Rainfall Still Lagging, but Drought Improving
I got a comment from Matt asking how we’re doing with the drought, given the recent rainfall, and rather than answering his question in another comment, I decided to do a new post.
In reality, with 9.79 inches of Atlanta is still behind what would be ‘normal’ rainfall by 2.44 inches as of yesterday, and some of that deficit has been reduced by today’s storms. However, we are doing better than as of this time last year. In 2007, Atlanta had recorded only 7.71 inches by March 14th, 2.08 inches less than in 2008. In Gainesville, which has had 10.74 inches of rain so far, they are ahead by 2.17 inches. Here in Lawrenceville, I’m only showing .86 inches more rain than this time last year, but keep in mind I don’t have an ‘official’ rain gauge.
Even though actual rainfall varies across the metro area, it’s probably safe to say that we’re two inches ahead of where we were this time last year. Plus, in 2007, the second half of March ended up being rain-free, so by the end of this month, we are likely to be even further ahead of 2007.
Most of this year’s rainfall shortfall came in January. December, February and March to date precipitation amounts are about normal. In my mind, this is good news from the drought perspective. The latest drought monitor shows only 43% of the state in a drought, compared to 87% in mid December, and only 4.3% in exceptional drought conditions, compared to 49.9% three months ago.
If you take a look at some of the long range outlooks, once we get past April and May, we may be returning to normal or above normal precipitation. CPC models indicate above normal rainfall for June, July and August. Part of the reasoning for this is that the La Nina conditions would diminish as we get into the summer months, but in my opinion, we haven’t seen what was predicted due to La Nina, except maybe in January. Part of the outlook may also be due to an expected boost in rainfall due to the approaching hurricane season.
To sum up, I think we’ve dodged the bullet of an extremely dry winter, and things look optimistic for a return to more normal rainfall this summer. The effects of the drought linger, though, evidenced by the water level on Lake Lanier, which hasn’t risen as much as it normally would during the winter. It took a few years for the drought to develop, and it will take a while to get out of it as well.
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March 16th, 2008 at 7:33 am
[...] in all, we’re still running a little below the normal pace for the year, but we’re doing a bit better than this time last year. However, Lanier is still much lower [...]
March 18th, 2008 at 9:15 pm
Thanks for the reply/post. Good information and puts things into somewhat more perspective.
The CPC link to the maps jive pretty much with the CPC long term precipitation maps that I refer to often. What’s the most accurate representation, in your opinion of the CPC maps?
I notice now that Lanier is up to levels last seen in early November 2007. I think you’re right - we dodged a bullet.
Talking to a coworker the other day, about la Nina, Lake Lanier Levels, long term forecasts, and the like, and got an idea — has anyone ever correlated Lake Lanier levels with la Nina sea temperature observations? Seems like, if la Nina caused the drought, then there would be some correlation. Or, probably a better comparison might be rainfall. But rainfall might be skewed by tropical storms and hurricanes in the summer. Ever thought of doing something like that?
March 19th, 2008 at 6:22 pm
The CPC model maps provide a lot of the input into the long range official CPC outlook maps. One advantage of the model maps is that they are updated/initialized daily, so they might be more current than the official long range outlooks, which are updated on the third Thursday of the month.
While human forecasters might be able to better predict the weather over a short period of time, I think that benefit diminishes the longer you look into the future. Of course, models are going to have their biases which are going to be more magnified the longer you go out - look at some of the global warming models to see examples.
I’m not so sure how useful it would be to correlate Lake Lanier levels with La Nina, primarily because the La Nina didn’t by itself cause the drought. The La Nina started in the fall of 2007, and perhaps prolonged its effects. Last year, we were in a El Nino, which in theory should bring more than usual rain, but where did that get us?
Climatologists pretty much know the typical effects of changes in SSTs on weather patterns in the United States, and there’s lots of informatoin available on this. I don’t know if someone has ever done a true statistical correlation coefficient on the relastionship between SSTs and weather patterns, though.