Developing cool snap will be broader than it is deep for SW Virginia
By Saturday morning, a Canadian cold front will push through western Virginia, introducing the leading edge of an air mass that orginated in the Arctic Circle earlier this week and got squeezed southward by high pressure systems over the western U.S. and over Greenland. It’s the way cold air is frequently delivered to us in winter, but of course then, it is traversing thousands of miles of snow-covered terrain or at least cold ground on its way. Not in August. Also related to the typical course of air masses in August, the front will stall just south of our region across the Carolinas the next couple or three days. As disturbances slide southeastward in the northwest flow, a wave or two of low pressure may develop along the front and fling some moisture back across us for clouds and showers. These impulses are difficult to time, but perhaps late Sunday into Monday may be a period for at least a somewhat enhanced chance of rain. One effect of the clouds and showers will probably be that we will not see the kind of especially cool low temperatures we might have with clear, crisp, calm nights. There may be some degree of cooling into Sunday morning, and perhaps again Tuesday and Wednesday morning, that would allow many spots to dip into the 50s. But the clouds will also prevent daytime warming, and with limited sun into an air mass from Canada, it’s quite possible highs will not reach 80 on one or both days this weekend, even in Roanoke. The Hydrometeorological Prediction Center goes even further on Monday, projecting a high of just 74 for Roanoke (inset map at left), which would be 12 degrees below normal. While we may not challenge upper 40s/low 50s record lows in Roanoke or mostly mid-upper 40s record lows for Blacksburg with this cool air mass, there is no sign of a significant warmup anytime soon, and the air mass may even be reinforced again later this week. A prolonged period of below-normal high temperatures, with below-normal low temperatures on some mornings (normal high/low is 86/65 for Roanoke, 82/59 for Blacksburg) appears to be on tap for Southwest Virginia, shaving decimal points off what may not end up as even a top 10 hot summer that was so extreme at its peak.
August 17, 2012 - 10:28 PM
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I want to say I heard a few random thunder rumbles a while ago. Perhaps I dreamed it. It’s all quiet now except for the crickets.
Kevin, 2 or 3 days ago you mentioned that there has not been a major (Category 3 or more) hurricane to make a US landfall since (I think you wrote) Hurricane Wilma in 2005. Wow. But wasn’t that the only year in which the Greek alphabet was used? And how many major hurricanes made US landfall that year? Obviously Katrina was one, but I think that were at least two others …. Talk about “feast or famine.” Or maybe more a more appropriate phrase would be “feast and flood” for that incredible tropical storm season.
Kevin, this summer may serve as a good example of what you were discussing in the previous post’s comments. Trying to assess overall patterns can be very difficult even with the data we have available now. It can be very dependent on the perspective, i.e. how long a time period is being looked at, how are the extremes factored in, etc. Trying to do this over even longer periods is not easy, especially since we only have data for very recent times. I do not know if it is true, but I have read that our conception of Christmas being a period of snow cover dates back to the 1800′s when that was far more common that it is now. Even as far south as the carolinas it was not uncommon for winters to be cold enough for ponds and lakes to freeze over. If that is true, it certainly would appear we are in a warmer time peroid overall.
Doug:
In 2005, Dennis, Katrina, Rita and Wilma were all Category 3 at U.S. landfall (Katrina, Rita and Wilma were Cat 5 before landfall). In 2004, Charley was Category 4 at landfall, and Ivan and Jeanne were Category 3. So there were 7 major hurricanes in just 2 seasons, plus 3 other lesser hurricanes that made landfall (Frances at Cat 2 in 2004; Gaston in 04 and Cindy in 05 were originally considered tropical storms but later upgraded to Cat 1 hurricanes) and 2 others that scraped the Outer Banks without making landfall (Alex in 04, Opheila in 05). So those 2 years were extraordinarily busy for the U.S., and the time since has seemed like a balance for that.
It’s also of note that all of those major hurricanes except Rita (plus Category 2 Frances) hit Florida (though Katrina was only in the early Category 1 stage of its development when it did so).
Trevar: Dates vary some, but the period from 1500-1850 or so is often called the “Little Ice Age,” a decidedly cold period in much of Europe and North America. There is a disagreement among scientists about whether the warming out of the Little Ice Age into the 1900s was entirely a natural phenomenon or whether it was at least partly related to the early stages of increased carbon emissions with growing industry.
Global/national temperatures in the past century showed a notable dip in the middle part of the century, 1940-1980 or so, after being hot early and rocketing upward after 1980. Roanoke’s annual and 10-year average temperatures clearly show this same pattern, too. I’ll get to that in Weather Journal eventually. (Derecho/heat wave/personal events completely sidetracked my plans to do local historical climate analysis through usually slow summer months.)
Thanks for the news about the Doppler – I guess the sledgehammer trick did work. Glad to help out. LOL!
No rain of any significance up here on the ridge last night. Yes, I hate to say it but we could use a tropical system coming from the southeast to give us some rain. Those fronts from the west-northwest do not pan out and just jump the mountains. I am starting to call them Blue Ridge Jumpers. They are a lot like some of the systems we get in the winter.
OK, one more comment about the global warming issue. I read Michael Crichton’s “State of Fear” book about 7 years ago (Copyright 2004), and it is chock full of graphs and charts and data, nearly all from NASA and NOAA. So he used official govt. data from those organizations, not from an individual scientist or small group of scientists. I encourage anyone who is truly open-minded to at least get their hands on a copy of it and look at the graphs on pages 84-88. Those graphs track both global and US temperatures (using both annual means — which vary greatly — and 5-year means, which are more meaningful) and show what changes temps have undergone as the decades passed. From those graphs it is clear that global temps have risen overall since 1880, but the rise has NOT been at all steady. Overall almost flat from 1880 to about 1920 (a slight rise), then a much sharper rise through 1934 and perhaps one can argue to about 1940, then a fairly sharp decline through at least 1970, such that global temps in 1970 were about the same as they were in the mid-1920s. Then the almost steady rise. Huge questions are whether the drop between 1940 and the 1970s was an anomaly, or whether the current rise is just part of a much longer period of roughly 40 years of rising temps followed by 35-40 years of cooling. A couple of those graphs also compare temperature changes and Carbon Dioxide levels both over the entire 1880-2000 range and during the 1940-1970 period, when temps were decreasing both globally and in the USA (the temps continued to drop in the USA throughout the 1970s). Amazingly, CO2 levels rose continuously throughout both periods (except for the World War 2 years, when they were flat). So that calls into question very much the alleged direct relationship between CO2 levels and the warming effects of CO2 levels on the Earth’s temperatures.
Read that book and form your own conclusions/opinions.
This “new” air mass has not delivered in lowering the humidity. Very humid day here in NRV. And, forecasted lows for the next seven days go no lower than 58 (the normal low for Blacksburg this time of year is 59 or 58). Was really hoping the call for lows in the 40′s would materialize, but it looks like we will do no lower than what is actually normal for August.
Kevin, it is quite a pleasant summer day here in Christiansburg. I’m hoping it doesn’t rain when I go to Lane Stadium to watch the scrimmage. I see clouds are starting to form into rain clouds. Any indication there may be rain shower this evening?
This morning’s lows were never expected to be that cool, Mike, and the humidity for today is not unexpected, either. It does look like clouds/humidity may hold up some of the lows as is discussed above. Enjoy your sub-80 highs over there most of the next week.
I’m gonna be off on my guess of 54 Roanoke and 49 for Blacksburg for coolest temps I made a week ago. Still wouldn’t be surprised to see something like mid 50s for Blacksburg Tuesday or Wednesday morning.
There may be just enough warmth and humidity, with cooler air aloft, for a few scattered showers/storms this afternoon, Trevor. Lane Stadium sometimes seems like a magnet for this kind of stuff during preseason/early football season.
HPC has scooted the half-inch line on rainfall over next 3 days (mostly late Sunday/early Monday) to about Roanoke and the Blue Ridge.
http://www.hpc.ncep.noaa.gov/qpf/d13_fill.gif
Trevor..
Our conception of a snowy Chtistmas
may not have to do at all with the lower
48..It may have to do with the snowy
Northern Europe where many of our ancestors
and culure comes from.
Think Charles Dickens.
…Just a side (musical) note..and weather trivia.
The Stradivarius Violin came about as a result
of the European Ice Age and the compression of growth rings of
Spruce and Maple (google Stradivarius)
*** A more modern theory attributes tree growth during a time of global cold temperatures during the Little Ice Age associated with unusually low solar activity of the Maunder Minimum, circa 1645 to 1750, during which cooler temperatures throughout Europe are believed to have caused stunted and slowed tree growth, resulting in unusually dense wood.[23] Further evidence for this “Little Ice Age theory” comes from a simple examination of the dense growth rings in the wood used in Stradivari’s instruments.[24] Two researchers – University of Tennessee tree-ring scientist Henri Grissino-Mayer and Lloyd Burckle, a Columbia University climatologist – published in the journal Dendrochronologia their conclusions supporting the theory on increased wood density.[25]
Kevin pointed out something very interesting to me about a possible (major?) contributing factor to the cooling period from 1940 through the 1970(s?). Fallout from nuclear explosions. Not only from Hiroshima and Nagasaki, but from numerous nuclear bomb explosions by the U.S. (such as at Bikini Atoll in the South Pacific, and possibly some in the desert of Nevada, although most of those in later years were underground “tests” I think) and by the Soviet Union in Siberia. Those in the late ’50s and ’60s were gigantic, H-bombs. All those “particulates” in the atmosphere may have had a major or at least substantial influence in retarding sunlight from heating the Earth and especially the oceans during those decades. Hmmmmm …
Wow. Just did a Google search on Nuclear Explosions 1945-1980, and a website “nap” (National Academies Press) has as one of its tables a listing of 543 nuclear explosions during that timeframe, with a megaton yield of 440. 219 by the Soviets, 187 by us, and a few more by France (45), China, and the UK.
Back to August 2012. The CPC computer is not following the previous outline of a cool 2nd half of August. Here are the links from today’s strictly computer-generated maps.
6-10 day: http://www.cpc.ncep.noaa.gov/products/predictions/610day/index.php Nearly all of Virginia is in the white “Neutral zone” for temps, but we are sandwiched between two regions of warmth, the Northeast and the Southeast. Nearest blue on the map of the U.S. is in Iowa. All but far SW Virginia is in the pale green for 33% chance of being wet, which is nice.
8-14 day: OUCH! http://www.cpc.ncep.noaa.gov/products/predictions/814day/index.php All of Virginia is in the 33% chance of being warm, with 40% areas again to our NE and south. Again a 33% chance of being wet. Looks like I may possibly escape delivering mail in 90-degrees during the last week of August.
Did anyone happen to look at those CPC outlook maps yesterday? I wonder if they showed similar maps, or whether the computer (today) is striking out into “new territory.”
Fears of “nuclear winter” were all the rage in the 1980s. With so many above-ground nuclear tests in the early Cold War era (there were more underground tests later), it would have contributed to particulates in the air which could have helped block some sunlight. Of course, industry at the time was emitting a lot too.
I really think that the mid-20th century temperature dip was primarily a natural phenomenon that perhaps could have been augmented by some practices of the day. Kind of like the Dust Bowl — a natural pattern of heat and drought related to shifting mid-upper air currents, augmented by bad farming practices that have largely been corrected in the decades since. That’s generally the way I see weather/climate patterns — natural first, possibly augmented/intensified/modified by large-scale human-related factors. That’s why I generally think global warming might be adding a degree or two to some heat waves, but is not a core cause. There are well-meaning and knowledgeable scientists who agree with that assessment (NOAA, for instance, declaring in a report that the March warm spell as 90 percent natural caused) and others who disagree in favor of entirely natural causes or more influence by manmade causes. The discussion is far more interesting and diverse than the politically charged sound bites that dominate it in much of the media.
12Z GFS blasts Wilmington NC with a hurricane on Aug. 31
http://tinyurl.com/cdogaux
There is enough repeated support on multiple models to suggest a western Atlantic tropical system is something to keep an eye on as we near the end of August … but of course any specific path/strength is completely outside the resolution of the long-range models.
The dew point finally sank into the low 50s for Roanoke — but that only helped push the high to a near-normal 85 today with lots of sunshine. Officially 79 today at Blacksburg.