By Doug Schneider

The remains of Hurricane Michael have cleared out of Georgia, and it has been a beautiful day at Road Atlanta, although it has been quite windy, with gusts around 30 mph. The Gainsville airport, which is located about 10 miles north of the track, recorded 2.68 inches of rain from Michael.

A cold front has moved through the area, and winds have shifted to the northwest as high pressure builds into the area. This high will continue to dominate the weather pattern over the Southeast through Saturday, which will provide really nice weather for racing Friday and Saturday. Temperatures will be comfortable in the afternoon, reaching the lower to mid 70s, and morning lows will be cool, in the lower 50s. Humidity levels will be very pleasant too. Winds will be lighter tomorrow around 10 mph), and even lighter on Saturday (5-10 mph). 

Since I'll be at the track Friday and Saturday, and since the weather looks quiet, I don't plan to have another post here to update the forecast. I will have some posts on our Twitter and Facebook accounts, which you can find on the right. See you at the track!  

By: Stephen McCoy

Cool conditions remain in the forecast for the Six Hours of Fuji, however the higher chances of precipitation have shifted more to Friday and Saturday night into Sunday morning.

The pattern in the upper levels looks to stay relatively consistent with the previous forecast with a longwave trough moving through on Friday with a shortwave trough following close behind, and conditions returning to a more zonal flow on Sunday. At the surface, the cold front from a low pressure system to the north is expected to linger in the area on Friday, with a chance for rain concentrated in the morning and possibly early afternoon. Due to high pressure to the east, winds will be from the east to northeast, though with a slightly stronger pressure gradient winds will be around 5-10 mph (8-16 kph).

An area of low pressure is expected to form to the south of Japan, ahead of the shortwave trough, and could bring a slight chance of showers to the region Saturday afternoon or evening. The system is expected to track to the northwest, approaching the southern coast overnight Saturday into Sunday morning before turning east towards the North Pacific Ocean. There is a likely chance of rain during this time frame, with chances decreasing as the day progresses. Winds will continue from the northeast as winds wrap cyclonically around the low.

High amounts of relative humidity in the low levels will keep conditions mostly cloudy to overcast for most of the forecast period. A shift in low level winds to the north on Sunday afternoon is expected to erode some of the cloud cover into the evening hours.

By Doug Schneider

​Click images to enlarge

The forecast for Hurricane Michael has stayed pretty much the same over the past couple days, and so my forecast for Petit Le Mans hasn't changed much either since Sunday.

Scattered light showers have been around northern Georgia today, and that will continue tonight, with showers becoming a little more numerous and heavier Wednesday morning. On/off showers are expected through the day, not directly associated with Michael. These showers should be fairly light, so I've changed the Impact Scale on Wednesday to low. I think the planned testing sessions that day should be able to be run without weather interruptions, although the track will likely be wet at times.

Michael will start to impact the track on Wednesday night. Here's a bullet list of impacts that can be expected from Michael at Road Atlanta:

• Timing - Outer rain bands from Michael will spread into Road Atlanta Wednesday evening, probably around sunset, give or take a few hours. The heaviest rain will fall at the track from after midnight until around noon on Thursday. Rain will be decreasing in intensity and frequency on Thursday afternoon.
• Rain amounts - From Wednesday through Thursday, around 1.5 inches is expected give or take a few tenths, with 2 inches being possible on the high end and around 1 inch possible on the low end. This will likely not be enough rain to cause flooding problems, but there is a creek near the support paddock and the eastern side of the track that will bear watching if amounts are higher than expected.
• Wind - Not expecting wind to be a big problem, but it will be breezy on Wednesday night and Thursday, with sustained winds of 10 to 20 mph and gusts as high as 30 mph at times. This could be an issue for those who are setting up tents or canopies.

A cold front will move through Thursday evening, which will merge with Michael and bring cooler and drier air behind it. A large high pressure system from central Canada will be building southeast, and the weather for Friday and Saturday will be absolutely gorgeous, with a northerly wind bringing highs in the mid 70s and morning lows in the mid 50s.  

By: Stephen McCoy

A cool and wet weekend looks in store for the Six Hours of Fuji this weekend with temperatures hovering around 60 degrees Fahrenheit (15.5 degrees Celsius) each day.

An upper level longwave trough currently centered over eastern Mongolia and northeastern China will persist over the region in the coming week. Towards the end of the week, the trough will deepen slightly, extending southwestward as the trough itself moves east. Much of Japan will be downstream of the center of the trough, resulting in upper level winds being primarily from the southwest for the first part of the weekend. With winds from the southwest, moisture will move into the area in the upper levels from the East China Sea and the Philippine Sea. As the longwave trough moves past Japan on Friday, a shortwave trough is expected to develop behind the longwave trough and to the west of Japan. This shortwave trough will pass over early Sunday morning, where conditions will return to more zonal flow with upper level winds from the west.

The aforementioned longwave trough will cause a surface low pressure system to develop over the Korean peninsula and the Sea of Japan around mid-week. As the trough moves eastward, the surface low is expected to move northeast towards the Sea of Okhotsk and eventually the North Pacific Ocean and an area of high pressure is expected to build in. With the high to the west of Japan and the low to the northeast, the area where the two systems meet will cause winds to propagate from the north to northwest, bringing cooler temperatures from northeast China and parts of Siberia. As the surface high continues to build in towards Japan, the winds are expected to shift more to the northeast during the day on Friday. These winds will bring moisture from the Sea of Japan to the region, resulting in a high chance for precipitation during the day.

On Saturday, a surface low pressure system could develop to the south of Japan ahead of the shortwave trough before moving eastward out to the Pacific Ocean. Depending on the location in relation to the southern coast, the system could bring more precipitation to the region as moisture would wrap around the low from the south and east. Should the low pressure system, winds would increase slightly, though they would continue from the northeast due to the area between the two systems being located over the region.

On Sunday, the return to zonal flow will result in upper level winds bringing drier air from the mainland. Moist air in the lower levels will cause some mostly cloudy to overcast skies throughout the day, but with drier air aloft, the chance of precipitation is minimal. With winds continuing from the north to northeast, temperatures will remain cool through the day.

By Doug Schneider

'The big story for the weather during Petit Le Mans will be the effects of what is currently Tropical Storm Michael. Michael is currently located just off the Yucatan Penninsula, and is forecast to track north over the next few days. It is expected to make landfall as a Category 1 hurricane along the Florida Panhandle. From there, it is forecast to curve northeast across Georgia and the Carolinas.

So what will be impacts be for Road Atlanta? First, don't focus on the exact track of Michael. The track isn't going make a huge difference in the impacts, because tropical moisture will be spreading across Georgia ahead of it, producing a lot of rain. The intensity rating of Michael won't matter much either, as heavy rain will be the main impact at the track, with wind being a lesser impact. The amount of rain that will fall remains uncertain, but here's what the forecast for the NWS' Weather Prediction Center shows:

That graphic shows 2 to 4 inches of rain at Road Atlanta in northeast Georgia from Wednesday morning through Thursday night. That is certainly possible, but a big factor in the amount of rain at the track will be the speed of Michael. The good news is that the system is expected to keep moving across Georgia and not stall out, as it will get picked up by an upper level trough and cold front approaching from the west. A faster movement will result in less rain. 

The rain from Michael will be around the track from Wednesday through Thursday, but right now it appears that the heaviest rainfall will be Wednesday night, with decreasing rain amounts through Thursday as the system pulls away and a cold front moves through. 

Behind that cold front, high pressure will be building into the Southeast, and the weather looks great for Friday and Saturday. With the departing low of the remnants of Michael and the building high pressure, Friday will be a little breezy. Temperatures and humidity levels will be quite comfortable, with highs in the lower to mid 70s both days, and lows in the 50s.