You hear us meteorologists talk about it all the time - wind shear. It's one of the key ingredients for tornadoes. But, do you really understand what wind shear is? Most of the time you can't see it. But, fellow pilot Eddie King shared this picture with me while flying over Palm Beach County, Florida. The smoke tells a good story.
Notice how the wind at the surface is moving the smoke in one direction while the wind in the higher altitudes is blowing the smoke in another direction. This is an illustration of directional wind shear. The changing direction of winds with altitude. It's also an example of speed shear. Notice how the smoke is elongated. This means the winds are blowing faster at the higher altitude than at the surface. This picture would also be an example of low-level wind shear because we're only looking at the winds from the surface to around 6,000ft.
It's important to note the smoke tends to reach a certain height and stop. That's because the smoke has reached an inversion layer where the air temperature is actually increasing with altitude. This means the atmosphere is stable. You can actually read the sky without any fancy high-tech instruments. You can learn a lot by just looking up.
Fox6 Chief Meteorologist
Or shall I say, oh computer models... I could only find one model that at least showed a few clouds before 9AM but the NAM has us clearing out quickly this morning and I don't buy it. So yes, as a meteorologist we don't just rip and roar or believe what a model shows. We compare models to current data and go from there. So I made adjustments to the cloud cover and temperature forecast based on current conditions.
Overall, expect cloudy skies with some sunny breaks possible today and instead of widespread 60s we'll see widespread 50s.
So what's next?
MONDAY: We are most confident in this forecast with highs in the 60s, increasing clouds and the chance for showers increasing from west to east during the afternoon hours. Showers will wrap up before sunrise on Tuesday.
FRIDAY INTO SATURDAY: Uncertainty builds a bit with subtle long range model differences. The GFS is weaker with less precipitation than the stronger and wetter European model.
STORM SYSTEM AROUND THE 23RD: Models differ dramatically. The jet stream never phases and a cut off low develops across the Southwest according to the European model. The GFS model shows the jet stream phasing and a coastal storm developing.
This is normal for model error to increase the further you go out in time. We'll keep you posted as new model information comes in.
Jill Gilardi Fox 6 Meteorologist
The jet stream is fast flowing air that circulates around the globe. It separates warm air from cold air and causes storm systems to develop. The jet stream can flow from west to east, north to south or south to north and looks like a wave of troughs and ridges if you were to view it from space.
Computer models simulate troughs and ridges over time and typically you get stormy weather with troughs. On the eastern side of a trough, air diverges and rising motion is abundant and that's where you'll find most of your precipitation. So in the images below, notice the placement of the troughs and you'll see how it correlates to the precipitation forecast.
WEAK STORM SYSTEM #1: MONDAY-TUESDAY AM
Showers are possible across west Alabama on Monday afternoon. Best chance across central Alabama is during the evening and overnight hours. Overall, precipitation is expected to be light. 40% chance.
STRONGER SYSTEM ON FRIDAY INTO SATURDAY:
60% chance for showers and storms. A strong or severe threat is possible but too far out for many details regarding that seeing the models don't agree on the exact track of the surface low.
STRONG SYSTEM ON THE 22-23RD:
Jill Gilardi Fox 6 Meteorologist
You may have heard me mention on Fox6 News that we're heading into pattern with a more active and stronger jetstream. This will mean one storm system right after another impacting the area. Right now we're looking at three systems that could have impacts on our state over the next few weeks.
1) The first system will impact us late Monday into Tuesday. This mainly looks to be just a few showers and fairlyl short-lived. I don't see this one as any more than some rain after 3pm and lasting into the overnight. The heaviest rain fall will likely be north of I-20.
2) The second system will arrive around December 19th-20th and will be much stronger. This system could bring a round of thunderstorms to the area. We will likely see a surge of moisture and warmer air prior to its arrival and this will mean more instability. With the proximity of the associated low to our north, we will likely have a good bit of wind shear. I see the greatest potential for stronger thunderstorms with this second system.
3) The third system will arrive between December 22 and 24th. Right now - it appears to be rain. It should clear out by Christmas Eve with cooler and drier air present Christmas Day. We had seen some model hints at snowfall with this one, but so far so real consistency. This is still over 200 hours out so there's still a bit of dart board throwing on this one.
The Climate Prediction Center continues to indicate above average temperatures for the rest of December with above average precipitation.
Still - it appears the months of January, February, and March will remain colder than average. We are already seeing signs of a weak El Nino and this will have some impact our Winter weather. The deep freeze for Alabama is not likely to happen until January.
Have a great evening!
Fox6 Chief Meteorologist
I write up monthly crop/dairy related articles for a company called FCStone, eDairy and I thought I would share this month's article with you all seeing it's very interesting regarding the worst drought in over 1,200 years in California.
The state of California is experiencing the worst drought in at least 1,200 years according to scientists who analyze tree rings. According to the American Geophysical Union, it’s now drier in California than during the 1930s dust bowl and the historic droughts of the 1970s and 1980s. The scientists at the Woods Hole Oceanographic Institute and the University of Minnesota used tree rings to reconstruct the Golden State’s temperature and precipitation history dating back to 800 A.D., Washington Post reports. The method they applied was simple and vivid, with tighter rings on California’s oldest trees meaning dryer years. During the 1,200-year period, the researchers identified 66 droughts, which lasted between three to nine years. But none of them were as bad as the drought that started in California in 2012 and still far from coming to an end. Moreover, the trees revealed that 2014 turned out to be the worst single drought year in the surveyed period.
The current dry season was caused not only by low below-average precipitation, but also by record-breaking heat, which intensified the drought by around 36 per cent, the scientists said. More than 50 percent of California remains in exceptional drought. Bloomberg reports that water shortages as well as crop and pasture losses may cost the state 2.2 billion dollars this year and 428,000 acres of land left unplanted. Even with record rains, falling in California during the first week of December it wasn’t enough to seriously affect the situation. It’s too bad because more than a year’s supply of water has gone missing in the state’s reservoirs. It’ll take at least several unusually wet years to regain the losses.
What’s positive news? The precipitation outlook for the rest of this month looks above normal and there’s a good chance it will stay above normal through the winter of 2014/2015. 5-10 inches of rain could fall across the state between today and the 17th. The reason for the wetter pattern is called the pineapple express. It’s the non-technical term for a meteorological phenomenon characterized by and strong and persistent flow of atmospheric moisture and associated with heavy precipitation from the waters adjacent to the Hawaiian Islands and extending to any location along the Pacific coast of North America. The enhanced rainfall pattern is often present during an El Nino episode. There is an approximately 65% chance that El Nino conditions will develop this winter and last into the spring. So if El Nino conditions develop it will most likely be weak but even a weak one may help to enhance the pineapple express and rainfall across California.
Jill Gilardi Fox 6 Meteorologist
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