Best source of Frost warnings

[Colin_M]

So what do you find is the best source of warnings about frost?

Having had my container spuds bitten by last Sunday's frost, I started looking at various forecasts. This week for Bristol on Thursday night:
- BBC weather reckoned it would be mild (it seems so)
- Metcheck reckoned it could get down to 1 or 2C

Anyone care to recommend somewhere that you find useful?

[Geoff]

I always use the Met Office but an evening bit of fresh air and a look at the sky is more reliable.

[Colin Miles]

A knowledge of local conditions, an outdoor thermometer plus a look at the sky. If temperature falling and clear skies then cover.

[Urban Fox]

I love

http://www.metcheck.com/V40/UK/HOBBIES/

They have a Hobbies section - which is great - because you want different weather forecasts if you are surfing, looking at the stars or down on the allotment.

The gardening section gives the usual Max and Min temps - but also SOIL temp... very handy when you're waiting to sow carrot seeds.

It also shows evaporation, humidity and rainfall. Brilliant

I has been a bit flakey in the past. But has been up and working well for a while now.

Christina

[Monika]

We use the BBC, metcheck and metoffice sites every evening and they often vary tremendously for our postcode. We are quite used to that because sometimes we get western England weather, sometimes eastern England weather - it all depends were the fronts are coming from. Metcheck tends to be the more accurate one but not always.

And, in a partial answer to your query, Colin, the frost the night before last wasn't forecast on any of them for our area but they did say it could go down to 2 degrees, so I covered everything up with fleece. Better safe than sorry.

[Johnboy]

I rely solely on my own assessments with frost. Because we get very late frosts here, up until the first week in June, most things are tucked up under fleece until then. Take potatoes for instance, our early potatoes are planted and fully earthed-up and are under heavy duty black polythene until there is a show of foliage and then they will be under heavy duty fleece and maybe a second layer of fleece.
Commercially potatoes hereabouts are not planted until mid April to the end of May and second early varieties are planted as Late varieties simply because of the frosts.
The other morning my weather station showed 37.5F half an hour before dawn but in that half an hour to dawn the temperature plummeted to 29.2F.
I know that Geoff is elevated about a 100ft higher than me and it would be interesting to hear if people living at higher elevation get the drastic swings in temperature that I seem to get here. Over my five acre plot there can be frost in one area and none in others and it is very difficult to predict.
JB.

[Colin Miles]

Urban Fox - use a soil thermometer. Far more reliable. Local conditions are always paramount and Metcheck and the Met only give expected conditions for a wide area. For frost they will be right most of the time, but there will always be one night when they aren't. I say night, but the temperature usually dips most in the hour before dawn, and sometimes afterwards.

[Colin_M]

Thanks to everyone for their comments.

I tend to agree with Monika that many of these sites quote information that can vary for any given day. But then a forecast is only an educated guess

Johnboy, when I looked out of the window at 7am today, it was cold but not frozen. By the time I went outside, the water droplets on my car had frozen solid and the grass down the allotment was sliver with frost. By luck, i'd brought our sensitive plants in last night! However my luck with this can't last!

[Colin_M]

To add insult to injury, I didn't check the forecast because it was still 12C in Bristol at 10pm last night (though clear & starry).

And this morning, the frost was glinting in the early sun. Looks like problem will go away by the weekend though

[Johnboy]

Hi Colin,
I appreciate that you live in the Bristol Area which is considerably warmer than I am stuck at 500ft in the hills of North Herefordshire but until at least the end April, even in your area, you should be protecting anything that you are growing and even more so things that are even the slightest tender.
Even when so called hardy things like Leeks and Brassicas were grown in nursery rows they were very prone to frost damage when young and in those days only cloches were used because fleece and polythene sheet had yet to be invented. I am growing some Leeks in a nursery row and some in modules to test if there really is such a difference to the actual finished Leek. The modules are growing on the bench in a tunnel and the nursery row in an outside bed with a fleece cloche. One small row is totally uncovered and although we have had some frost as yet they have not suffered but are less advanced to the fleece covered ones which are less advanced to the tunnel grown ones. If anything my observations are that the module ones are too advanced for the period and should not have been sown at the same time. BTW I have grown baby Leeks in modules on the bench and they grow very easily to around half an inch diameter in no time at all and are really tasty so if these go over the top for planting out you now know their fate.
We have frost right into the first week in June and Beans have to be grown with the second week in June as their optimum time which means not planting until first week in May.
I have a weather station which records temperature in 3 locations and the other morning the lowest temperature showing was 37.5F but my car windows, parked on the north side of the building, were covered in hard frost.
JB.

[Geoff]

Let's see how Met Office make out tonight - just off fleecing.

This Evening and Tonight:

Dry with long clear spells overnight for most, although some patchy cloudy drifting across the area. Becoming cold with light winds leading to a frost in some inland areas. Minimum temperature -2 °C.

[Geoff]

Quite a ground frost but weather station at 13' up made it -0.1°C at 06:00.

[Colin Miles]

Geoff - I believe the Met allow +/- 2C in their analysis of temperature correctness - max and min. So that means they got it right last night as far as your location is concerned.

Since the mean temperature range in Jan is around 5C and July around 9C you can perhaps see why their accuracy is so 'good'. But that's me being cynical.

[peter]

Given the number of variables involved in predicting the UK weather and, the size of the Met Office computers and the sheer complexity of the "model" used to do the calculations I am surprised that anyone expects a spot-on forecast for their quarter-acre.

From memory the Met Office had the UKs biggest and most powerful computer, its nearest competitors being GCHQ and Aldermaston - who starting from a design do virtual atomic bomb explosions.

[Colin Miles]

Peter - yes, any accuracy is remarkable, no matter what computer they use. But the better their perceived claims the more money they can claim in order to get bigger and better computers. I did a months comparison in June 2010 comparing forecast temperatures with actual and the mean CET values +/- 2 C. I seem to remember that there was a 9% improvement in the Met forecasts compared with that taking the mean values +/- 2C (84% cf 75%).