When the hummingbirds began to arrive it was Hot August and extreme drought. There were no flowers in the fields for the birds and bees, so they were very hungry when they got here. When they leave, it will be after a cold front has made its way south. It is like they "bring in Fall". On September 21, we had the first significant, measurable rainfall in 4 months. The new herd that came in last week, left for Mexico and took their bees with them! On the 22nd, I was feeling a little sad that some of the birds left. All of a sudden a butterfly showed up at the feeder! The first butterfly of fall. More birds will be coming in and all will stay until the cold front. Enjoy your photostudies-the links to the G+Albums are below:
A cold front is defined as the leading edge of a cooler mass of air, replacing (at ground level) a warmer mass of air, which lies within a fairly sharp surface trough of low pressure. It forms in the wake of an extratropical cyclone, at the leading edge of its cold air advection pattern, which is also known as the cyclone's dry conveyor belt circulation. Temperature changes across the boundary can be as much as 30 °C(54 °F). When enough moisture is present, rain can occur along the boundary. If there is significant instability along the boundary, a narrow line of thunderstorms can form along the frontal zone. If instability is less, a broad shield of rain can move in behind the front, which increases the temperature difference across the boundary. They are stronger in the fall and spring transition seasons, and weakest during the summer. When they catch up with the preceding warm front, the portion of the boundary which does so is then known as an occluded front.
Development of cold front
|Weather phenomenon||Prior to the Passing of the Front||While the Front is Passing||After the Passing of the Front|
|Temperature||Warm||Cooling suddenly||Steadily cooling|
|Atmospheric pressure||Decreasing steadily||Lowest, then sudden increase||Increasing steadily|
|Precipitation/conditions*||Light patchy rain can be produced by stratocumulus or stratus in the warm sector. In summer, sometimes thunderstorms if a preceding squall line is present.||Prolonged rain (nimbostratus) orthunderstorms(cumulonimbus): depends on conditions.||Showers, then clearing|
|Clouds*||Often preceded by cirrus, cirrostratus then altostratus like a warm front (but usually with smaller amounts of these clouds). Areas of cirrocumulus and altocumulus within cirrostratus and altostratus more commonly seen than at a warm front. Larger cumulus clouds under the higher cloud types than at a warm front, where stratocumulus and cumulus humilis usually occur. Some of these cumulus clouds may produce showers ahead of the front.||Cumulonimbus and cumulus congestus producing frequent showers, with a sheet of upper altostratus, through which the sun can sometimes be seen. Less commonly nimbostratus occurs with continuous rain.||Patchy altocumulusor stratocumulus and higher cirrus clouds along with fast moving stratus fractus then eventually scatteredcumulus and sometimescumulonimbus.|
|Visibility*||Fair to poor in haze||Poor, but improving||Good, except in showers|
|Dew Point||High; steady||Sudden drop||Falling|
Characteristics of boundaries around an extratropical cyclone
Thanks to G+ Awesome Auto BackUp, here are some highlights from these albums!
...this is brendasue signing off from Rainbow Creek. See You next time! I hope You have been inspired to begin feeding birds! Love is contagious!