Where Cold Fronts Come to Die

During the summer months, cold fronts usually have trouble moving through our part of the world and many times they stall and dissipate over our region or just south and east of here over the coastal Carolinas. This is due to several factors including the positioning of the jet stream and the strength of the Bermuda High. Also, the cool/dry air masses and their associated high pressure areas are not that forceful at this time of year. That is why the heat and humidity usually win out in Hampton Roads. Every so often though, a cool air mass will have enough of a push to make it here bringing a brief break to the heat and humidity. When the fronts do make it out to the Gulf Stream off the Southeastern Coastline, there is that possibility that a tropical cyclone could spin up if conditions are right. If there is an unusually strong high pressure area to the north, this could increase the possibility of tropical cyclone development. Once we get into September and October, the cool air masses start to become stronger and have more push, so they often begin to make it through our area with no problem. However, it all depends on the weather pattern at the time and the direction that the upper-level winds are blowing. If they are blowing SW to NE or parallel to the cold front, then the front will most likely stall out. If the upper-level winds are blowing NW to SE, the front should be able to push off the coast with no problem. There are times when the jet stream is too far north to push the fronts through the area.

Why are nights with a clear sky sometimes colder than nights that are cloudy?

Clouds act like a blanket and actually prevent the heat gained from the previous day from escaping out to space. Humidity levels throughout the atmosphere play a role, also. The lower the humidity, the more heat will radiate out into space. Other factors such as wind speed affect the temperature. On windy nights, the cold air (which is heavier than warm air) cannot collect at the surface. The wind keeps the air mixed preventing the heat from radiating into space. Now, if an arctic air mass is moving into your area, the advection of the cold air can be just as effective in bringing down temperatures to frigid levels. However, once the winds subside as the high pressure area moves in, the following night will usually be colder. Snow cover plays a role in surface temperatures as it reflects the sun’s light and heat during the day and produces ideal conditions for rapid heat loss at night.

Why does the size of snowflakes vary?

Did you ever wonder why snowflakes can be large and featherlike or very small? The reasons for the variability are complex but I’ll try to give you the basic reasons. First and foremost, if temperatures are marginal to create snow, the flakes will stick together due to the flakes being wetter and more “sticky”. Also, if humidity levels are high, they will tend to be larger. Wind speeds or the speed that the flakes are falling could also be a factor as stronger winds will tend to keep the flakes from sticking to one another. Electrical conditions in the atmosphere can play a role, also.