Native Plants, Habitat Restoration, and Other Science Snippets from Athens, Georgia

Sunday: 16 February 2014

The Great Ice Storm  -  @ 09:04:32

Before the earthquake on Valentine's Day Friday evening, we had the snow and ice storm on Wednesday, and Thursday morning.

The winter weather was supposed to have started on Tuesday, and indeed places even ten miles north had up to two inches of snow. For us, it was half an inch of rain, and we didn't quite hit freezing during the night. There was a large amount of variability, over small areas, in the form of precipitation in Round One.

For us,the real weather came in Round Two on Wednesday, when temperatures never went above freezing. There were dire warnings about power lines going down, fallen trees, and loss of power for days.

Most of the precipitation was in the form of ice pellets. We had some freezing mist, but the dreaded freezing rain did not hit us. Tree branches and power lines remained largely clear of ice, and were not weighted down. We never did lose power. I haven't noticed much in the way of newly fallen branches, much less whole trees.

Not so for a lot of folks in the Atlanta area, and south of us. The actual freezing rain that amounted to a real ice storm hit in those places, and there were a lot of power outages. I recall the number was somewhere between 300,000 and half a million. We just weren't particularly affected in the area roughly around Athens.

Early Thursday brought Round Three, with more dry ice pellets and a small amount of snow. We ended up at this point with 2.6 inches of a granular mix covering a layer of ice on the ground.

A little before noon, after the precipitation finally ended, I did a test drive up to the road to do a little practicing. We're at the end of the road, on a cul de sac with very little traffic, and indeed no one had yet driven on the road.

This has turned out to be a sort of standard photo. I've found versions of it at most of our snowfalls in the last few years.



I'm happy to report that the Honda CR-V does a great job on whatever mix it was on our long driveway. I didn't venture out to test the rest of our road. On Thursday, late afternoon, we had reports from a fellow firefighter that Wolfskin Road still had patches of ice, and meltwater flowing across it. Our access road that you saw in the first photo above quickly dips steeply downward, angles sharply, and then even more steeply upward. It's always been our main impediment to getting out, since it gets less sun and thaws a lot less quickly than most places.



Neighbors began appearing before I was really able to exit the driveway. I should mention that that 2.6" of ice pellets gave about 1.6" liquid. With the usual snow to liquid ratios, it would have translated to about a foot of snow had it actually been snow.



It seemed better to minimize the disturbance, for the skiers and sledders. After they departed into the background, I did sneak one pass around the cul de sac before returning home back down the driveway.



There were the school and other closures that made things easier and safer for everyone. University of Georgia took its cue from the primary and secondary schools and closed for Tuesday, a good call given how variable conditions were at that time. They quickly announced Wednesday would be closed, and then so would Thursday.


Saturday: 15 February 2014

Amateur Night Earthquake  -  @ 11:09:38

Eleven years ago, on March 18, 2003, at 1:04 AM, right here in my bed in Oglethorpe County, I was awakened by a little earthquake, the first I'd ever felt. There was a vibration that, for about five seconds, rumbled through the bed and rattled the windows with a distinct hum. That was a little more than a year before I started this blog, so it never appeared here except in the form of comments. I went to the computer to explore reporting possibilities, and discovered earthquake.usgs.gov. There I discovered that the earthquake was centered about 30 miles southeast of us, 3 miles deep, and (at the time) about a magnitude 4.4. Since then it's been downgraded to a 3.5. I was also fascinated in the listing of reports from other locations.

Last night, at 10:23 PM, I felt a rumbling vibration under the chair as I sat at the computer downstairs. I took off the headphones and called up to Glenn, "Did you feel that?" Indeed he had! Windows rattled for about five seconds, and rippled the surface of a glass of wine. We brought up USGS and entered in the information: yes, we were awake; yes, we both felt it; here's what the shaking was like; we were *quite* excited; no, there was no damage; and we did not move to a doorway, drop and cover, or run outside. We ran to the USGS website and had entered our info before the website had produced a preliminary presentation page.

As did 13,600 other respondants in 930 zip codes and 56 cities.



In the above figure, we're just above the little "a" in Athens-Clarke. Reports came in from Georgia, South Carolina, North Carolina, with a few from Alabama, Tennessee, and even Virginia.

Initial reports were of a 4.4 magnitude earthquake centered near Edgefield, South Carolina, somewhere around 60 miles east of us, and 3 miles deep. Not very exciting to those on the active margins of the West US coast, of course, but as a once in a decade event, pretty neat to us.

I took a look at the USGS response page. There were 301 responses from Athens-Clarke County, roughly 0.16% of the population. There were 24 responses from Oglethorpe County, including us, and amounting to somewhere around 0.17%. Augusta, GA, about 30 miles from the center, could only boast 342 contributers, again 0.17%. On the other hand Edgefield, SC, at the epicenter itself, managed 324 observations out of a population of 4750, or 6.8%, 40 times more than Athens, Oglethorpe County, or Augusta. Oddly, given its history, Charleston, SC, could muster only 44 reports out of 125,000 Charlestonians. These locations, including Edgefield's, averaged a 3 on the response scale you see above, generally a weak to light earthquake with no damage.

How then to explain the 40-fold difference in responses from the immediate zone compared to most of those 60 miles away? The intensity wasn't all that different. We don't get a summary of the length of time of the event, so I can't compare our 5 second duration with that of others closer. And we can't see when those responses were entered at USGS, but many of them were made hours after the event.

There were a few tweets from folks around Athens almost immediately, and of course I texted a couple of nearby acquaintances to ask if they'd felt it. Comments on a blog that features a few north Georgia readers began appearing, and apparently FaceBook featured quite a few posts almost immediately. Too Much Information appeared via the inevitable Valentine's Day Quake jokes. There must be some number of contributors who only learned of the USGS page later.

That repeated percentage of reporting from populations 30-100 miles away, amounting to about 0.16%, is kind of interesting too. It's just the number who reported, not the number who felt it. That number must be considerably higher, though I'm sure a lot of people didn't notice it at all. Maybe a lot of those who did notice it just didn't care all that much. But even so, *just* 1 in 600? When use of the internet in the US is now around 80%?

Glenn thinks, in an optimistic way, that the report rate of 1 in 600 is high. Certainly that 13600+ absolute number is great, and provides enough observational data to make that detailed figure above. And it's true that a lot, maybe even most of my acquaintances use the internet in only a minimal sort of way. They're not particularly adept at searching, nor do they show much interest outside of professional or social network use. Maybe Glenn's right.

Saturday: 1 February 2014

The Month of January  -  @ 17:26:21
It's The Month of January, Number 96 in a series, and therefore end the eighth year!

The word for January, in the eastern half of the country, was cold, but not unprecedented by any means, nor earth shaking. If you were outside of the eastern US, and paying attention, you knew about much warmer than normal temperatures in Europe, northern Asia, and record breaking high temperatures in Australia.

Still, for us, the average of the daily low temperatures this January was the 3rd lowest since 1920, beat out only by 1977 and 1940. Even the average mean daily temperature was the 4th lowest since 1920. Only peripherally related was the snowfall of January 28th, but we had less than an inch here, much less than that of Feb 2010, Dec 2010, and Jan 2011.

Nationally:

Here are the usual temperature anomalies products, at the National Weather Service Climate Prediction Center. Displayed are the high and low temperature anomalies.

Click on the image for the high and low anomaly graphic on a new page:



We switched from a warmer than usual December to a colder January here in the southeast US, while much of the western US was as much warmer than usual.

It's as stark a picture as any - warmer than usual sharply gave way to colder than usual across a line nearly bisecting the US from north to south.

We find the National Weather Service Climate Prediction Center's precipitation plots here.



Almost as stark was the level of dryness over much of the country. California's extreme drought began to make its way eastward through much of the southwest into the south. There was a continued deficit of precipitation in the central plains. The northwestern states including Montana, Idaho, Wyoming and parts of Utah and Colorado got normal to above normal rainfall, which was the fate of a lot of the northeast as well.

For the Athens, GA area:

Below is my usual daily rain/temperature plot visualizing the changes in temperatures and precipitation. The spiky lines are temperatures recorded roughly ten times a day, and the lighter blue columns are Wolfskin rainfall measurements.



The black line is the normal average daily temperature, and you can see that we're now starting to creep upward. We only had a few scattered days of average temperatures, usually associated with modest amounts of rain. We had three periods of much colder than usual weather, the first occurring around Jan 7, and that was the most intense of the three. It was the last cold spell that brought the snow and ice to the southeast a few days ago, but as you can see the liquid phase of the precipitation was actually quite small.

Below in blue are the daily low record temperatures for Athens, GA. Red show last year's daily averages (a much warmer January!) and green are for January 2014. The black dots are unconnected daily averages for 1990-2011, and give you an idea of the spread.



On average, we were cold in January. The Athens area mean temperature during January was 6.4 degF below the normal 43.2F. Even so, we only matched one low temperature record of 7 degF, on Jan 7, where the green hits the blue.

We had only 2 days more than 1 standard deviation above normal highs (average is 5.2 days), and that reflected the colder month. In contrast, we had 12 nights with temperatures more than 1 standard deviation below normal lows (average is 4.2 nights). It was definitely a colder month by this count.

Let's look more closely at the breakdown in temperature ranges in January. Our average low was 25.6 degF, 7.5F below the normal monthly low, and the average high for January was 6.4F below the long term average high. Both days and nights were colder, but nights were more anomalously cold than days.

The monthly histogram below shows the breakdown of high and low temperature range counts from January 1948 on. The error bars are just plus/minus one standard deviation, which I arbitrarily set as the limits outside of which are "significantly" anomalous.



The high temperature events fall on or within the error bars, but the two coldest ranges just barely scrape significance. The low regime shows the normal number of 30-40 degF lows, more or less, but there's a significant loss of warmer nights (>41F) shifted into the much colder nights (20F and below).

Below is the monthly accumulation of rain in Athens, GA. The river of peach is the long term standard deviation of all the daily black dots in the last 15 years, and the red line is the daily cumulative average. We're the green line this year, and for almost half the month it cradled that surplus of blue above the one standard deviation mark.



Almost all our rain was due to a nearly four inch rainfall over the period January 9-11, just after the first cold spell. There was a fair amount of variation in this rainfall, and Athens got more than we did. With all the other rains, the official Athens rainfall in January was 4.68 inches(4.05 inches average for January). Out here in Wolfskin we had only 3.56 inches.

We had virtually no rain in the last three weeks of January, and with windy, extremely dry air most of the time experienced a lot of brush fires. On several days Oglethorpe County VFDs were being called to as many as three outbreaks per day.



Prognosticator stuff:

What is the prognosticator telling us?

First, for us here in the southeast, it had been accurate over the last five months for temperature and precipitation, but its prediction of drier and warmer in the last half of December certainly failed for rainfall predictions. That mushy success rate continued in January. We did get a big rain, followed by a dry period, but the normal to warmer weather that was predicted for January was not correct.

So for what it's worth, as of 1 February, we'll have a higher than normal chance of precipitation for the next month, then an equal chance of normal precipitation in the early spring.

Temperature-wise, it tells us in the Southeast that we can expect a couple of more weeks of colder temperatures, which coupled with the above increases our chance for more snow (!). After February, there is a higher probability of warmer than usual weather in March and April.

There is also seasonal drought outtakes on that page. Take a look at the best 3-month guess ahead for your own region!

ENSO stuff:

The folks at CPC have a version of PDF or HTML that is much different from their previous presentations, but at least it's there and the link isn't broken.

As of 27 January, ENSO neutral conditions continue, and are expected to remain neutral, now through the Northern Hemisphere summer. We've remained ENSO neutral now for 21 months. The last time we had such a lengthy period without an El Niño or La Niña must be at this point in the 1990s.

NOAA's Monthly State of the Climate product for December is available. Winter storms in New England, top 10 cold temperatures in the northern tier of states, and drought in the Pacific states, especially California which just now completed its record driest year.

You'll find that and more in the preliminary annual report for 2013 regionally, nationally, and globally. NOAA will add to and modify it over the course of the next few months.



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