Snapshot of the Start of Spring

Winter is over. Spring started officially at 7:44am. Today is the day that the sun is directly overhead at the equator. From this point on the sun’s apparent position in the sky will move farther north and provide longer daylight hours in the northern hemisphere.

Using BWI-Marshall Airport as a reference point, the sun rose today at 7:11 and will set at 7:18. That is 12 hours and 8 minutes of sunlight. The equinox is the halfway point and is supposed to denote equal hours of night and day. This is based on the center of the sun aligning with the horizon at rise and set. The extra 8 minutes of daylight comes from the fact that, at sunrise, the outer edge of the sun crosses the horizon a few minutes before(or after in the case of sunset) the center-point does.

In Baltimore, on this first day of spring, the average high temperature is 55 degrees and the average low is 35. The passage of a cold front yesterday has brought some unseasonably chilly air into the region but readings are expected to rebound nicely over the weekend.

Tom mentioned in the previous blog entry that the area is running a little short on precipitation. In that respect the news is not great. Any significant rainfall chances for the first week of spring are pretty slim.

Weatherwise, the satellite image below shows the equinox weather over the western hemisphere.

latestfullCourtesy: NASA

The two satellite images below demonstrate the warming effect of the longer hours and higher angle of sunlight in the month of March.

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The image above show the ice-pack on Lake Superior in early March. The image below shows the diminished ice-pack as of this morning.

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On the flip side of all of this, it is the first day of autumn in the southern hemisphere. There the days will be growing shorter. It is also interesting to note that the tropical cyclone season is very active at this time in the southwest Pacific and Indian Oceans, similar to the tropical storm and hurricane activity spike in the Atlantic Basin in September and October. The satellite image below shows two such storms now active near Australia.

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A close-up image (below) of Ilsa transmitted the day after the above image shows that the storm has become quite impressive.

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John Collins

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