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

Sunday: 6 October 2013

The Month of September  -  @ 07:01:08
It's The Month of September, Number 92 in a series. Both temperatures (warmer) and precipitation (much drier) took a big turn for us here in northeast Georgia in September.

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

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

Most of the US was warmer, like us, to much warmer, in the central states. Southern CA and western AZ were much cooler than normal (again), while the northwest continued much warmer. The northeast continued cooler than normal, but warmer than normal temperatures invaded most of the eastern US for the first time in a couple of months.

Again, the high and low anomalies graphic (click on above figure) shows that nights were warmer than days were cool. And again this effect was particularly pronounced for the West, by whatever means.

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

For most of the western US, September brought copious amounts of rain, while central CA remained dry for at least the second month. Other than east TX, LA, and MS, the rest of the country east of center remained normal, or drier than normal, especially the midwest.

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.

As in August, the daily highs seldom went above 90, though this is not unusual in September. The rainfall that began in June and continued through August finally came to an end for us. We only had two precipitation events resulting in a total of 2.17", while 3.94" is normal. Athens claimed 2.42".

We did not break any records in September. The average monthly temperature for September was 73.2 degF, just 1.7 deg lower than the 30-year average of 74.9. Cooler, yes, but not nearly as cool as August's 5 degF departure.

We ended up with 0 days more than 1 standard deviation above normal highs, and 1 night with temperatures more than 1 standard deviation below normal lows.

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

This time the histogram reflects fairly well the average temperatures for September. There was virtually no difference between last month and the average September in the number of days experiencing any particular range.

Last but not least, 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 finally have a plot that shows a rainfall deficit. Official Athens rainfall was at 2.42", just 60% of normal. It never really seemed dry, though, with so much rain the previous three months. I think it took that 4 weeks with no rain (Aug 22-Sep 20) just to dry out completely.

At nearly 51" right now, we're 3" above normal rainfall for the year, with three months remaining.

Prognosticator stuff:

What is the neat prognosticator telling us? For us here in the southeast, it has been accurate over the last three months for temperature and precipitation. As of 5 October, it tells us in the Southeast that we can expect several weeks of much warmer temperatures. As I look at the forecast for the next ten days it looks like tomorrow will drop 10 degF for the foreseeable future, so I'm not so sure about the prognosticator there. Thereafter we'll have an equal chance of normal temperatures through December. The picture is quite different elsewhere, so be sure to take a look if you're not close by us.

Precipitation will be highly variable across the US, but at least in Athens the three month outlook will be for equal chances of rainfall after we get through this dry spell in the nest week or so.

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 30, ENSO neutral conditions continue, and are expected to remain neutral throughout the Northern Hemisphere winter. We've remained ENSO neutral now for 16 months. The last time we had such a lengthy period without an El Niño or La Niña was 2005-2006.

NOAA's Monthly State of the Climate product for August is available, or will be when the government shutdown is over. And last year's annual report for 2012 regionally, nationally, and globally is also available.

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