Lawrenceville Weather Blog

Georgia Drought Loosens its Grip as Snow Falls in Las Vegas

2008-12-18T14:40:04Z

Last week’s rainfall greatly reduced the intensity of the drought in Georgia, according to the latest update to the drought monitor, shown at right. Before last week’s rain, exceptional drought was the rule north and east of Gwinnett County, some 11% of the state. This week, no part of Georgia is in exceptional drought, and almost 70% of the state is drought free.

Only a small area of the state between Savannah and Brunswick increased in its rain deficit, going from normal to exceptionally dry. The newest outlook through March, 2009 calls for continued improvement for drought conditions in the southeast, and for drought to develop in the Florida peninsula and extend in Texas.

The updated drought outlook doesn’t square well with the latest long range outlooks from the Climate Prediction Center, released this morning. The temperature outlook for January is for warmer than normal east of the Rocky Mountains, except for South Georgia and Florida, which could be colder or warmer than normal. Below normal precipitation will occur south and east of a line from southern Louisiana to eastern North Carolina, more or less south of I-85.

For the first three months of the new year, warmer than normal temperatures are predicted east and south of a line from New Mexico to Wisconsin. Colder than normal temps are in line for the Pacific Northwest, with the Northeast possibly going either way. The three month rainfall outlook calls for above normal precipitation in the Ohio Valley, and below normal rain in the southeast.

Snow in Las Vegas

This has certainly been a month where snow has turned up in places you wouldn’t expect it to, and in record amounts. In addition to snow in Houston and New Orleans earlier this month, yesterday brought record snow to Las Vegas, Nevada. “Las Vegas Hits the Jackpot,” trumpeted the Weather Service’s record event report for Wednesday. The Las Vegas Weather Service office reported 3.6 inches of snow, the most ever in December, and the 8th worst snowstorm since recordkeeping began in 1937. Up to 7 inches of snow was measured in suburban Henderson, Nevada. In California, 5 inches of snow was measured in Boulevard, which is in interior San Diego County, and up to 20 inches of snow fell in the mountains to the east of Los Angeles. A light dusting was even reported in Malibu.

While Atlanta basks in what could be near-record temperatures today and Friday, the snow will continue to move north and east, setting the stage for a possible white Christmas, but not here.

How Much Rain is Needed to Fill Lake Lanier?

2008-12-18T02:13:54Z

The rain last week raised the water level of Lake Lanier about a foot, which likely means that Atlanta’s water supply won’t reach a record low in 2008. As usual, the mainstream media issued stories which said that the rain is good, but the drought isn’t over yet, we’ve got a long way to go, etc. &ct.

Now comes the Southeast River Forecast Center with the best estimate (PDF) I’ve seen for what it will take to get Lake Lanier to full pool — or 1071 feet above sea level, about 20 feet higher than where it is today.

Surprisingly, it’s only 10% above normal rainfall for a year.

The forecast center measured annual precipitation against Lake Lanier’s level since the lake began to fill back in 1952. It determined that, on average, 60 inches of rain fell in the lake’s drainage basin per year, providing about 1.36 million acre feet of water. Using those figures, and accounting for the fact that the Corps of Engineers has restricted the outflow from Lanier over the past year, the Forecast Center says,

Lake Lanier’s pool was at 1054 feet msl at the beginning of this water year (1.37 million acre-ft). To get to full pool at elevation 1071 feet msl, an additional 585,000 acre-ft of inflow is needed. However, this assumes no outflow. If we apply the annual average outflow of last year for this year (1070 cfs), 775,000 acre-ft are released downstream. So the total inflow volume needed to fill the reservoir and sustain a release similar to last year is 1.36 million acre-ft.
…[T]his would put the total annual precipitation at around 65 inches (following the lower end of the trend). This is only about 10% above normal.

Of course, part of the equation depends on when the water comes. If we get a lot of excessive rain in the winter, it will count more than if we get it in the summer, since the heat and absorption by plants prior to the water reaching the lake will be higher in the summer months. The calculations used in the analysis are based on rain during the water year, which starts on October 1, and there has already been six inches of rainfall. That means there are only 59 inches to go.

I listened to Lieutenant Governor Casey Cagle (who is clearly running to become governor in 2010) addressing the Gwinnett Chamber’s monthly meeting this afternoon. He dumped most of the problems with metro Atlanta’s water supply on the Corps of Engineers favoring mussels in Apalachicola Bay over the water needs of Georgia. He also offered an innovative idea for increasing the water available to metro Atlanta. He estimated 10% of the lake’s capacity had been lost due to silt (something I’m not going to argue with). By dredging the lake, Cagle says we could not only expand the lake’s capacity to hold more water, we could recycle and resell any valuable materials that were dredged up.

In my mind, Cagle’s plan will only work if Georgia gets some formal rights to the lake’s water. Based on court decisons and the official use plan for the lake, we aren’t there yet.

November 2008 Weather In Review

2008-12-16T00:58:08Z

Temperatures across the Southeast remained colder than normal in November, and Georgia recorded its 27th wettest November out of 114, unfortunately with most of the rain in the southern part of the state. For the entire United States, it was the 10th warmest and 41st driest November since recordkeeping began back in 1895, according to the National Climate Data Center.

Most of the above normal temperatures were in the west, with nine states from Colorado to California having top 10 warm Novembers, and five states having top 5 warm Novembers. Because of the trough that sat over the eastern half of the country for most of the month, most of the states east of the Mississippi were colder than normal, with Georgia and South Carolina experiencing top 10 (or should that be bottom 10) coldest Novembers.

Only North Dakota had a top ten wettest November, with most of the country having about normal rainfall. However, the Midwest and South had their 27th and 28th driest November on record.

Of course, the cold November weather in the Southeast doesn’t compare to what’s going on now in the plains states. This morning’s low was 33 degrees below zero in Havre, Montana, the coldest spot in the country. The western trough is bringing Siberian air to much of the country, as you can see by looking at the US temperatures early this evening;

A strong cold front is running along the Mississippi and Ohio rivers, with locations to the east much warmer than those to the west. Yesterday, Denver recorded a new record low for the date of 18 below zero. The previous low record was -14, set in 1901. Fortunately for those of us in the Atlanta area, the front isn’t going to get this far, and we should see warmer than normal temperatures through the end of the week.

Above Normal Hurricane Season Predicted for 2009

2008-12-13T00:35:39Z

Earlier this week, the Dr. Gray and his team at Colorado State University issued their initial outlook for the 2009 hurricane season. The early outlook predicts a continuation of the above-normal tropical activity we’ve seen over the past few years. The outlook is for 14 storms, compared to over nine in a normal year, and seven hurricanes, compared to six in a normal year. There should be three major hurricanes, and there’s a 63% chance of a major hurricane making landfall somewhere in the United States–about 20% greater than in a normal year.

Last year at this time, CSU predicted there would be 13 named storms, seven hurricanes and three major hurricanes. The result ended up being 16 storms, eight hurricanes and five major hurricanes, so they underestimated. However, their new model for predicting hurricanes from this far out is apparently more accurate than the model they used previously.

A few other weather tidbits:

if tonight’s full moon seems brighter than usual, it’s because the moon is closer to the earth than it’s been for the past few years, and the first time in 15 years that the close approach, caused by the Moon’s elliptical orbit, has occurred during a full moon. Coincidentally, the moon is riding higher in the sky than any other full moon this year. The sun and moon follow opposite visual paths–when the sun is low close to the winter solstice, the moon is high in the sky, while in the summer, when the sun is overhead, the moon is low in the sky.

Another astronomical factoid — today is the first day that the sun begins to set later in the evening than it has since back on July 5th. Day will continue to shorten for another ten days, due to the sun rising later. We won’t get an earlier sunrise until January 13th.

The storm that brought welcome rain to much of the southeast is now history, having moved up the east coast and causing major power outages in the northeast. Much of Massachusetts was caught in an ice storm, with considerable damage. Albany, New York had .6 inches of ice, while Schenectady reported .88 inches of accumulated ice.

We are about to see a big pattern change in the weather across the United States. The past month or so has been dominated by an upper level trough in the east and a ridge in the west. This pattern brought warmer than normal conditions to the west, and colder than normal weather to the east, as the jet stream dived south, following the path of the trough.

Now, a trough is developing in the west, which will bring colder than normal weather there, but more seasonable, if not warmer than normal weather to the Southeast. There’s a better than normal chance of above normal temperatures for most of the south through Christmas, and it looks like we’ll get some additional rainfall, too. Lake Lanier’s current level is 1051.88 feet–more than ten inches above where it was on Wednesday before it started to rain. The AJC reports that yesterday was the first day since the record low level last December that the lake level in 2008 was higher than it was on the same day in 2007.

Powerful Southeast Storm Brings Snow to Houston, New Orleans

2008-12-11T19:09:51Z

A powerful low pressure system is making its way across the Southeast US today, bringing rain and flooding to parts of Georgia and Alabama, and rare snow to Houston and New Orleans. Here’s a satellite picture of the storm taken about 11:15 this morning:

It’s the first time there’s been snow in Houston or New Orleans since Christmas Eve, 2004. About an inch of snow fell in New Orleans, although three inches fell in Baton Rough and five inches was reported north of Lake Pontchartrain. Parts of Mississippi reported between two and four inches of snowfall.

Metro Atlanta received more rain this morning, mostly on the order of 2/3 of an inch. However there is still a chance for additional precipitation as the upper low moves just north of Atlanta later today.

More Rain in the Forecast With a Slight Chance of Snow

2008-12-11T01:01:46Z

North Georgia got plenty of rain today, and it looks like there’s more to come. As of 7:30 Wednesday, I’ve recorded 1.79 inches of rainfall, the most since October 8th, when another massive low pressure system rolled through Georgia and brought 2.31 inches of rainfall.

Other areas in the Peach state got even more. Since 7 PM yesterday:

Alpharetta - 1.84 inches
Atlanta - 1.76 inches
Athens - 0.76 inches
Cartersville - 1.65 inches
Chamblee: 1.91 inches
Dunwoody: 2.07 inches
Gainesville: 1.5 inches
Macon - 2.25 inches (and record precipitation for December 10th)
Peachtree City - 2.2 inches
Rome - 1.65 inches

In addition to the rain, there was a tornado sighting today near Tallapoosa. The weather service reported an F0 tornado early this morning 3 miles northeast of that location in Haralson County. Closer to Atlanta, flooding is forecast for the Big Creek in Alpharetta.

All the rain has been good news for Lake Lanier. The latest reading has the lake level at 1051.17 inches, which is .18 of a foot, or about 2.2 inches higher than it was early this morning. And, the rain is not over yet. Overnight a second wave of wet weather will visit north Georgia, possibly doubling the amount of rain we’ve had already.

By tomorrow night, the upper low that has been responsible for much of the rain will move northeast of Atlanta, and the cold front associated with it will bring a chance of snow to the northwest part of the state. Because of the warmup due to the rain, it’s not expected to produce any accumulation and if there is any, it should be confined to the northwest corner of Georgia. Folks in Mississippi aren’t so lucky, though. The weather service has issued a winter storm warning for much of eastern Mississippi, predicting 3-5 inches of snow. In Louisiana, half an inch is possible.

There Could Be a Lot of Rain Next Week Before It Turns Warmer

2008-12-06T23:44:51Z

I’ve been keeping an eye on a potential weather situation coming up next week that could bring a lot of welcome rain to North Georgia. Since the beginning of the week, the Climate Prediction Center has indicated the potential for heavy rain for much of the Southeast for Tuesday-Thursday. The latest drought outlook, issued last Thursday, called for drought relief in the southeast, a marked change from the outlook two weeks ago. Now, this potential is beginning to show up in the precipitation forecasts for Tuesday night through Thursday night, as you can see to the right.

If the outlook is correct, (and remember this is four or five days away), Metro Atlanta could have as much as 3.7 inches of rain — enough perhaps to prevent Lake Lanier from dropping lower than it did in December last year before the winter rains kicked in.

The real question is the exact path of the upper low that ultimately is going to bring the rain our way. The models have been bringing it further and further eas, which would increase the amount of rain in the Peach State. Indeed this morning’s forecast had the bulk of the rain slightly further north and west, putting Atlanta and Northeast Georgia in another “we just missed the heavy rain” situation we’ve seen so frequently.

No matter how much rain we get with this storm, it marks the start of a pattern change that sets up a trough in the west. The effect of this is that the colder air that brought us much colder than normal temperatures for the past few weeks is going to move to the west, and we will see at least a temporary warmup beginning next weekend that could push daily highs into the 60s and lows in the 40s beginning on the 15th.

New Outlook for December: Cold in the East

2008-12-02T00:14:51Z

Over the weekend, the Climate Prediction Center released its revised December temperature outlook, which looks quite a bit different than the one they released back on November 20th. The old version had warmer than normal conditions predicted for an area centered on Oklahoma and Kansas, while the new one, as you can see below, says it’s going to be warm in the west and cold in the east:

The other possible bit of good news for rain-starved Georgia is that the precipitation outlook has changed as well, with what was a 33% chance of drier than normal weather in the state changing to equal chances of above or below normal rainfall.

The updated temperature outlook brings the Weather Service more in line with what other winter forecasts are saying, and with what the CPC’s 6-10 and 8-14 day outlooks call for, which is for a significant chance of below normal temperatures for most of the US and above normal precipitation for all but the desert southwest from the 7th through the 15th of December.

November certainly provided a good lead in to the cold weather, at least here in Georgia. At Atlanta’s Hartsfield Airport, the average temperature for the month was 50.5 degrees, 2.8 degrees below normal. It was a little cooler out here in the ‘burbs, with my thermometer recording an average temperature of 47.9 degrees. Despite around an inch and a half of rain throughout most of the Atlanta metro area from Friday through Sunday, we ended up with 2.64 inches of rain at Hartsfield, or 64% of normal. Here, I got even less, with 2.7 inches of rain, 1.5 of which we got over the weekend.

November 30th also marked the end of the 2008 hurricane season. It was an above average year, with 16 named storms, eight hurricanes, and five intense hurricanes. Hurricane Ike became the third most expensive hurricane to hit the US, after Katrina and Andrew. Tropical Storm Fay set a record, striking Florida four separate times back in August.

Not Much Rain Today, But More to Come

2008-11-25T00:46:01Z

While I suppose that North Georgia should be grateful for any rainfall it receives, today’s rain did very little to reduce the deficit we’ve had in November, much less for the year. Locations in Atlanta, Gainesville, and North Fulton counties all reported less than 1/3 of an inch of precipitation… here in Lawrenceville, I recorded .22 inches. While there’s a chance of more rainfall overnight, it looks from the radar that the following cold front is moving in, and the rain is moving out.

So as of now, I’ve recorded .67 inches of rain in November, a month that typically has slightly over four inches of precipitation. That’s 20% of normal. so far. There’s a good chance that we’ll have more before the month ends.

After a blustery day on Tuesday, conditions improve for Wednesday and Thanksgiving. By early Friday morning, though, another round of rain is headed our way. The moisture for Friday’s rain will come both from the Gulf an the Pacific, and we could see over an inch between 1 AM and when the rain moves out after sunset. (Sorry shoppers, but you’re likely to get wet on Black Friday).

If you believe the latest GFS forecast models, more rain will be on the way Sunday to end the month, and December will start with some rain on Wednesday the third. Both those storms are predicted to bring over an inch of rain to the area. The models have been known to be wrong before, but we can hope for the best.

It looks like the colder than normal temperatures will be continuing as well, at least for the next two weeks or so. The CPC long range outlooks call for below normal temperatures to continue for most of the US through December 8th. Atlanta’s November temperatures are running 3.3 degrees below normal for November, and December should be below normal as well.

With colder than normal temperatures and higher than normal precipitation in the forecast, does this mean that Atlanta has a chance for some rare December snow? Typically, when it’s cold, we have dry weather, while when there’s precipitation, it warms up. There’s no snow in the forecast yet, and the odds of a white Christmas are statistically very low.

Weather Services Releases Winter 2008-09 Forecast

2008-11-22T00:45:02Z

Our friends at the Climate Prediction Center have finally released their 2008/2009 winter outlook, which calls for warmer then normal temperatures for much of the Mississippi Valley states, and drier than normal weather for most of the southeast and Gulf Coast. Here’s the temperature outlook:

And here’s the outlook for precipitation:

The CPC admits that without strong signals for either an El Nino or a La Nina winter, it presents a challenge to create its outlook, and admit that there could be a lot of variability in the weather this winter:

“These patterns are only predictable a week or two in advance and could persist for weeks at a time,” said Michael Halpert, deputy director, Climate Prediction Center. “Therefore, we expect variability, or substantial changes in temperature and precipitation across much of the country.”

if the outlook holds true, Georgia will experience a warmer than normal winter in the northwest part of the state, extending through the Atlanta metro, with less than normal precipitation, especially in the southern part of the state. The winter outlook is based on the CPC’s normal 3 month outlook for December, January and February which was released on Thursday, and pretty much follows the ideas they have had for the past few months.

I don’t know how much faith I have in their outlook, though. So far in November, Atlanta is running about 2.6 degrees cooler than normal, and I don’t see that trend changing through December. (The rainfall deficit seems to match the weather service’s ideas, though.) So if December is cooler than normal, we’re going to need a warm January and February to make up for it.

Updated winter forecasts from Accuweather and others will be available soon, and I’ll keep you posted.