Could It Be as Cold Tomorrow Morning? And, Grower Feedback From Last night…(Jan. 7, 2014)

— Written By Barclay Poling

Good morning!

Hopefully everyone kept the heater in their house running last night and this morning? I was especially concerned for the folks up in the Mountains last night. Take a look at the temperature dive that took place in Haywood County (Fig. 1). They are stil at – 9 F at 8 a.m. today! Between 4 and 5 a.m. they  hit -16.1 F.

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haywood county

Fig. 1. Graph produced by State Climate Office – this site is a Remote Automated Weather Station, that is in Haywood County, NC (latitude 35.6494, longitude -82.9131, elevation 5291 ft above sea level).

Over in the Central Piedmont it went below 10 F in locations like Siler City (location of Michael Beal’s farm, former President NCSA). I have not had a chance to go back and download the latest Temp graph for Siler City since about 5 a.m., but here is what I saw a little earlier this mornng (Fig. 2)

siler city

Fig. 2. In Siler City the mercury dropped about 47 degrees in 12 hours. At 4 p.m. (Jan 6) it was 56.5 F, and then at  4 a.m. this morning it was 9 F. At 7:35 a.m. it was 7.2 F.

I ran out briefly at my house in N. Raleigh into the frigid cold to retrieve our newspaper at 7 a.m., and saw that we were a tad below 10 F (Fig. 3)

tad below 10

Fig. 3. At my home in N. Raleigh I have been amazed over the years how accurate this inexpensive Taylor on my deck is! I just checked the official low for my area, and it was 9 degrees.

5 a.m. accurate

Fig. 4. This is the temperature map for our region at 5 a.m. today!

916 a.m. intellicast

Fig. 5. At 9:16 a.m. this was the temperature map, and it surprised me “how little” the mercury has moved since before sunrise. Raleigh only moved 1 F from  5 a.m. – 9 a.m. Our high for Raleigh today will only be 23 F. We will not break above 15 F until 10 a.m. At 4 p.m. we will hit our high of 23 F, and we are looking at a low of 15 F for tomorrow morning, which you would think is better than this morning? But, at the ground level tomorrow morning, it could actually be just as cold as today!

So, how cold will it be at the strawberry plant level on Wed. morning?

Condtions tonight will  favor strong radiative cooling at the ground level, and I expect that the air temperature at the strawberry plant  level will be significantly lower than the air temperature at 6.5 ft (weather shelter height).

SkyBit (below) shows it will be 9 F at the ground vs. 15 F at 6.5 ft.

It is not often that we see differences of this magnitude between canopy level temperatures (near the ground), and the air temperature at 6.5 ft (2 m). What this means to you is that the forecast in your area for minimum temperatures tomorrow morning will likely be 5-6 F warmer than the air temperature at the strawberry canopy level! So, be sure to leave those covers ON today! Under sunny conditions today, the covers will also help to build up the ‘heat reservoir’ for going into another very very cold night.

SkyBit for Clayton (issued at 7 a.m. today): 

skybit jan 7

Accuracy check.

Periodically, I like to examine SkyBit’s accuracy at Clayton Central Crops against the State Climate Office’s recordings for air temp. The SCO has a weather station right at this research station, and their readings appear in the second column below (actual). In the first column, are the temperatures that were being forecast by SkyBit yesterday at 5 p.m. (for weather shelter height). In the third column, you can compare the difference between the forecast and actual temperature. Please note at 7 a.m. this morning that Skybit air temp  forecast was for 11 F, and the actual was 11.5 (the actual was 0.5 higher). However, the canopy forecast that SkyBit made for this morning was 8 F (see the SkyBit below the next chart -this is the forecast SkyBit made at 7 p.m. Jan 6). If we go back and reduce the air temperatures at 6.5 ft by 3 F, to reflect colder canopy conditions, you see the result in Col. 4. All in all, I think this was a very good forecast by Skybit for weather shelter height compared to State Climate Office data, and I may be able to retrieve some actual canopy data from researchers at Clayton for this morning to see how accurate they were in forecasting 8 F at strawberry level?

Col 1 Col 2 Col 3 Col 4 Col 5
Jan 7 2014 SCO Temps SkyBit Air^ Dif. 1 SkyBit Can.^ Dif. 2
12:00 a.m. 20.4 23 -2.6 20 0.4
1:00 a.m. 17.9 21 -3.1 18 -0.1
2:00 a.m. 16 20 -4 17 -1
3:00 a.m. 14.9 18 -3.1 15 -0.1
4:00 a.m. 14.4 16 -1.6 13 1.4
5:00 a.m. 13.5 14 -0.5 11 2.5
6:00 a.m. 12.4 12 0.4 9 3.4
7:00 a.m. 11.5 11 0.5 8 3.5
8:00 a.m. 10.9 14 -3.1 11 -0.1
9:00 a.m. 11.1 16 -4.9 13 -1.9
^ the SkyBit minimum canopy forecast for Jan 7 showed 8 F vs. 11 F air temp min at 7 a.m.
This was a 3 F difference that was used to calculate an adjusted Canopy temp in Col. 5

skybit 7 p.m. Jan 6

Above is the SkyBit issued last night at 7 p.m. for today. The air temp forecast for this morning by SkyBit was 11 F at 7 a.m. (see the table on bottom at 7 a.m. for the Temp number). The official air temp at Clayton this morning was 11.5 F at 7 a.m. (so, SkyBit was pretty darn close). Of course, the thing that SkyBit does that is unique to their forecast, is also provide the grower with a strawberry canopy minimum temperature, and that was for 8 F this morning at 7 a.m. (I will try to obtain info from researchers at Clayton what the actual temp was at the canopy this morning). Tonight, Skybit is forecasting a minimum of 9 F in the canopy, and an air temp of 15 tomorrow morning. It would appear that it is going to be just as cold tonight!

Grower feedback from last night:

Scott Dail, Conetoe (Edgecombe Co)

Good morning Dr Poling just wanted to send you some temp info I collected early this morning. I checked temps at 630 and it was 17 outside of the covers which was much warmer than forecast. Under a 1.2 oz cover was 28 and a 1oz was 23 so I think we came out really good.

 please feel free to submit information about what happened at your farm last night and this morning! 

Clarification on Record Low Numbers:

I had this email exchange with the State Climate Office re: Record Lows this morning:

My Question to Rebecca Cumbie with SCO, NCSU:

“I am a little confused by N&O reporting a record low of 7 F for 1924 on Jan  6th (yesterday). Then, if you examine the historic lows in AccuWeather Pro database for Raleigh, NC, they indicate that 9 F is the record for Jan 6th (1969).

I am unsure which is correct? Help!”

Rebecca’s reply:

Good Morning, Barclay,

It looks like these are reporting record lows for Jan 6 from two different COOP stations:
Raleigh 4 Sw COOP station (ID: 317074) has a record low of 7F that occurred in 1924
and Raleigh Airport COOP station (ID: 317069) has a record low of 9F that occurred in 1969. Technically, both of these are correct but they are misleading since these records are for individual stations.

Looking at Jan 7, the records for these two stations are:
14F for Raleigh 4 Sw, which occurred in 1988, and 15F for Raleigh Airport, which also occurred in 1988.

I found these values on the Weather Extremes page on our website and verified them against the NCDC Daily Lowest Min Records tool. I hopes this helps shed some light, please feel free to let me know if you have any more questions.

Rebecca
Rebecca Cumbie
Extension Climatologist
State Climate Office of North Carolina
rvcumbie@ncsu.edu
919-513-2444

Have a good day!

Barclay

p.s. it is still only 14 F on my deck in N. Raleigh, and it is now 11:30 a.m.!

Dr. E. Barclay Poling
Professor Emeritus
Department of Horticultural Science

Campus Box 7609, 162A Kilgore Hall

NC State University
Raleigh, NC 27695-7609