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April ended with a tornado and May began with a snowstorm for our region’s next-door neighbors.
That may seem like odd – even backwards – timing, but an atmospheric traffic jam over North America has at least temporarily thrown the normal seasonal progression off kilter in our region and through much of the eastern half of the nation.
As projected here a week ago, April indeed finished without a tornado report in the Cardinal News coverage area, roughly west of Interstate 85 and south of the James River, but not far to the east, a destructive tornado ripped into one of the state’s largest metropolitan areas late Sunday.
In Virginia Beach, 115 homes were damaged by an EF-3 tornado with winds up to 145 mph, traveling along a 4.5-mile-long path that was up to 350 yards wide. There was some dramatic video of the tornado posted on social media.
Then, by Monday evening, waves of heavy snow were blowing over the high terrain of eastern West Virginia, with some amounts around half a foot by early Tuesday at elevations above 4,000 feet.
A little bit of this snow managed to work into the western fringe of Virginia, mostly at high elevations, but most of the moist flow off Lake Michigan was wrung out over the Allegheny Mountains before reaching the state line. Chilly winds, however, kept temperatures below normal for early May, mostly 40s and 50s, some 60s with sunshine, over much of Southwest and Southside Virginia.
Additional showers, some of those snow showers at higher elevations, were blowing through West Virginia and into western Virginia early Wednesday. Some icy graupel mixed with rain at Blacksburg, and snow totals topped a foot on some eastern West Virginia high ridgetops by Wednesday morning.
This was all the result of a strong upper-level low spinning over the Great Lakes, only slowly wobbling eastward, affecting our weather much of this week.
Something called an “omega block” has been at play this week in keeping it breezy and unseasonably cool across our region, downright cold in the higher mountains.
Omega is the last letter in the Greek alphabet, shaped like this: Ω
You might see something resembling that shape in this map of upper-air flow 6-7 miles up (black line added for clarity), taken from the initialization of Monday’s 18Z GFS model run. (Initialization being the model’s interpretation of the current atmospheric flow, based on thousands of data inputs at 18Z, or 2 p.m. EDT).
The omega block comes about because the upper air flow gets crinkled, for lack of a better word, as low pressure troughs dig in on either side of a high-pressure ridge in the middle.
None of the three features can make much progress as the jet stream flow spools around them rather than pushing any of them anywhere fast. This week for our region, it’s the big upper-level low pinwheeling over the Great Lakes affecting our weather most, with a constant flow of unseasonably cool wind out of Canada around the low and eastward toward us.
This is also part of a broader Northern Hemisphere traffic jam behind blocking high pressure near Greenland, the negative phase of the North Atlantic Oscillation, that much-desired phase for snow lovers that only flashed its presence for a few short windows in the mostly warm and nearly snowless 2022-23 winter.
As omega blocks go, the high pressure in the middle isn’t exceptionally strong, and we’ll see this pattern gradually begin to erode by late this week with more seasonably warm temperatures by the weekend – and quite possibly above normal by next week.
AN EL NIÑO SUMMER?
Occasionally, the question arises about what El Niño might mean for our summer weather.
The potential effects of El Niño and La Niña are usually discussed in the context of the cooler end of the calendar, from fall to spring. We see more dynamic jet stream patterns in the cooler months, which tend to express downstream effects of various climatic phases more than the sluggish flow of summer patterns.
We are at that point in which the strip of the equatorial Pacific waters is obviously warming but it hasn’t been warm enough, long enough just yet to be officially called an El Niño.
It’s a little like the discussions and debates that develop over when a recession has begun – the economy can be in a slide for months before an official “recession” has begun.
So what does it mean for summer that the equatorial Pacific is moving toward El Niño?
Not much that is easily discernible.
Correlations with winter weather are already pretty loose. They are even looser with summer weather in our region.
A quick review of 19 summers since 1950 with either an ongoing or developing El Niño at the four official major climate stations recognized by the National Weather Service found perhaps one tendency that might be worth mentioning.
Not many El Niño summers are among the top few warmest on record, based on average temperature across the entire June 1-August 31 meteorological summer season, in our region. 1987 appears to be the big exception, ranking second to four warmest since 1950 at Roanoke, Lynchburg and Blacksburg. (Danville had 42 days of missing data that summer.)
That’s not to say there were not some extremely hot periods among some of the other El Niño summers, such as July 1977 with multiple 100-degree days across much of the region and the Aug. 19-21 period in 1983 that reached 104 or 105 at least once at Roanoke, Lynchburg and Danville. But summers with El Niño at least starting to cook haven’t tended to be among the hottest on average from start to finish in Southwest and Southside Virginia.
Several El Niño summers are among our coolest on record, particularly 1972, Roanoke’s coolest on record and among the half-dozen or so coolest at Lynchburg, Blacksburg and Danville. It’s also among the 10 wettest summers at each of those sites except Danville, owing largely to the June effects of Hurricane Agnes’ remnants that caused near-record flooding on many regional rivers.
Rainfall totals for our El Niño summers have been all over the map, including some of the wettest and driest summers and many in the middle.
So, really, trying to pull anything out of previous El Niño summers to guess what this one might do is grasping at straws. If it fully manifests as expected, El Niño may be a little more helpful as a guide when we get back to winter, but only against the backdrop of several other climate oscillations.
SOAKING RAIN
Speaking of wet and dry, late last week and the weekend brought two rounds of rainfall onto what had been pretty dry soil over much of our region, with late Thursday into early Friday particularly delivering a widespread soaking unlike any we’d seen since mid-February.
Most locations in Southwest and Southside Virginia received 1 to 3 inches on Thursday night into Friday.
Some totals that exceeded 3 inches in the first round of rain through midday Friday, reported to the National Weather Service office in Blacksburg, listed by nearest city, town or community (multiple reports for some locations), include:
· Forest, Bedford County, 4.11 inches
· Amherst, Amherst County, 3.60-3.87 inches
· Woolwine, Patrick County, 3.28-3.70 inches
· Bedford, Bedford County, 3.10-3.55 inches
· Stuart, Patrick County, 3.44 inches.
· Just southwest of Lynchburg, 3.30 inches
· Hardy, Franklin County, 3.16 inches
· Troutville, Botetourt County, 3.13 inches
There is no obvious next soaking rain yet, just some periods of shower chances on Saturday (of course) and early next week as the temperature begins to warm back up.
Journalist Kevin Myatt has been writing about weather for 19 years. His weekly column is sponsored by Oakey’s, a family-run, locally-owned funeral home with locations throughout the Roanoke Valley.
