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

Tuesday: 5 August 2014

The Month of July  -  @ 16:00:25
It's The Month of July, Number 102 in a series. For us, July was mostly even in overall temperatures, although somewhat below normal, and for us very locally, much drier than usual.

And along about July 16 we began to slide back into winter, on average. That sounds great right now!


Here are the usual temperature anomalies products, at the National Weather Service Climate Prediction Center. Displayed are the mean temperature anomalies, not the absolute temperatures.

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

Warm anomalies expanded substantially in the West in July, while the eastern 2/3 of the US was quite a bit cooler than average, especially in the Central US. If you didn't hear about the summer polar vortex, then you almost certainly missed the better meteorologists deploring the use of the term.

The National Weather Service Climate Prediction Center's precipitation plots are no longer being updated here. Last month's alternative is also not being updated here. *Now* the closest I can find to the old familiar anomaly map is accessible from here. It's still much less flexible but at least looks a little more like a precipitation map should.

While dry weather continued in the West, there was some relief in the Pacific Northwest and along the Nevada California border. Rainfall remained below normal levels along much of the California coast and inland for half the state, though. It's always good to keep in mind that when we talk about normal rainfall here in Georgia, it's in the range of 4" per month - when in the western states, 0.4" per month might be bountiful.

Not only was a good bit of the eastern 2/3 of the US cooler than normal, it was also drier. The Great Plains, Great Lakes, and northern tier of states were quite dry in most places. The southeast was spotty, but a good bit got less than half the usual rainfall. (Contrast that with last July, when we got over 9", and NOT due to tropical storms, either.)

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 30-year average daily temperature, which halfway through is beginning to move back downwards as expected.

As was true in June, temperatures were fairly monotonous through most of the month. We did have a few warm periods, but nothing particularly hot, and around the 19th a very significant cooler period of five days with over an inch of rain. Toward the end of the month, just a few days ago, we had another cool period of three or four days.

Here in the Athens area, we were somewhat below normal for the average temperature in July. The Athens area mean temperature during July was 1.3 degF below the average 80.7F. Athens matched a record low from 1925 on July 30, 60F, while out here we actually went below that by one degree.

We had 2 days more than 1 standard deviation above normal highs (considerably below the average of 5.2 such days). We had 9 nights with temperatures more than 1 standard deviation below normal lows, well above the average of 4.5 nights.

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

Except for one slot in the ranges, none of our individual brackets were significantly different from the average. That one was 2 nights at 60F or below, but this is hardly compelling. While I like the histograms, they have their place in adding to rather than replacing simple averages.

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.

Athens had a significant period of precipitation in July, while out here in we didn't have half that. So Athens had 4.22" of rain, and we had 1.93", less than half the monthly average of 4.47". We're still a bit below average for the year, about like 2009, 2010, and 2011 at this point.

Here's the monthly totals for our CoCoRaHS stations in Oglethorpe County. I'm presenting this just because the nearly two-fold variation is so great (mine is the lowest one). Usually over the course of the month the expected variable thundershowers will even out over a region as large as our county. Not this time!

Prognosticator stuff:

What is the prognosticator telling us (as of August 5)?

Unfortunately temperatures are going to remain hot in the West, although less extreme western points may cool off during the next three months. Amazingly precipitation seems to have about a 50% chance of normal levels over the region, for that time period.

Very roughly, for the next 6-10 days the chances of higher than normal temperatures are going to prevail for the north, and for both the east and west portions of the country. For the following 2-3 months, this pattern of higher than normal temperature chances will continue for the Southeast and the West.

In the east and southeast, we're scheduled for more rain over the next couple of weeks, along with cooler temperatures. But the pattern excludes the southern portions of the Gulf states and Florida. By one month, we're back to normal, and then warmer than usual temperatures in October.

One caveat I've noted with this prognostication - it seems to use historical trends, as well as an ENSO expectation, to predict. That may well be the reason for normal rainfall in California, as well as in our area, so if an El Niño doesn't develop, or isn't as strong, those predictions may fail.

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 August 4, ENSO neutral conditions continue, but with above average sea surface temperatures in the equatorial Pacific. The chances of an El Niño developing continue as in July at 70% by the end of summer, and 80% by the fall and winter. The planet has remained ENSO neutral now for 26 months. The last time we had such a lengthy period without an El Niño or La Niña must at this point have been in the 1990s.

Earlier there were thoughts that this might have been an unusual strong El Niño, but developments have been sluggish. One thought is that the very warm sea surface temperatures in the North Atlantic may have kept the trade winds going, rather than slowing or reversing as they do during a strong El Niño. At any rate, the warming central Pacific has not apparently communicated itself to the atmosphere yet, and that's a big part of the global weather changes.

NOAA's Monthly State of the Climate product for June is available.

Summarizing from what I see on the map: California's year up through June is almost 5 degF above normal, and more than 1 degree above the previous record. More than a third of the state is in exceptional drought. Temperatures have been cool in the southeast. Minnesota and surroundings had large amounts of rain in June.

Here is the final annual State of the Climate report for 2013 regionally, nationally, and globally. It's pretty US-centric, but there are comments for climate globally too.

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