Th 011212

By: OrangeRoses , 1:39 PM GMT on January 12, 2012

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7 AM Thur. Jan 12 windchill 19 temp 29 wind NW 15 mph gust 20 mph

• Overnight the temp factor reached the freezing point at 1 AM
• the lagging temperature dropped to 32 at 4 AM.
• Peak 35 mph gusts many times

With average gusts 26 mph and steady winds of 17 mph it feels much colder.

8:18 PM
The windchill remained below 29° all day. Now the temperature is below freezing.

Overnight Forecast
Most likely, just before 7:25 AM sunrise, will be a Low Temp of 18° with a 5 mph wind that "feels like" 11° and is called windchill- the chill of the wind on your skin, hopefully you're wearing gloves, hat, heavy coat, thermal-lined or wool leggings, warm socks & no high heels. Remember, a higher wind and/or lower temp, lower windchill.


Friday Morning
The low temp I suggested in the overnight forecast above was 6° too low. In fact the lowpoint windchill of 18° and the low temp of 24° happened at 1 AM. Then both began to warm slightly until now - 7:40 AM. Source: Mesonet.org

Here is one possible reason - a NWS Observation:



National Weather Service Shreveport LA
349 am CST Friday Jan 13 2012


cirrus shield has begun to thicken this morning atop the Arctic air mass in place...ahead of the next progressive shortwave noted on the water vapor loop diving southeast across the plains and into the Texas/OK panhandles. While the cirrus should delay a progressive warmup this morning across the region...a gradual warming trend should commence by midday...as the cirrus begins to thin when the trough axis begins to move into the region.

My Comments: Radiational cooling is greater when there is less cloud cover. Most likely the cirrus cloud shield, although high thin paintstrokes, clumped together, insulating the lower atmosphere and, hence, the ground below. Less wind and less cooling accounted for the 6 degree difference mentioned above.


Saturday Morning Jan 14
The temperature dipped to freezing (32° F) at 8:50 PM last night, went up and down slightly 1 degree for about an hour, and then stayed below freezing until 8:50 AM this morning.
Source: Mesonet.org
This chill factor of 12 hours represents the longest timespan this year of 2012. So it should have cooled the ground enough to cause surface frost but underneath the chill data for 4 inch depth bare soil temp was 37° at 10 AM. Source: Mesonet.org Δt=15 min
In shady areas just 2 hours ago I spotted white frost outside my cold window.
[Once again the McCurtain County airport datafeed stopped this time at 5:55 AM, and remains frozen at 11:15]








∞ You learned and forgot ∞ Now I return with the winds howling low ∞
∞ Remember...show respect for the earth & sky ∞
∞ One more night for you to wonder why I am here ∞





Artwork by Josephine Wall josephinewall.com

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