Frost more likely in sheltered spots?

[rary]

I have this thermometer with a sensor on the end of a cable which I hang out of the window so I can see the temperate on the digital readout.
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That may be the answer to a problem I have. If it is cold/frosty it is usually my turn to go and make the morning cup of tea.....there must be sensors hidden in the bedroom

How is it that the national weather forecast, the local weather forecast and the Ceefax weather forecast are all saying something different, though the information all comes from the same source (the Weather Centre)? One of life's mysteries!

There is a better chance for one of them to be correct

[Kristen]

I don't think there is any chance of frost at this time of year where I am.
It is close to the centre of Nottingham

...

It is a long long time since there has been a frost, probably February I'd say.

I am 99% certain I have seen the last of the frost this year.

According to Wudnerground there was a frost in central Notting on 3rd of May last year - probably one of the mildest winters on record

We can get a late frost in any year. The milder the spring the more advanced the plants and the greater the devastation a late frost causes.

The only solution is to be prepared - keep an eye on forecasts and be able to bring plants in, or cover with fleece, etc. - although I remember a frost of -6C in late May, several years ago, and fleece (alone) was no use for that.

There's a brilliant little gadget you can get that looks like a usb stick ... Only costs about £5 - £10

I've got some USB sticks but have never found them at a price close to that. If you had a link I'd appreciate it, thanks

[esbo]

The temperature can vary quite drastically over a very small area. In an average sized garden for instance, the lowest overnight temperature can vary as much as 6 or 7 degrees.

If you measure the ground temperature, it could be 0 and yet measure the temperature 3ft above ground and it could be 4 or 5 degrees. Therefore if you have a sensor that you stick out of a window, say 5ft above ground level (and obviously sheltered by the house) the temperature in the same garden could be 7 degrees or even more.

Ground frost is the main danger at this time of year, not frost in the air.

I guess it might be an idea to put pots out above ground level, provided they do not get blown away!
It might give them and extra degree or so of heat?

Actually this thermometer I has does have a frost alarm on it, problem is I would not be there to hear it!

Now if I could get it to give me a phone call........

[skeggijon]

I've got some USB sticks but have never found them at a price close to that. If you had a link I'd appreciate it, thanks

Loads of them in that price range on fleabay

[Kristen]

Thanks. I should have checked there first!

The ones I have are Lascar (or similar). eBay has those (UK supplier) for £35, which is about the price I have found such things in the UK.

The cheaper ones [on eBay] are all China / Hong Kong supplied. I'm not anti, but they don't look to be the lease bit splash-proof, and I expect there is a risk of Import Duty (unless Mr Customs Man busy / looking the other way when the package arrives )

Be interested to hear what folk think of any Chinese-import USB temperature sticks they might have. (I noted that there were some disposable ones on eBay too - amazing! - would be great for something temperature sensitive being sent through the post, or similar ...)

[skeggijon]

i've got 1 too, but tried the china 1's and whilst they're not the same quality of course, they do the job and no issues with customs, because value is less than £20

[Potstubsdustbins]

I import a fair few items from abroad LED's for instance and touch wood have never had a problem.

[esbo]

Just had a look at my forecast and I have an over night low of 1C on the 26th

I will manage though, they will come back inside if things look dodgy

I will put some out on Friday when it is 10C, then 8C then 3C.

Might bring em in for the 3C.

I will be OK it will only be a couple of bean plants that might be a problem really.

edit - previous wrongly said 29th instead of 26th

[Potstubsdustbins]

I obviously have the same forecast and binned the last of my fleece today, very tatty. I will buy more tomorrow just in case they get it right for a change.

With a bit of luck the fact I am going to spend money will mean it won't happen.

[Penellype]

Every run of the models looks chillier here - from Sunday through to the end of the forecast period (Friday next week) we have only 1 night forecast to be as warm as 2 degrees

[esbo]

There is has been an upgrade in the forecast for me from 1C to 2C on the 26th.


edit - previous wrongly said 29th instead of 26th

[Penellype]

The cold period does look to be getting shorter, but there is still huge uncertainty. This is the latest run of the GFS model (12 noon today) - 850hps is about 5,000 ft up in the atmosphere, so ground level temperatures are warmer than this:

(taken from wetterzentrale.de)

This shows the predicted temperatures at this height from 20 different runs of the model starting from very slightly different conditions (within experimental error of the measurements). The white line is the average of the 20 runs. You can see that the lines start to diverge as early as 26th April, and by the time it gets to the cold dip on 27th there is a 7 or 8 degree discrepancy between the warmest and coldest runs. As a general rule the -5 line indicates the possibility of wintery conditions (sleet/snow) if other factors are favourable, and the -10 line is the sort of place you would expect to see the lines in a cold snap in January, so those blue lines are very cold indeed. The scatter by 1st May is bordering on absurd.

The thick green line is the "operational" run, which the weather forecasts tend to be based on, so if you go to a weather website such as windfinder.com which uses the GFS model, that is what you are looking at. This line has been wagging up and down like the tail of a dog recently - the 6z (6am) run had it below the red seasonal average line for the whole of the graph after 27th, and now its up and down a lot. The midnight run had it above the red line from 1st May to the end of the graph...

In other words, nobody has the faintest idea what is going to happen after the temperature drops on Sunday.

[esbo]

Yes this is the problem with weather forecasting, the further ahead you look the more likely it is to be wrong, as I say in just one day the temp for the 26th has gone up one degree, so who knows what it will be on the 29th.

[edit] It seems I said 29 instead of 26th, however the temp is now back down to the original 1C.

I don't think I misread it because the 29th says 5C.

I may put my 2 biggest plants outside to night, for face temps of 7C 11C then 6C before bringing them back in for the 1C. The next two nights as 3C, a little chilly so I am as yet undecided about them.

I may see if I can rig my thermometer to record ground level temp, I just remembered you can see it to record the and remember the lowest temperature, which is handy, the only problem there is setting it up to do that, which might be tricky (even if I manage to find the instruction lol).

But it is a very useful tool if you know how to use it, I got it from Aldi for £5, money well spent, I love being able to see the actual temp outside so easily.

[Martin H]

Here. Metcheck is still predicting zero C before dawn on Monday morning.

[Potstubsdustbins]

Well my new toy, temperature data logger has arrived, all I have to do now is learn how to set it up.

I may be gone sometime.