Grower Comments This Morning & Freeze Warning in Effect Tonight (9:40am, 3/28/15)
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Fig. 1. Minimum temp map for Sunday morning in NC. Records may not fall, but temperatures will be in the low 20s across much of NC piedmont.
Fig. 2. I sent this map out last night. One disturbing development is the extension of the YELLOW band through all the mountains (Fig 1). The yellow = 18-20 F.
Fig. 3. Photo taken before sunrise today, and shows a clearing sky…clouds last night kept frost from forming in many areas. Even so, after sunrise there were “frozen beads” on my car hood, but no frost on the ground in N. Raleigh, NC. However, there is a NWS Freeze Warning in effect for tonight, and here is what growers are saying about it…
Tom Baker, VA Beach (8:35 a.m.)
“Well it ain’t gettin’ better! SkyBit forecast history for minimum Sunday canopy temps (down then up then down again and again and again):
Monday a.m. – 33
Monday p.m. – 33
Tuesday a.m. – 24
Tuesday p.m. – 24
Wednesday a.m. – 29
Wednesday p.m. – 29
Thursday a.m. – 26
Thursday p.m. – 26
Friday a.m. – 25
Friday p.m. – 25
This morning – 22 !!!
Fig. 4. This graph shows a plot of Tom’s data over this past week, and what I find really disturbing about this cold event is that the actual trendline is definitely downward, and it would not surprise me at all if the ACTUAL Sunday morning SkyBit is a few degrees lower than 22 F. So, that might mean 20 F, or even 19 F. Who can say??
Editor’s comment: I have seen a similar up and down forecast for tomorrow morning at Clayton (we are now looking at 22 canopy/25 air for 3/29), and we will be reaching what may be the same minimum in Clayton as Tom Baker in VA Beach!
Tom left several rows of Camarosa uncovered, but now plans to cover them up as well: ” We’re letting our last two “furrowed” row covers (for the Camarosas in Chesapeake) dry until early afternoon, then we’ll go have “too much fun.” AccuW says winds at 1 p.m. will be 15 gusting to 23 and we’ve got to pull the covers into the wind! L Glad there are only two left to pull!
Table 1. Chesapeake Detailed Forecast (AWIS)
Actual AWIS forecast for Chesapeake (near VA Beach). Note the remarkable drop in dewpoint temperatures tomorrow morning AFTER SUNRISE. Sunrise DP = 18 F; then at 11 a.m. DP = 10 F. For anyone who is doing sprinkling alone, this represents an extremely dangerous situation! Anyone doing irrigation alone must run the sprinklers until wet bulb (WETB) reaches at least 31 F. But, note that this will not occur in Chesapeake until 1300 (1 p.m.). Sorry about that! This may be enough to get even the most die hard anti-row cover growers to consider using row covers? And, while you are at it, buy a digital thermometer as well! The digital tells you when the blossom is safe. When actual blossom temperature reaches 31-32 F, you can shut down. But, the only way to determine the blossom temp is to have a digital thermometer with thermocouple that is inserted in bloom (like below)
Figs. 5-6. Accurate blossom temperature readings can be taken with a digital thermometer with thermocouple inserted in bloom. I recently priced a unit at Omega (see quote below). The HH 200A is actually a little less expensive than the HH 21A that the VA growers got as part of VDACS Block Grant in 2012. It should work just as well. The unit in above picture is reading 29.6 F. That is not warm enough! I will not shut down watering until the blossom temp registers 31-32. This unit is essential to all strawberry growers who are sprinkling on top of covers, or using drip underneath the cover to add some heating. If you are doing sprinkler irrigation alone, it can tell you when the blossoms are too cold. And, a reading of 29.6 would tell me you are getting pretty darn close to a serious problem, and need to increase precipitation rate immediately!
Here is quote I recently got on HH 200A model:
Piedmont, NC: some growers see few blooms, and may still be undecided about what to do? Maybe nothing?
“Nothing up here to really protect yet. One bloom here and there with a few starting up still covered by the plant. Not even popcorn yet.
31 at the house this morning with 28 at the field with ice.
Looking like we are gonna be a little late, as I figured with the cold February.”
Editor’s comment: I can sort of see the rationale of doing nothing tonight from the standpoint of just how difficult it will be to use sprinkler irrigation to protect those emerged flower buds, BUT the critical temp table below is not just my invention (beneath the photo), AND it represents the combined experience of strawberry researchers and growers over the last 3 decades. The table tells us to be concerned about temperatures below 25 F for the emerged flower buds. The grower who sent me the note about possibly not doing anything is going to probably experience a minimum Sunday morning of 24 F tonight (air temp), and I am guessing his canopy will be several degrees colder (based on my Clayton SkyBit). The emerged flower buds may be able to survive this? I don’t know for sure. I do know all open blossoms will be killed. Anyway, we may soon learn if the emerged buds can handle low 20s without injury?
Fig. 7. If the emerged flower buds are damaged by the cold tonight, this could delay your season opener by maybe another week
(7 a.m.) Frozen covers in Easley, SC:
Although everyone is interested in how late the season may be, some growers are more immediately concerned about how their covers got soaked late yesterday, and then froze up last night…the worry is about any damage underneath?
So, I am anticipating some reports today from growers in areas where this actually happened.
Eric Hunter, Easley wrote this morning:
“We are at 28 right now (7 a.m.). The covers are frozen as well as the grass in the fields. The covers didn’t have sufficient time to dry off. Hopefully everything is ok underneath. Our SkyBit just arrived and it has dropped us down to 20 degrees for tonight. Will the 1.25 oz. covers at the other land still be sufficient for that? I assume I definitely need to run drip irrigation if the covers are to be left on?”
Editor’s reply: No, the 1.25 oz will not protect open blooms with a low in canopy of 20 F, and I recommend sprinkling on top of covers tonight (see photo below), or consider the drip irrigation technique that a number of growers who do not have irrigation are using to add some extra heat when the row cover alone will not be adequate.
Fig. 8. When row covers are not enough, and growers have sprinkler irrigation systems, a favorite technique is to sprinkle on top of covers – see this advisory for more details: https://strawberries.ces.ncsu.edu/2015/03/va-update-on-white-frost-saturday-and-black-frost-sunday-noon-fri-32715/ (scroll down to where you can see the discussion about situations when row covers may not be enough). This same advisory mentions the dripping under the cover technique for producers who do not have sprinkler systems. You should read it!
Fig. 9. This was included in yesterday’s advisory. A 1.25 oz cover (med) is not going to protect all the way to 22 F. It is possible that emerged flower buds will be fine without a cover down to low 20s, but below 22 F it is anyone’s guess? Certainly, if you have some row covers, they should be applied TODAY unless you wish to conduct a science experiment tonight?
Editor’s comment on actual losses we’ve actually seen at 20.6 F with just row cover protection alone (1.2 oz cover):
Everyone has a different tolerance for risk. But, after running an experiment two years ago in March at Clayton, we learned that with a minimum temp of around 20.6 F that about 25% of the open blossoms beneath the covers were damaged, but another 75% lived.
You can read this report:
http://strawberries.ces.ncsu.edu/2014/03/how-much-of-a-safety-margin-does-a-row-cover-provide-march-26-2014/
12:10 p.m. comments from Eric Hunter: I’ve looked underneath the covers and everything seems to be in good shape. There are some occasional blooms that had contact with the row cover that didn’t survive, but otherwise no problems.
I have decided to double up on row covers instead of running drip underneath, and instead of sprinkling on top of the covers. My biggest concern with sprinkling on top of the covers is that it would take until at least Monday and possibly even Tuesday for the mass of ice to melt and the covers to dry out.
4:17 p.m. So here is what we did. We doubled covered everywhere we had a 1.25 oz. cover with a 1.5 oz. cover, essentially giving us a 2.75 oz. blanket. Surely that will be more than enough. Where we already had a 1.5 oz. cover, we left as is – I think that will be sufficient as well. During the winter, our 1.5 oz. cover gave us 10-12 degrees of extra warmth. Hopefully that will hold true as well tonight.
Some local forecasts have inched upwards a degree or two, NOAA has came down a degree, and AccuWeather went up a degree (I think), so it’ll be interesting to see what SkyBit says this evening. I expect it to stay about where it was (20). Looking at the big picture of everything, I totally expect to be at 19-20 tonight.
Blooms underneath the covers did well from last night. The uncovered plants do not have any surviving open blooms, but the unopened blossoms are fine.
Also, as an interesting side note, going back over our 18 year history with strawberries – this particular time frame (May 27th-April 5th) – we have around a 70% chance encountering a freeze. Three of our worst cold snaps have come between those dates (the lowest temps were at 15), with two of them being the same as the dates this weekend
Snow in Central VA this morning?
Fig. 10. This is actually an older file photo, but I did see that AccuWeather had a forecast of SNOW this morning at 9 a.m. in Central VA!
AccuWeather for Moseley, VA:
Fig. 11. Forecast showing snow in Central VA this morning.
Growers worried about duration of sprinkler irrigation cycle (could be 17+ hours)
I heard from Mike Wilder this early morning about the prospect that growers would need to start their irrigation systems so early this evening (like 6 p.m.) in many areas (when wet bulb reaches 31 F), and then he and I were going back an forth about how late into the day tomorrow they need to run (maybe as late as 11:30 a.m. in some western piedmont locations where the dewpoint will keep dropping after sunrise and be in the single digits by mid-morning — something I can’t remember over 30 + years of ever happening before). Anyway, here was Mike’s comment:
“Blueberries will need protection tonight in our area also. Grower pumps will get a real workout.”
Editor’s note: here is an example of a western piedmont location where the spinkling will need to start at about 5:30 p.m., and will have to run continuously through about 11 a.m. tomorrow (if you irrigate on a row cover, you don’t have to run nearly so long…just check your digital thermometer for bloom temp, and when the bloom is getting to 32 F, it is time to shut down…sadly, I am finding very few growers outside of VA have digital thermometers?)
Fig. 12. Western Piedmont Location: note the wet bulb is 31 at 5 p.m.
Fig. 13. Western Piedmont Location: note the wet bulb doesn’t get back to 32 until 11 a.m. So, a grower using sprinkler irrigation to control this freeze event would need to start at about 5:30 p.m. and run continuously until 10:30-11 a.m. Sunday (~16-17 hrs)
Be sure you run enough water! If you see ice getting cloudy, or with bubbles, increase pump pressure.
Fig. 14. You want clear ice in the morning!
Table 2. Consult with YOUR irrigation dealer today if you are unsure about the capability of your sprinkler system to handle different wind speeds and low dewpoints. In this table, you can see that with a minimum of 20 F and winds of 5-8 mph, you need to pump over 1/3rd inch per hour (that’s a lot of water). Very few growers are set up to handle these kinds of extremes with just irrigation, and so sprinkling on row covers makes a whole lot more sense! Consult this advisory for some pointers on sprinkling over top row covers: https://strawberries.ces.ncsu.edu/2015/03/va-update-on-white-frost-saturday-and-black-frost-sunday-noon-fri-32715/ (scroll down to where you can see the discussion about situations when row covers may not be enough). It is a good idea to review this leaflet as well for growers just using irrigation: StrawberryPlasticulureAdvisoryApril1505
Fig. 15. Checking nozzles before this hard freeze (see AWIS advisory next) to see if you have he right orifice size. You may need to “nozzle up” before tonight!
Freeze advisory in effect (North Carolina)
AWIS Weather Services, Inc. North Carolina Frost/Freeze Forecast Produced at 515 a.m. CDT on Sat Mar 28 2015 ... Forecast for Tonight ... Northeast NC Coast Currituck/Camden/Pasquotank/Tyrrell Counties **** HARD FREEZE **** ** PATCHY FROST PROTECTED AREAS ** Lowest Temperatures: 24 - 32 Elizabeth_City Min 24 Durations at/below 32: 1 - 11 Durations at/below 28: 0 - 6 Range Dewpoint Temps: 15 - 28 Range Wetbulb Temps: 25 - 37 AVG Wind Direction/Speed: NW 8 AVG Sky Condition: Clear Extended Forecast: Range of Lowest Min Temperatures in the Above Zones Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets) 03/30/15 03/31/15 04/01/15 04/02/15 04/03/15 04/04/15 -------- -------- -------- -------- -------- -------- 35 - 41 40 - 47 44 - 51 50 - 56 52 - 58 44 - 52 -------- East Central/SE NC Coast Carteret/Pamlico Counties **** HARD FREEZE **** ** PATCHY FROST PROTECTED AREAS ** Lowest Temperatures: 26 - 30 Morehead_City Min 29 Durations at/below 32: 4 - 9 Durations at/below 28: 0 - 3 Range Dewpoint Temps: 20 - 26 Range Wetbulb Temps: 25 - 35 AVG Wind Direction/Speed: NW 7 AVG Sky Condition: Clear Extended Forecast: Range of Lowest Min Temperatures in the Above Zones Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets) 03/30/15 03/31/15 04/01/15 04/02/15 04/03/15 04/04/15 -------- -------- -------- -------- -------- -------- 32 - 38 45 - 45 46 - 48 52 - 55 54 - 58 47 - 50 -------- Southeast NC NWS FORECAST ZONES 87-90,96-101 **** HARD FREEZE **** ** PATCHY FROST COLDEST PROTECTED AREAS ** Lowest Temperatures: 24 - 29 Elizabethtown Min 27 Durations at/below 32: 4 - 9 Durations at/below 28: 0 - 4 Range Dewpoint Temps: 14 - 26 Range Wetbulb Temps: 23 - 37 AVG Wind Direction/Speed: NW 7 AVG Sky Condition: Clear Extended Forecast: Range of Lowest Min Temperatures in the Above Zones Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets) 03/30/15 03/31/15 04/01/15 04/02/15 04/03/15 04/04/15 -------- -------- -------- -------- -------- -------- 34 - 41 39 - 45 45 - 49 52 - 55 55 - 59 46 - 50 -------- North-Central NC Franklin County Area **** HARD FREEZE **** **** LITTLE IF ANY FROST **** Lowest Temperatures: 20 - 26 Louisburg Min 20 Durations at/below 32: 8 - 13 Durations at/below 28: 3 - 9 Range Dewpoint Temps: 8 - 13 Range Wetbulb Temps: 19 - 28 AVG Wind Direction/Speed: NW 4 Long Periods of Calm AVG Sky Condition: Clear Extended Forecast: Range of Lowest Min Temperatures in the Above Zones Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets) 03/30/15 03/31/15 04/01/15 04/02/15 04/03/15 04/04/15 -------- -------- -------- -------- -------- -------- 33 - 42 34 - 42 43 - 50 47 - 53 52 - 57 40 - 47 -------- North/Central NC Alamance County Area **** HARD FREEZE **** **** LITTLE/NO FROST DUE TO DRY AIR **** Lowest Temperatures: 22 - 26 Graham_AG Min 24 Durations at/below 32: 9 - 12 Durations at/below 28: 3 - 8 Range Dewpoint Temps: 4 - 13 Range Wetbulb Temps: 19 - 28 AVG Wind Direction/Speed: NW 4 Long Periods of Calm AVG Sky Condition: Clear Extended Forecast: Range of Lowest Min Temperatures in the Above Zones Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets) 03/30/15 03/31/15 04/01/15 04/02/15 04/03/15 04/04/15 -------- -------- -------- -------- -------- -------- 35 - 42 36 - 41 45 - 50 48 - 53 53 - 58 40 - 46 -------- South/Central NC Richmond County Area **** HARD FREEZE **** ** PATCHY FROST PROTECTED AREAS ** Lowest Temperatures: 25 - 27 Ellerbe Min 27 Durations at/below 32: 7 - 8 Durations at/below 28: 2 - 4 Range Dewpoint Temps: 12 - 20 Range Wetbulb Temps: 23 - 30 AVG Wind Direction/Speed: NW 7 AVG Sky Condition: Clear Extended Forecast: Range of Lowest Min Temperatures in the Above Zones Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets) 03/30/15 03/31/15 04/01/15 04/02/15 04/03/15 04/04/15 -------- -------- -------- -------- -------- -------- 37 - 41 38 - 42 45 - 50 52 - 54 53 - 57 41 - 48 -------- Interior/EC-SE NC Wayne County Area **** HARD FREEZE **** ** PATCHY FROST COLDEST PROTECTED AREAS ** Lowest Temperatures: 25 - 27 Goldsboro_AG Min 27 Durations at/below 32: 6 - 9 Durations at/below 28: 2 - 4 Range Dewpoint Temps: 18 - 19 Range Wetbulb Temps: 24 - 33 AVG Wind Direction/Speed: NW 6 AVG Sky Condition: Clear Extended Forecast: Range of Lowest Min Temperatures in the Above Zones Min Temps Valid For Morning of Given Date (May NOT include ALL cold pockets) 03/30/15 03/31/15 04/01/15 04/02/15 04/03/15 04/04/15 -------- -------- -------- -------- -------- -------- 33 - 38 40 - 43 44 - 46 50 - 54 53 - 57 45 - 49 -------- For more detailed information visit www.awis.com or call 888-798-9955. Copyright 2015 AWIS Weather Services, Inc. All rights reserved.
For growers who do not have access to hourly wet bulb information, you may wish to consult the location nearest you for this information NOW.
NC Detailed Hourly Info: AWIS NC Mar 28-Apr 3
10-DAY DETAILED HOURLY WEATHER FORECASTS
SC Detailed Info: AWIS SC Mar 28-Apr 3
10-DAY DETAILED HOURLY WEATHER FORECASTS
VA Detailed Info:AWIS VA Mar 28-Apr 3
10-DAY DETAILED HOURLY WEATHER FORECASTS
TN detailed info: TN Mar 28-Apr 3
10-DAY DETAILED HOURLY WEATHER FORECASTS
| Chattanooga/Lov | Clarksville_TN | Crossville_AP | Dyersburg |
| Elizabethton_AP | Jackson_TN | Knoxville_AP | Memphis_AP |
| Millington | Nashville_Metro | Oak_Ridge_TN | Smyrna |
| Tri-City_RGNL_AP |
KY detailed info:AWIS KY Mar 28-Apr 3
10-DAY DETAILED HOURLY WEATHER FORECASTS
MD detailed info: AWIS MD Mar 28-Apr 3
10-DAY DETAILED HOURLY WEATHER FORECASTS
Good luck tonight!
Raleigh, NC 27695-7609
Sidney J. Harris, In: Reclaiming a Lost Heritage – Land-Grant & Other Higher Education Initiatives for the Twenty-first Century