tennessee eastward to North Carolina. The primary harm comes from ice-coated tree limbs. When the thickness of the ice exceeds 1/4 inch, the added weight can cause the limbs to break and fall on power lines.
Ice-coated roadways and sidewalks are also dispruptive to orderly and safe movement of quadripedal vehicles and bipedal animals. Authorities reported 189 motor vehicle encounters of an unpleasant kind in Nashville alone on Monday.
Ice will continue to accumulate today in North Carolina. No doubt the 300,000 already without power in the south will be joined by others.
Crocuses Bloom In February In The Northwest
As the jet stream dips south in the east, it bulges north in the intermountain west and the west coast. While the the east suffers extreme cold, the West experiences record warm temperatures. Unseasonal blossoming of spring flowers dots the landscapes of Washington and Oregon.
The new push of Yeti’s cold air will reach the Rockies but not be able to cross, as warm air holds its ground. Denver and Cheyenne will be on the battlefront, with temperatures seesawing from well below freezing to the fifties.
Decoded Science will have more on the western heat wave on Friday.
Tropical Cyclone Lam Will Strike Australia
A small tropical cyclone, Lam, has developed over the Arafura Sea between Australia and Indonesian New Guinea. A tropical low in this part of the world has a hard time getting anywhere without smacking into a cyclone-killing land area.
Lam could reach category two hurricane strength (100 mile per hour winds) before making landfall in the Gore Peninsula, a relatively uninhabited part of northwest Australia. A buaxite mine and a few thousand people could be minimally affected before Lam blows itself out.
The Australian tropical cyclone season runs from November to April, but the most intense storms tend to come near the beginning or end of the season. At 84 degrees, the water is warm enough to support powerful cyclone formation. Last year, two category five cyclones formed in March.
Above Normal Temperatures Return To Northern Europe; Southern Europe Remains Rainy
After a bout of unpleasantly cold and windy weather (Severe Weather Event Courgette), northern European weather has reverted to last winter’s pattern of generally above average temperatures:
- Berlin has been above normal since February 7, and the forecast calls for warm temperatures through the end of the month.
- Moscow has been above normal since early January and is forecast to stay warm through early March.
- Madrid had a recent cold spell, but has been warm for five days and is forecast to remain above normal through mid-March.
- Oslo has been above normal for the last ten days and is forecast to remain warm throgh early March.
A southern branch of the jet stream is keeping southern Europe warm but rainy. The severe flooding that caused 82 deaths in Albania in the first week of February has subsided, but the weather pattern still indicates a threat of storms across southern Spain, Italy, Greece, Albania, and Bulgaria.
While residents of the east coast are sick of winter, westerners have hardly noticed that there was one. Weather patterns seem to be stuck in place, and there is little evidence that things will change any time soon.
Is it global warming that has gummed up the weather gears? Extreme weather is consitent with models of the atmosphere given increased greenhouse gases.
So what evidence of change do you see?