Weather Fact of the Day

February 5 is National Weatherperson's Day, commemorating the birth of John Jeffries in 1744. Jeffries, one of America's first weather observers, began taking daily weather observations in Boston in 1774 and he took the first balloon observation in 1784. This is a day to recognize the men and women who collectively provide Americans with the best weather, water, and climate forecasts and warning services of any nation.

Lenticular clouds are formed when flowing air encounters obstructions (often mountains), causing the air to rise up the obstruction. This movement of air can form standing waves on the obstruction's opposite side. If the air in these standing waves reach dew point at the crest of a wave, allowing it's moisture to condense into clouds, a lenticular cloud may be formed.

Banner clouds occur when a strong wind blows over the steep peak of a mountain, causing the pressure to drop on the opposite side. This pressure drop can sometimes cool the air enough for it’s moisture to condense briefly into droplets or ice crystals.

Incus form in cumulonimbus clouds. As cumulonimbus rapidly grow to very large sizes, they can reach a point in the atmosphere of temperature inversion. This is when a region of warmer air blows over a region of cold air. This boundary usually occurs at the tropopause; the separation of the troposphere and stratosphere. This boundary then acts as a ceiling, stopping the vertical development of the cumulonimbus and causing it to spread out in an anvil shape.

These strange jellyfish-looking structures are made from precipitation which never reaches the ground due to evaporation. Virga can form at any cloud layer, but they are typically only composed of water droplets and have a grey appearance at lower levels. At higher altitudes, Virga are made of ice crystals and have a whiter hue. Occasionally, you can find Virga falling into a strong jet of air, causing them to bend at a 90 degree angle.

Lacunosus occurs when a layer of clouds develops holes, around which fringes of cloud form. This sight can materialize at all three cloud levels, but it is a very rare and short-lived formation. The holes in Lacunosus are caused by sinking pockets of air, and the cloud fringes occur when air rises up between the pockets to replace it. This sinking can take place when a layer of cold air is above a layer of warm air, making the denser, cold air sink into the layer of warm air.