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

Tuesday: 4 June 2013

The Month of May  -  @ 07:36:46
It's The Month of May, Number 88 in a series. For us in northeast Georgia, it seemed cooler than an average May, and if it was, it was just barely.

Here are the usual temperature anomalies products, at the National Weather Service Climate Prediction Center. Displayed is the mean temperature anomaly. Click on it and you'll get the high and low temperature anomalies on a new page.

The much colder April for the midwest warmed to just a bit cooler than normal in May. The region of unusual warmth in the West expanded at least somewhat into the remaining western half of the US. into the southwestern corner of the country. Much of the eastern US cooled below normal, although not by more than two or three degrees.

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

The dry conditions of most of the year to date continued in the West, although there was spotty improvement, especially in the Pacific Northwest. There was no particularly obvious wet or dry trend over large areas, unless it was for continued wetter than average for the northern and central midwest. The southeast continued with at least normal precipitation, except for the Gulf Coast region, which was much drier than usual.

For the Athens, GA area:

Here is a plot of our daily temperatures excursions in May, along with precipitation amounts as experienced in Wolfskin. In December and January we had higher than normal temperatures; in February we returned to seasonably cold weather. Cold weather intensified in March, with the average temperature much below normal for much of the month. April returned us to average temperatures, and May was just below average. Rainfall was fairly uniform throughout the month, with no huge deluges or long periods of dryness.

The average monthly temperature for May was 67.4 degF, a little over 2 degF below average. We had 0 day more than 1 standard deviation above normal highs (4.5 normal). There were 7 nights with temperatures more than 1 standard deviation below normal lows (5.5 normal), and by this imbalance we had a colder than normal May. We broke no records, although we matched the record low of 1979 on May 25.

The monthly histogram below shows the breakdown of high and low temperature range counts from May 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 breakdown for daytime highs showed a significantly greater number of cold days (in the 60s, F) than normal, but all the other ranges are inside the error bars. For nighttime lows, there really were no ranges that achieved significance. By this criterion it would be hard to say that we were particularly colder than normal.

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.

We had the welcome blue of surplus rain, greater than one standard deviation, for most of the month, and ended up above average in the end.

Our total out here was 3.80", and the official recording in Athens (shown here) was 3.63". 3.00" is normal for May (yes, the new 30-year average for May is much lower than in past 30-year windows).

We have, in fact, stayed just above average rainfall all year since mid-February.

It's about time to take another look at our occasional figure for cumulative rainfall. The most important line here is the blue one: the deficit in rainfall since January 2005. Even with our just above average rainfall this year, the bitter truth in the long term is that we're still more than 20 inches below normal. This is an ongoing trend that began in 2006 or 2007, and was broken only in 2010, resuming a downward path in 2011 and 2012.

Prognosticator stuff:

What is the neat prognosticator telling us? A month ago, it told us the truth: in terms of both precipitation and temperatures - May was to have been cooler and wetter, grading to normal for us in northeast Georgia. As of May 28, the next month will be relatively normal in temperature and rainfall. I'm sorry to tell you that for most of the US, temperatures will be above normal over the next three months, especially for the west TX, NM, CO region. For us, at least, rainfall will be normal over the JJA summer period.

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 Jun 3, ENSO neutral conditions continue, and are expected to remain neutral throughout the Northern Hemisphere summer. We've remained ENSO neutral now for over a year. The last such lengthy period was 10 years ago, 2003-2004.

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

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