Archive for August, 2012

A COLD FRONT CAUSES UNSETTLED WEATHER ON SATURDAY… ANOTHER SYSTEM MAY BRING RAIN ON MONDAY, BUT THE EXTENDED FORECAST IS VERY UNCERTAIN

A cold front is currently entering the area and it may bring us some showers and thunderstorms today. The forecast today is very uncertain both for the short term and the extended period. I don’t think that forecasters are confident as to how much rainfall we will see today. The cloudy conditions this morning will probably inhibit the severe weather potential since with limited sunshine, we won’t heat up too much. However, with such high levels of humidity around, any shower/storm could produce heavy rainfall. The National Weather Service has a 70% chance of rainfall on Saturday. On Sunday, we should see improving conditions, but with the front just offshore, a shower or storm is still possible. Then, the forecast gets real interesting. Low pressure is expected to develop nearby on Monday and some models indicate that we will get a good dose of rain. Other models aren’t as aggressive with the rain. And, even the extended forecast is quite uncertain as the models can’t agree on how a general trough over the eastern states will affect our local weather…. Although the tropical Atlantic has become active, there are no immediate threats to the East Coast. Hurricane Gordon is moving east and may actually affect Portugal and Spain. Tropical Storm Helene formed in the southwestern Gulf of Mexico and will move into Mexico today. Another system way out in the eastern North Atlantic may eventually become a formidable system that will have to be watched very closely. However, we have plenty of time before it could become a threat to the East Coast, if it ever does. I will have an update on Sunday.

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THE FRONT WHICH HAS BEEN TRIGGERING SHOWERS AND STORMS THE PAST FEW DAYS STRUGGLES TO FINALLY PUSH OFFSHORE… THE TROPICS ARE QUIET FOR NOW

Late Saturday afternoon and evening, a line of moderate to heavy rain moved through Hampton Roads. There was no lightning or thunder in my neighborhood. Around a half inch of rain fell in my backyard. The frontal system that has been responsible for the unsettled weather of late is finally going to limp offshore but not before bringing yet another day with a chance of showers and thunderstorms. Forecasters are saying that the chances of rain today (Sunday) are lower than what they were on Saturday. The further southeast you are, the greater the chances of rain. On Monday, the front should be just offshore and weakening, but a sea breeze might be enough to set off an isolated shower/storm. Another front may bring another chance of a round of showers/storms Tuesday into early Wednesday. Odds are that the coverage and duration won’t be as high as it was the past few days. Fronts have a very tough time moving through our part of the country at this time of year. Some of the reasons for that are the Bermuda High pressure off the Southeast Coast and the normally weak upper-level flow… The tropical Atlantic has quieted down for now but we are soon going to be entering the time of year when conditions should improve for tropical cyclone development. Right now, it seems that dry air, wind shear, and overall stable conditions are combining to inhibit tropical cyclone development. The water is plenty warm enough to sustain a hurricane so once the hindering factors are gone, it will be very interesting to see how active it will become. That’s it for now. Have a great day.

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SHOWERS AND THUNDERSTORMS ARE POSSIBLE ON SATURDAY… RAIN CHANCES LOWER EARLY NEXT WEEK

The weather map this Saturday morning features an occluded low pressure system over the Great Lakes with a cold front extending southward through central Virginia. This front will be our weather maker this weekend as it stalls just west of Hampton Roads. Although the risk of severe weather is relatively low, the high level of moisture flowing in from the southwest will maintain the threat for heavy rainfall. However, forecasters don’t think that it will be widespread, just some isolated pockets of heavy rain. Some rain showers moved through Friday evening but I did not receive a lot of rainfall in my neighborhood. Actually, Friday wasn’t as stormy in most areas of Eastern Virginia as forecasters originally thought. Most of the stormy weather was up in the Northeast. Rain chances are expected to lower somewhat on Sunday. Early next week, we should be dry for the most part with seasonal temperatures. An isolated storm will be possible, however. In the tropics, TD 7 will enter the Caribbean Sea and its future is very uncertain. Increasing shear may prevent it from becoming a hurricane but intensity forecasts are not that dependable. We’ll see whether it can overcome a hostile environment. I’ll have an update tomorrow morning.

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AN UNSETTLED PERIOD OF WEATHER MAY BE ON WAY… TROPICAL STORM ERNESTO IS STRUGGLING DUE TO SHEAR AND DRY AIR ENTERING ITS CIRCULATION… TROPICAL STORM FLORENCE MAY FACE THE SAME CONDITIONS IN A FEW DAYS

I love to watch the sky on days like today, when we are under the influence of the Bermuda High. The sky is a deep blue with large puffy white cumulus clouds passing by. Sometimes in patterns like this, those clouds build to a point where they create showers and thunderstorms. With the high pressure in control today (Sunday), rain chances are expected to remain relatively low. However, there may be a shower or storm over some areas. Any rain could be heavy as there is a large amount of water vapor in the air, hence the dew point in the low to mid seventies. Rain chances are expected to ramp up on Monday as a cold front destabilizes the atmosphere. Although the front is not especially strong and will actually be weakening over time, it should be enough to cause showers and storms which is why the National Weather Service has raised rainfall chances to 60% on Monday. Rain chances will remain slightly elevated for a few days as the front is expected to stall somewhere close by. The front will eventually dissipate which is typical for this time of year… Regarding the tropics, Tropical Storm Ernesto is battling wind shear and dry air, which has become entrained in its circulation. What about its track? Many times, when storms remain weak, they take a more westerly track vice west-northwesterly track. This is because storms that are weaker do not extend as high into the atmosphere and are less affected by the steering flow that would move them further north. So, there is some uncertainty as to where Ernesto will eventually end up. As I said in my Saturday post, anyone along the Gulf Coast or on the Yucatan Peninsula needs to monitor this storm. Florence may encounter the same problems that Ernesto is experiencing now according to the computer models. Florence developed at a higher latitude so it may be more influenced by the westerlies. You should monitor this storm but forecasters have plenty of time to watch it. That’s it for now. Have a great day.

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THE BERMUDA HIGH WILL BRING US MORE OF THE SAME… WARM AND HUMID WITH JUST A CHANCE OF SHOWER OR THUNDERSTORM IN SPOTS… TROPICAL STORM ERNESTO MOVES WESTWARD ACROSS THE CARIBBEAN SEA

The weather pattern over the next few days will feature high pressure to our east (referred to as the Bermuda High) creating a light southerly flow which will continue to bring up warm and humid air. While there are no major systems or disturbances nearby to spark showers or thunderstorms, it is so humid that any little trigger can result in convection such as a sea breeze boundary. The National Weather Service only has the chance of rain at 20% which means that most of us will not see rain each day this weekend but a few of us could have a heavy downpour or thunderstorm. The highest chances in a pattern like this are normally in the afternoon and early evening hours. A cold front will be slowly moving towards the Mid-Atlantic States early next week but will be weakening as it comes closer to our region. Rain chances will go up a bit early next week. This time of year, it is very hard for cold fronts to make progress south and east as the Bermuda High is normally very strong and does not allow these fronts to move that far south. In addition, the cool, dry air behind the front has less of a push this time of year…. What about the tropics? Well, Tropical Storm Ernesto is moving westward across the Caribbean Sea and it may become a hurricane this weekend. Folks on the Yucatan Peninsula and along the Gulf of Mexico should pay close attention to this storm as it moves west.  I just learned that we have a new tropical storm in the Eastern North Atlantic Ocean and that would be Florence. There is also an area over the Bahamas that has to be watched for development but right now, the National Hurricane Center is saying that it is very disorganized and will take a while before anything develops. So, the tropics have come alive and since it is now early August, that is no surprise. This is the time when you should have your hurricane emergency plans in place should a storm threaten your area. I will have an update on Sunday.

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