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.

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Wednesday night’s threatened winter storm didn’t end up causing too much difficulty for the metro Atlanta area. The onset of snow between 5 and 5:30 PM managed to put about a quarter inch of the white stuff on my yard and caused the temperature to drop below freezing, but by 7:30 PM, temperatures rose above 32 degrees, and stayed constant or warmed up as the overnight hours passed.

Nonetheless, at least some freezing rain was noticed in parts of Gwinnett, even if it was in limited areas. I noticed that ice was still sticking to trees after noon today along Wisteria Drive in Snellville, and the pine trees along Ronald Reagan Parkway were similarly burdened. So much of what happens in a winter storm is temperature dependent, so just a variation of a degree or so can make a big difference.

The continually varying weather we’ve seen this winter has brought relatively normal precipitation to drought-starved North Georgia. December ended up with more than the normal amount of rainfall, and the official rain gauge in Atlanta is close to what we would expect so far in a normal January.

The latest drought outlook, released today and shown at right, calls for improving conditions for much of the northern part of the state including Atlanta, with at least some relief for the rest of the state. We should see another chance of rain and/or snow Friday night and Saturday morning, with more precipitation for the latter part of next week.  Both the 6-10 and 8-14 long range outlooks call a better than average chance of rainfall.

We’re not out of the drought yet.  But, with drier than normal conditions predicted for the winter due to the presence of La Nina, it can’t be a bad thing that precipitation is running close to normal.

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It looks like things could get fairly nasty Wednesday Night and into Thursday for much of the Atlanta area north of Interstate 20, and especially for the northeast counties, including Gwinnett.  An incoming low pressure system in the Gulf of Mexico will bring precipitation to Georgia beginning Wednesday morning.  Meanwhile, the high currently over the eastern part of Kentucky will move northeast, running into the Appalachians, and causing a ‘wedge’, or cold air damming to affect northeast Georgia.

What happens is that the colder air gets trapped on the western edge of the mountains, and the approaching lower pressure, warmer air slides above the colder, heavier air. You can tell when we’re in a CAD situation when the wind comes from the east, and it doesn’t warm up much during the day.

The presence of warm air above cooler closer to the ground tends to favor the formation of sleet or freezing rain, since the warm air layer will melt any snow as it passes through, while the cold air close to the ground will either re-freeze the precipitation, or cause freezing when the water hits the surface.

In the last day, forecasters have increased the total amount of expected precipitation from the storm to almost an inch, while dropping the low temperature Wednesday night, especially in the northeast counties most affected by the wedge.

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While it may not get as bad as the winter storm in North Georgia two years ago, it looks like Thursday morning is going to be pretty nasty.

The Weather Service has issued a winter storm warning for the northern part of the state, including Gwinnett County. They have also issued a winter weather advisory north of a line from LaGrange to Macon to Augusta. The warned area could expect up to half an inch of sleet and a quarter of an inch of ice before Noon Thursday.

Cold temperatures today — the high was only 42 degrees — and dropping temperatures due to the still-clear skies will push the morning low below 30 degrees. Meanwhile the precipitation will arrive starting in the northwest corner of the state, and will most likely arrive in Atlanta after 1 AM, with the worst arriving shortly before sunrise.

The good news is that the precipitation will bring warmer air, with temperatures rising above 32 degrees by noon, and probably staying there through the overnight hours early Friday morning, so the worst should be over Thursday afternoon. Overall, we could get more than an inch of liquid precipitation before things start to dry up late Thursday night.

The longer range outlook keeps things cold in the Atlanta metro area through the middle of February. The Weather Service issued an updated forecast for the month, and while the predictions for the Southeast US didn’t change much, they are calling for colder weather than originally thought in the Northeastern states.

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In a near-repeat of weather conditions from two weeks ago, the possibility of freezing rain has raised its ugly head in North Georgia.

As you may remember from this post, we had a situation two weeks ago with a low pressure system approaching from the south, and cold air in place. This brought the threat of freezing rain or sleet. Although there was a bit of freezing rain overnight, the ground was warm enough, and the precipitation amount was small enough that there weren’t any problems.

The situation this week is different. Unlike two weeks ago, when we set a new high temperature record, it’s been much colder, which increases the chances of any freezing sticking around. Also, instead of 1/10th of an inch of precipitation, we are likely to see about an inch between 7 PM Wednesday and 7 PM Thursday.

Right now, forecasters believe that what does fall could be freezing rain north of a line between LaGrange and Milledgeville. Even after sunrise on Thursday, the line between rain and freezing rain will be just south of Gwinnett County.

Everything is subject to timing of the storm, and the exact temperatures on Wednesday night. We’ll have a much better picture of what is to come on Wednesday morning.

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