|WX AND TIME OF DAY: MORNING DAYLIGHT
METEOROLOGIST JEFF HABY
The next series of 5 Haby Hints will examine weather and time of day. The 5 time intervals that the writings will be broken down into include
morning daylight, afternoon, evening, early night and late night. The series will focus on generalities that can be expected in the weather for
each of these time periods. This first hint will examine morning daylight.
The morning daylight extends from when the sun comes up to local noon time. This range of time is going to depend on season and latitude since
sunrise time varies greatly depending on the season and latitude. In general, for many locations this time frame will start from between 5 to 8 am and
extend until noon. This 4 or so hour range of time can experience significant changes in the weather.
One generality is that the weather tends to be coolest during the early portion of this time frame. Often the overnight low temperature will
occur around sunrise. This is because cooling overnight is cumulative. With no solar radiation, the temperature cools during the night and
is not able to recover the dropping temperatures until the sun rises and gets high enough in the sky to start warming the surface.
Another generality is that the weather tends to be stable during the early portion of this time frame but decreases significantly in stability
by noon. Thunderstorms are not as common after sunrise due to it typically being too stable for storms to develop. The colder temperatures at
the surface help create an inversion which makes the lower troposphere stable. After sun rise, the increasing sun angle will help warm the
surface. By noon, the temperature can be significant warmer than it was at sunrise. Often the greatest temperature jump during the day occurs
in the morning hours. The much warmer temperatures at noon mean the troposphere is less stable or may even be unstable. Cumulus clouds will
often start developing once the conditions are unstable.
A third generality is that the wind tends to be light in the early portion of this time frame but quickly picks up in intensity by
late morning. The stable conditions contribute to lighter wind. On many mornings to start, the wind will be calm or nearly calm. Once
the sun rises and mixes out the cool and stable air right at the surface, wind speeds can pick up significantly.