Coptic Storms

[Dominic]

Every so often this topic comes up. The traditional Cypriot Weather Pattern. One listing I found sums it up:

The chart is fairly accurate within 2/3 days, most winds last between 2 and 6 days.

11 January Gale (very strong) Result: NA - NO
19 January Large Feeder Gale Result: NA - YES
28 January Gale Result: N/A - NO
18 February Small sun gale (very strong) Result: N/A - YES
10 March Equinox Gale (lasts about 6 days) Result: Yes storm on the 10th, plus heavy dust clouds on the 9th.
20 March Big Sun Gale (very strong) Result: NO.
25 March Wind Gale: NO
29 April Sand laden winds (hot and sunny) NO
27 September Cross-winds NO
21 October Crusade NO
28 November Broom Gale (very strong) NO
6 December Gale NO
20 December Small Gale YES

Now, it only ever seems to get mentioned when weather outlets predict bad weather. So it was last mentioned before the 11th Jan gales (which wasn't much), and has just been mentioned in time for the March 10th gale.

But what about the three dates in between?

I read a very good rebuttal to the whole coptic storm idea on another forum, but I thought it would be interesting if we actually applied a bit of science to it. So let's have a thread which highlights each date in the above list, and record what the weather actually did on that date.

[cyprusgrump]

* Awaits Devil *

[Mark]

The Devil is in the detail!

[PaphosAL]

I've got this saved somewhere on my ancient pc, using the original Arabic names, but cannot find the booger right now, doh...

Having spent a few Winter and Spring seasons in Pafos, I can verify the veracity of these annual weather prediction abberations!

[rambo]

Hi Paphos Al,
Would this be it?

11th of January El- kahira Gale (xxx)
19th of January El- fedara-El kebira Large feeder gale
28th of January un-named gale Gale
18th of February El-Shams -El Seghria Small sun gale( xxx)
10th of March El husson or El hasson (lasts double the usual time) Equinox Gale
20th of March El- Shams El kebina Big Sun gale (xxx)
25th of March Hawa Wind Gale
29th of April Khamseen winds (hot and sandy) Sand laden W. winds
27th of September El saleeb winds cross winds21st of October El Saleebish Crusade
28th of November El Mikness Broom gale (xxx)-very strong
6th of December Kassim gale
20th of December El fedra el Saggira(light gale) El small feedre gale.

Paul.

[Devil]

Coptic gales

Coptic gales are the legendary equivalent, in Cyprus, of the British St. Swithin's Day myth. There is absolutely no scientific evidence that a specific type of wind will blow on a given day. If it should happen, this is by pure chance, even though the gullible would say otherwise. If, as is more usual, it were not to happen, then the same persons may shrug their shoulders and say it is the exception that proves the rule.

Quoting a source, I read the following:

The Ancient Weather Lore of Arabia listed a series of gales, which occur regularly in the Eastern Mediterranean area. They generally set in from the South West & veer to the West * North West. The average duration is three days & their occurrence rarely deviates more than forty-eight hours from the dates shown below.

So, let's have a look at the so-called Coptic table:

2017-03-09_095010.png (21.92 KiB) Viewed 18281 times

* These gales are supposed to be exceptionally strong!

The above states that, for a gale to be "Coptic", it should start on the given date ±2 days, it should last three days, it should start in the SW quarter and it should be "gale", at least for all the winter ones (November to March). By definition, a near gale or a gale should blow with average wind speeds in the range 14 to 24 m/s.

Let's see what this means in a quotation which I wrote on a forum

The first date is 27/9. The 48 h tolerance in front, the 3 days duration and the 48 h tolerance behind means that if a gale blew on any date between 25/9 and 2/10, the gullible will cry, "There, I told you so!". However, that covers 7 days.

There are 13 dates in the list, so there are 91 days when, if there is a puff or two of air (from any direction), it could be a "Coptic" gale, out of a total of 214 days. That means that if a gale should blow, there is a 42.5% chance that it will blow on a "Coptic" day.

The first 2 or 3 and the last one are more isolated. Let's look at winter from the beginning of December to the end of March. There are 109 days between 6/12 and 25/3, i.e. 109 days and 9 "gales" or 63 potential gale-days. During that period, there is therefore a 57.8% chance that any wind will fall on a designated day, greater than 50-50. The Coptic believers cannot fail to be right over half the time, in terms of frequency.

However, there are two other criteria mentioned: direction and duration. Let's look at the last gale we had on 8-9/12. During the time it blew, it started from the N and veered to NE. Coptic gales are supposed to start from the SW, veering to NW. Therefore it could not have been a Coptic gale, could it? It lasted 2 days and not the 3 cited. Therefore it could not have been a Coptic gale, could it?

The next forecast wind from the right direction is on Friday 16/12, (this was written on 14 December) outside the Coptic days, but is a 4 m/s Beaufort "Gentle Breeze" by sailors' standards but respectable for us landlubbers and it will last only one day, at the most. It will have died down to 2 m/s by Saturday, veering to ENE.

I can't give scientific data for ±26/11 this year as my anemometer went on the blink (repaired now) but the windfarms produced no significant electricity between 24/11 and 1 December, so that the strong Broom Gale just did not happen.

My wind measurement for 19-26 October showed average wind speeds of 0.6, 0.9, 0.5, 0.5, 0.4, 0.4 and 0.3 m/s, respectively, hardly anything like a gale! The strongest average for October was 1.9 m/s on the 28th.

For the 27 September, the winds were even lower, averaging between 0.2 and 0.6 m/s for the 7 days in question.

Sorry to disillusion the believers but facts are facts.

Now, let's look at the current forecast

2017-03-09_095736.png (109.36 KiB) Viewed 18281 times

Friday looks as if it will have a moderate breeze from the 'right' quarter, but it will die down to almost nothing on Friday night.
Saturday will have a stronger breeze but it looks like backing away at first but it will continue overnight but SSE (non-Coptic quarter)
Sunday will continue with the wind from the S, veering into Monday

What will be really happening is that two fronts will come from the west and it is these that determine the weather, not the Copts!

[Crunchie]

I've always found them to be very accurate!

[Devil]

This thread duplicates viewtopic.php?f=3&t=963 where I have given the detailed view on the subject.

DOMINIC, can you please merge them?

[Dominic]

I have moved your post from that thread to this one, Devil.

I intend to keep this thread active for the duration of the experiment. The other thread will drift away and no doubt be replaced by another one when the law of coincidence decides, or not...

[Dominic]

But what about all the times when they aren't accurate? If you pick thirteen random dates in a year, and say that they will be stormy, especially if you weight them towards winter time, what would be the expected hit rate for random chance?

I'm adopting an open mind though, which is why I started this thread. I am keen to see what happens on the 20th and 25th of March too.

[PaphosAL]

I've been in Pafos late April on two or three occasions in the past. Amazed to wake up in the morning and opening the blinds, to witness an orange vista of mist. Spooky...

Outside, all the patios, furniture, windows, your cars were covered in a hard gritty red sand from the Sahara Desert in North Africa. Nightmare to clean off afterwards!!

It usually dumps this shite straight onto Cyprus in the NE weather swing in late April. Depending on the Jet Stream flow, it can also dump its deposits onto the UK, and even as far westwards as Canada, would you believe?

Cheers- AL

[Dominic]

Yes, but we've had a few dust days like that already this winter.

[Tankmanchris]

We experienced the Sahara dust dump even in Germany about 10 years ago.

As far as the Coptic Calendar is concerned, there may well be no scientific evidence to support but I find it fascinating how often the dates tie in with actual storms and gales, within a parameter of +/- 2 days.

[Dominic]

The weirdest weather I ever experienced was in Gran Canaria. There was a town where the wind blew constantly very strong. It never once stopped, and was always in the same direction. I remember standing on the beach leaning in to it. It was exceptionally warm, like standing in front of a giant hairdrier.

If the gates to Hell are anywhere on Earth, it must be near that place!

[Devil]

As far as the Coptic Calendar is concerned, there may well be no scientific evidence to support but I find it fascinating how often the dates tie in with actual storms and gales, within a parameter of +/- 2 days.

Take February of this year: 3 Coptic storms ±2 days = 15 days. What are the chances of any Feb. storm hitting one of them? 15/28 or 53.5%. As it happens, this year, the highest wind speed was 12.9 m/s on day 16, but cannot qualify as Coptic, as it was a North Wind. In fact, the only days that the wind was in the Coptic quarter (S-SW) were days 06, 22, 23 and 24 with a high of 5.1 m/s, in NOAA style reports.

[Dominic]

I saw some lightning over Polis way a while ago. But Polemi is standing firm at the moment.

[smudger]

Well it's crashing and banging and lighting up the sky here in Tremithousa.

My worst nightmare

[trevnhil]

And this side of Polemi did have it's fair share of Thunder and rain during the night..

Trev..

[Dominic]

Yes, I think I can put a tick besides the 10th March. Now on to the 20th...

[Devil]

We had a massive thunderstorm just after 02:00. Unfortunately, it brought down a load of muck that bunged up the rain gauge. Fortunately, I have a backup in the form of a funnel in a jam jar and this gives a fairly accurate estimation, so I've corrected the values on Weather Display, I think accurate to ±0.4 mm, near enough. Obviously, the timing on the graph is up the pole, but the values are good. At 10:30, the rainfall today is 30.2 mm, bringing the month to 40.4 mm and the year to 233.2 mm.

However, for the gale enthusiasts, from 19:20 yesterday evening to 01:14, there was not a breath of wind! Then there was a single gust of the almost negligible 1.5 m/s at 01:12. During the storm at 02:14, there was a single SSE gust of 10.8 m/s followed by a few smaller gusts up until the end of the storm. After that, there was no wind other than small gusts coincident with lesser rain storms until 09:47, when there was a gust of 3.1 m/s during a brief downpour. The current average (10 min) windspeed is 0.5 m/s ie next to nothing. So where are these Coptic Gales?

You can see the current graphs and data for yourselves at http://weather.bnellis.eu/current/trialindex.html. The chart is accurate (except for the rainfall correction timing) over the last 24 h. Note, you may need to press your browser Reload Current Page button to update it; you can see the displayed time in red under the green date near the bottom. Sorry that the page is experimental and incomplete, but the chart is OK.