Multi-State Freeze and Frost Update (10:45am, Sat., March 11, 2017)
go.ncsu.edu/readext?453330
“Daylight Savings Time Starts Tomorrow”
Hello again!
I was feeling a little guilty the day before yesterday in advising an Eastern NC strawberry grower to proceed ahead with a large row cover investment. As you may recall, there was a significant change in the forecast for NC that happened early Friday morning (for the better), and with the new forecast with minimum temps over the next week of 27 F and higher, you could make an argument that the covers would not be needed (for this particular 10 day period from today until March 20). In Table 1 (below), I noted that you could use row cover OR sprinkling on all of the events. In Table 2 you can see how in this morning’s forecast how things have changed (again). And, please note that on Tue/Wed, March 14-15, we are no longer looking at a minimum air temp of 31, but now 22 F. Wow! That changes everything! With a temperature that low, and sustained winds of 9 mph we are dealing with a very dangerous frost/freeze (you say, “What is a Frost/freeze? Check out: cold protection in winegrapes …the short version is that it is cold event with sub-freezing temps and winds in the range of 5-9 mph; if winds were 10 mph, it would be a windborne freeze). You can argue that sprinkler irrigation alone can handle a “frost/freeze,” but I would not risk it – there is real risk of evaporative cooling damage even when winds are above 7 mph. The best solution to keeping open blossoms safe is to run water on top of covers.
Fig. 1. This is the best solution for a frost/freeze, or windborne freeze.
Without the purchase of these new covers, the grower would have been forced to rely on sprinkling alone, and that is a VERY DANGEROUS PROPOSITION WITH SUSTAINED WINDS OF 9 MPH.
Table 1. Kenasville AWIS Hourly (3/10/17)
| Kenansville | Morning sky cover | Min air temp (F) | Time of minimum | DP 6 a.m. (F) | Winds 6 a.m. (mph) | Frost potential | Strategy | |
| Fri/Sat | Few clouds | 34 | 7:00 a.m. | 24 | 3 | ? | Row cover or H20 | |
| Sat/Sun | Overcast | 32 | 10:00 p.m. | 29 | 5 | Frost 10 p.m. | Row cover or H20 | |
| Sun/Mon | Scattered | 30 | 5:00 a.m. | 29 | 11 | Frost midnight | Row cover or H20 | |
| Mon/Tue | Overcast | 42 | 5:00 a.m. | 40 | 9 | NONE | ||
| Tue/Wed | Broken | 31 | 6:00 a.m. | 22 | 14 | Unlikely | ||
| Wed/Thur | Clear | 27 | 5:00 a.m. | 21 | 7 | Frost at 6 a.m. | row cover or H20 | |
| Thur/Fri | Clear | 35 | 6:00 a.m. | 33 | 5 | Frost at 2 a.m. | row cover or H20 | |
Table 2. Kenasville AWIS Hourly (3/11/17)
| Kenansville | Morning sky cover | Min air temp (F) | Time of minimum | DP 6 a.m. (F) | Winds 6 a.m. (mph) | Frost potential | Strategy | |
| Fri/Sat | Scattered | 32 | 7:00 a.m. | 22 | 2 | ? | need to ask | |
| Sat/Sun | Overcast | 31 | 7:00 a.m. | 25 | 6 | ? | Row cover or H20 | |
| Sun/Mon | Clear | 30 | 4:00 a.m. | 28 | 5 | Frost midnight | Row cover or H20 | |
| Mon/Tue | Overcast | 40 | 5:00 a.m. | 37 | 9 | NONE | ||
| Tue/Wed | CLEAR | 28 | 5:00 a.m. | 21 | 14 | Windborne Freeze | Row cover only | |
| Wed/Thur | CLEAR | 22 | 5:00 a.m. | 14 | 9 | Frost/freeze | Row cover + H20 | |
| Thur/Fri | CLEAR | 28 | 5:00 a.m. | 25 | 3 | FROST 2 a.m. | row cover or H20 | |
| Fri/Sat | Scattered | 40 | 5:00 a.m. | 36 | 9 | NONE | ||
ARE YOU TAKING ADVANTAGE OF THE AWIS HOURLY FORECAST TOOL? (I can stop producing it if it is not useful?)
<GROWER FEEDBACK ON WHETHER TO CONTINUE PUBLISHING AWIS HOURLY PRODUCT>
- Yes, Barclay, the AWIS hourly forecast is very useful.
We look at forecasts from AWIS, AccuWeather, and Weather Channel (came on my smartphone). We prepare for the “worst” forecast and hope for the “best.”
We did not renew SkyBit this year. It was never that accurate for our farm(s). Too many times, as related to frost, if we had waited for the SkyBit frost time, we would have missed the start of the frost, sometimes badly. We do better looking at temps, dew points, winds, and cloud cover, all from AWIS, AW and WC, to come up with our own “frost” forecast. That and “looking at the donkey.” - <Editor’s comment: My philosophy on this whole subject is that the more quality weather information you can access ahead of a cold event, the more successful you will be in managing the event when it arrives. Skybit does one thing very well — it is unique for being able to give you strawberry canopy-level, minimum temperature information, 2-3 days AHEAD of the event. And, then it continues to give you information about those canopy minimums right up until the late afternoon/early evening prior to the cold event. Having this information on what the actual canopy minimum air temperature can be is very useful in making ADVANCE preparations to protect your crop. SkyBit does not include a FROST forecast – accurate forecasts of when a (white) frost will occur are very difficult to make. As far as knowing when to initiate protective measures against a white frost situation with sprinkling, I agree with Tom about the importance of “looking at the donkey” (i.e. watching for evidence of ice crystals forming on solid objects at the crop level). But, for a potential black frost scenario, you need advance information on canopy minimums, and that is something that SkyBit excels at providing.>
(cont’d) - Thankfully, 26 on Wednesday night (subject to change, of course!) looks to be our worst for this cold event. Our covers should do us fine. The biggest problem is our bees can’t work covered strawberries, but with these cold temps the bees don’t work much anyway. Plus the plants are rather “arrested” so blossoms aren’t popping out and getting past pollinating, either. Actually, I wonder if the wind-caused “flapping” of the covers (really more like rolling ocean waves than “flapping”) isn’t sufficient to shake some pollen around and get that job done? I’d like to hear your take on that.
Thanks for the advisories. It’s interesting to know what others are dealing with, too.
Tom Baker - Feedback from SC Growers:
-
Dr. Poling,
North Augusta TODAY. Yes the advisory is helpful. We integrate 4 to decide on our strategies. Yesterday we hit 80F, could not harvest or cover for lack of labor and had to overhead protect 0500-0745 despite forecasts of 40F this morning. You SNOOZE, you LOSE!! Today we are harvesting & selling hundreds & covering. Looks like a CHALLENGING week ahead, probably requiring combination protection and PRAYERS! I’ll send some pictures later today, as the fruit is BEAUTIFUL!!
Sincerely,
Clyde - Eric Hunter- Yes, absolutely use and appreciate the AWIS tool. I think its one of the more valuable tools we have. Coupled with Skybit makes it a must have in times like these in my opinion.
Looking ahead, my guess last week that we would hit the 18-19 next week mark appears to be coming true. Are you of the opinion that double covers of 1.25oz and 1.50oz are adequate for protecting the blooms without overhead irrigation?
- Reply – I feel the row cover (single cover) + sprinkling is more reliable for upper teens than double covers. I wish we had more data on this, but we actually had a presentation at the VA Beach meeting where a grower from Kentucky indicated to us that he felt the row cover + sprinkling is better than double covering.
AWIS is covering 71 locations in NC Alone:
I personally “hope” that many of you are taking advantage of the AWIS Hourly Forecast tool that is being provided as a service to the strawberry industry this season. It can really help you make sense of what could be happening with the weather in you farm location on an hour by hour basis for the next 10 days. One trick to using the AWIS Hourly Forecast is to select the city/town in NC that is closest to your farm. They are now covering 71 locations across the state of NC.
Create an excel spreadsheet to track changes:
Regarding the AWIS Hourly Forecast tool, I find it helpful to also create an excel spreadsheet summarizing the basic weather information derived from this forecast (that is what I just did for Tables 1 and 2), and if you click on Kenansville (below), you can see all the data that went into Table 2 this morning. AWIS updated this forecast at 8:47 a.m. this morning. What I try to do each morning (time permitting), is review the previous day’s excel spreadsheet against the new forecast for a site that I like to follow closely (like Kenansville, NC; Farmville, VA and Chesapeake, VA). And, when you come across a significant change in the weather forecast, as I did this morning for Kenansville (the new minimum of 22 on Wed/Thur), you can then make the appropriate adjustment in your Crop Protection Strategy (3rd C). If I were still teaching at NCSU (I retired in Dec 2010), I would have my students become familiar with tracking “strawberry weather during bloom” for their home location (using AWIS hourly information), and then have them make a decision on the best Strawberry Crop Protection strategy based on the changes they are seeing in the AWIS data from day to day. Recording this data on a regular basis, and then reviewing it, can be a terrific learning tool for students and growers!
AWIS HOURLY FORECAST FOR MD, VA, NC, SC, GA and KY
Before I list all the AWIS Hourly Forecasts for MD, VA, NC, SC, GA and KY, I am also going to share the AWIS Frost/freeze forecast for tonight for the benefit of NC growers – I only wish AWIS produced these for the other states as well. What NC growers may notice tonight’s AWIS Frost/freeze forecast is the mention of little if any frost due to clouds in some areas of the state. This can be a tricky situation! All the temperature numbers for air temp and dew points are right for frost, and with long periods of calm, and just scattered clouds, it could happen!
Tonight's AWIS Frost/Freeze Forecast for NC
AWIS Weather Services, Inc. North Carolina Frost/Freeze Forecast Produced at 504 a.m. CST on Sat Mar 11 2017 ... Forecast for Tonight ... Northeast NC Coast Currituck/Camden/Pasquotank/Tyrrell Counties **** FREEZE COLD LOCATIONS **** **** LITTLE/NO FROST DUE TO DRY AIR **** Lowest Temperatures: 29 - 36 Elizabeth_City Min 29 Durations at/below 32: 0 - 8 Range Dewpoint Temps: 10 - 30 Range Wetbulb Temps: 25 - 37 AVG Wind Direction/Speed: N 5 Long Periods of Calm AVG Sky Condition: Mostly Cloudy 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) 03/13/17 03/14/17 03/15/17 03/16/17 03/17/17 03/18/17 -------- -------- -------- -------- -------- -------- 31 - 37 40 - 46 32 - 38 29 - 35 36 - 42 41 - 47 -------- East Central/SE NC Coast Carteret/Pamlico Counties **** FREEZE COLD LOCATIONS **** **** LITTLE/NO FROST DUE TO DRY AIR **** Lowest Temperatures: 32 - 35 Morehead_City Min 35 Durations at/below 32: 0 - 1 Range Dewpoint Temps: 17 - 32 Range Wetbulb Temps: 27 - 37 AVG Wind Direction/Speed: N 3 Long Periods of Calm AVG Sky Condition: Mostly Cloudy 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) 03/13/17 03/14/17 03/15/17 03/16/17 03/17/17 03/18/17 -------- -------- -------- -------- -------- -------- 31 - 35 43 - 48 31 - 33 24 - 29 30 - 34 44 - 45 -------- Southeast NC NWS FORECAST ZONES 87-90,96-101 **** FREEZE COLD LOCATIONS **** **** LITTLE IF ANY FROST DUE TO CLOUDS **** Lowest Temperatures: 32 - 36 Elizabethtown Min 35 Durations at/below 32: 0 - 1 Range Dewpoint Temps: 15 - 33 Range Wetbulb Temps: 32 - 40 AVG Wind Direction/Speed: NE 4 Long Periods of Calm AVG Sky Condition: Cloudy 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) 03/13/17 03/14/17 03/15/17 03/16/17 03/17/17 03/18/17 -------- -------- -------- -------- -------- -------- 29 - 35 34 - 43 27 - 33 21 - 28 26 - 33 42 - 46 -------- North-Central NC Franklin County Area **** FREEZING TEMPERATURES **** **** LITTLE IF ANY FROST DUE TO CLOUDS **** Lowest Temperatures: 26 - 33 Louisburg Min 26 Durations at/below 32: 0 - 9 Durations at/below 28: 0 - 4 Range Dewpoint Temps: 7 - 19 Range Wetbulb Temps: 24 - 34 AVG Wind Direction/Speed: NE 4 Long Periods of Calm AVG Sky Condition: Cloudy 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) 03/13/17 03/14/17 03/15/17 03/16/17 03/17/17 03/18/17 -------- -------- -------- -------- -------- -------- 24 - 31 31 - 40 21 - 31 18 - 28 25 - 35 36 - 42 -------- North/Central NC Alamance County Area **** FREEZING TEMPERATURES **** **** LITTLE IF ANY FROST DUE TO CLOUDS **** Lowest Temperatures: 27 - 33 Graham_AG Min 30 Durations at/below 32: 0 - 8 Durations at/below 28: 0 - 3 Range Dewpoint Temps: 8 - 19 Range Wetbulb Temps: 26 - 34 AVG Wind Direction/Speed: NE 5 Long Periods of Calm AVG Sky Condition: Cloudy 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) 03/13/17 03/14/17 03/15/17 03/16/17 03/17/17 03/18/17 -------- -------- -------- -------- -------- -------- 25 - 30 32 - 37 21 - 27 19 - 24 25 - 31 37 - 42 -------- South/Central NC Richmond County Area **** FREEZE COLD LOCATIONS **** **** LITTLE IF ANY FROST DUE TO CLOUDS **** Lowest Temperatures: 31 - 34 Ellerbe Min 34 Durations at/below 32: 0 - 2 Range Dewpoint Temps: 13 - 31 Range Wetbulb Temps: 29 - 37 AVG Wind Direction/Speed: NE 7 AVG Sky Condition: Cloudy 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) 03/13/17 03/14/17 03/15/17 03/16/17 03/17/17 03/18/17 -------- -------- -------- -------- -------- -------- 28 - 33 32 - 40 25 - 29 23 - 27 29 - 32 39 - 44 -------- Interior/EC-SE NC Wayne County Area **** FREEZING TEMPERATURES **** **** LITTLE IF ANY FROST DUE TO CLOUDS **** Lowest Temperatures: 30 - 34 Goldsboro_AG Min 33 Durations at/below 32: 0 - 4 Range Dewpoint Temps: 17 - 30 Range Wetbulb Temps: 30 - 35 AVG Wind Direction/Speed: NE 3 Long Periods of Calm AVG Sky Condition: Cloudy 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) 03/13/17 03/14/17 03/15/17 03/16/17 03/17/17 03/18/17 -------- -------- -------- -------- -------- -------- 29 - 32 38 - 42 27 - 31 24 - 26 29 - 31 40 - 46 -------- For more detailed information visit www.awis.com or call 888-798-9955. Copyright 2017 AWIS Weather Services, Inc. All rights reserved.
Multi-state Update on Saturday, March 11th:
Note: I will not be able to produce an advisory of this sort until next weekend, so plan on referring back to this Saturday advisory to obtain current AWIS Hourly Information – these links for individual towns and cities remain updated. I try to do this as a service to the industry, and given the extreme toughness of this season so far, I am glad that I jumped in to help out some. But, I also need to attend to a number of personal things in the week ahead. Of course, the Sunday Outlook will be published tomorrow evening.
MD MD Outlook
10-DAY DETAILED HOURLY WEATHER FORECASTS
Fig. 2. It was nice to take a break from all the ADVISORY WORK yesterday morning (Friday) to visit strawberry growers near our townhome in Williamsburg. Many of you may recognize Roy Flanagan in the photo – Roy is our VA Extension Agent out of VA Beach. Roy was also recipient of the Outstanding Industry Service Award of the NC Strawberry Assn. last Nov. He also hosted an outstanding Mid-Atlantic Strawberry Meeting in VA Beach at the end of February.
VA VA Outlook
10-DAY DETAILED HOURLY WEATHER FORECASTS
NC NC Outlook
10-DAY DETAILED HOURLY WEATHER FORECASTS
SC SC Outlook
10-DAY DETAILED HOURLY WEATHER FORECASTS
GA GA Outlook
10-DAY DETAILED HOURLY WEATHER FORECASTS
KY KY Outlook
10-DAY DETAILED HOURLY WEATHER FORECASTS
Question on botrytis (9:45 a.m. Sat)
Eric Hunter asked me, “Over the next few days it’s gonna be wet and cool. We’d like to go ahead and spray, but my question is with it being so cool, is a botrytis spray necessary? Seems like I remember cooler temperatures not being conducive to the spread of botrytis?
Dr. Guido Schnabel, Clemson:
If temps are below 40 there is little chance of infection. But if people use row covers and don’t get them off as soon as temps rise there will be problems.
Added info. Strawberry Disease Compendium:
The ideal temperature for sporulation is 59-72 F, and optimum at 64 F. So, I would have a look at AWIS hourly temp information for your area, and depending on sky conditions, you might be getting some very significant elevation of temperatures under the row covers!
In closing, I want to wish everyone best of luck this weekend and week ahead. Given all this cold weather headed our way again this week, I think I’d rather be back in warm-sunny Florida working with my new friend Rono in our advanced selection breeding plots!
Barclay
Fig. 3. An advanced strawberry selection – maybe we’ve gone a little too far with better berry size objective? This particular berry had a weight of 120 grams (4 1/4 ounces), and measured 10 cm (4 inches) in width.
Fig. 3. An advanced strawberry selection – maybe we’ve gone a little too far with better berry size objective? This particular berry had a weight of 120 grams (4 1/4 ounces), and measured 10 cm (4 inches) in width.
Example SkyBit: