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

Saturday: 7 September 2013

The Month of August  -  @ 08:56:25
It's The Month of August, Number 91 in a series. Rainy conditions beginning in June accelerated in July and continued through August. A relatively cool summer continued for us in the southeast.

Here are the usual temperature anomalies products, at the National Weather Service Climate Prediction Center. Displayed is the mean temperature anomaly for August.

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

Much of the eastern US went from weakly warmer than usual in June to considerably cooler in July, and that situation continued in August. Much of the West continued warmer than usual, except for parts of the extreme southwest.

(The high and low anomalies graphic shows that nights were warmer than days were cool. Again, cloud cover, rain, and high humidity kept us cooler during the day, but prevented cooling at night. This was also distinctly true for the West, by whatever means.

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

The Pacific Northwest got some relief from the very dry weather of July. The pattern of dry and wet is very scattered and broken. The Midwest continued drier than normal in August, while the most of the Southeast continued wetter than normal. Rain did spill westward though, into the previously dry southwest. OK and KS once again received at least normal rainfall and a surplus in many parts of the states, but dry weather began to creep northward into NM and TX.

For the Athens, GA area:

Below is what I've finally come up with as a daily rain/temperature plot. The spiky lines are temperatures recorded during the days, and the lighter blue bars are Wolfskin rainfall measurements.

The black line is the normal average daily temperature, and you can see that we're distinctly on our downward fall toward autumn.

Two outstanding features above: the daily highs seldom went above 90, and the rainfall that began in June continued in August, with two events over an inch to add to the many such this summer. I believe we broke records for lowest high temperatures midmonth, but did not quite break the record lows during the same period. We did match the record low of 1967, at 60 degF on Aug 17.

The average monthly temperature for August was 76.9 degF, significantly below the 30-year average of 80.2F. Again, our average high was lower than usual by nearly 5 degF, and our average low was lower than usual by just about a degree.

So it should come as no surprise that we had, again, 0 days more than 1 standard deviation above normal highs, and 0 night with temperatures more than 1 standard deviation below normal lows. We did, however, have 9 days that with highs more than 1 standard deviation below the normal high.

The monthly histogram below shows the breakdown of high and low temperature range counts from August 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.

Despite the distinctly cooler average temperatures in August, the histogram shows little distinct deviation in numbers of days within the indicated ranges. I think we have run into a rarely encountered weakness in this presentation: The highest temperatures in August rarely went over 90F, and that is my cutoff for that range. So much of the 90-99 column are 90F temperatures that could have gone into the 80-89 column, had I chosen my ranges just slightly differently.

The figure below shows the Athens precipitation data which are official for our area. As usual the green line shows our actual rainfall, the red shows the average accumulation expected. The black dots are rainfall over the last 22 years, and the river of peach shows the standard deviation.

For the third month in a row, we had the welcome blue of surplus rain, greater than one standard deviation, although only for a day or two. The green line is Athens official, ending up at 5.68" for August. Here in Wolfskin we had 5.46". That now puts over the annual average rainfall.

Our total rainfall this Jun/Jul/Aug out here was 25.86", more than half our usual annual rainfall. Overall, we have stayed above average rainfall all year since mid-February.

Prognosticator stuff:

What is the neat prognosticator telling us? For us here in the southeast, it has been accurate over the last two months for temperature and precipitation. As of 6 Sep, it tells us that we can expect normal to higher than normal precipitation over the next three months. Temperatures should be normal from here on out.

Over the next couple of weeks, though, temperatures will become increasingly above normal for much of the rest of the US.

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 Sep 3, ENSO neutral conditions continue, and are expected to remain neutral throughout the Northern Hemisphere fall. We've remained ENSO neutral now for over a year. The last such lengthy period was 10 years ago, 2003-2004. You can't use an El Niño or La Niña to explain extreme weather this year.

NOAA's Monthly State of the Climate product for July is available. And last year's annual report for 2012 regionally, nationally, and globally is also available.

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