Many moons ago

A flash of light …

Many moon's ago, I posted my first reply to the newsgroup. It was an addled misconception that I had, concerning the regional way that tides behave.

Someone had asked why, after a small snow shower, some roads and gardens would be covered and others near-by were not.

In Britain, a tidal pulse moves around the coast like a three phase induction. Dover and Liverpool and somewhere in Orkney have an high tide. At the same time, Bristol Hull and somewhere off Cork in Ireland, have a low tide.

Tidal tables are based on the above ports. What you do is add or subtract the time of high or low water for your location. (In another table, given in the appendix.)

Tide tables are little booklets you can put in your shirt pocket, designed for occasional reference if you go out in a small boat. They are just printings of the tidal charts for the nearest large port.

The sort of thing you might have on you in a pub, when a friend asks you to set up a fishing expedition.
The one I used in my youth was Laver's Liverpool tide tables.

Abergele was 20 minutes earlier (or was it later?) than Liverpool. And Bangor, at the mouth of the Menai Straight, was (IIRC) 2 hours and 28 minutes earlier(?)

Years later, after moving to Abergele, I spent a lot of time on the beach wondering about the odd behaviour of the weather in that bay.

It seemed connected to the tides somehow. But it just wouldn't run true with the tables or the weather forecasts. Time and again I'd be out in an hailstorm wondering at the occurrence at high or low water.

And then the next time, nothing!

Then there was the way the waves left the sand. Sometimes it piled it up on one end of the beach and left it there unmolested until another high water a few weeks later would move it all back out.

And every tide, the pebbles in the sand would be left in inverted arches of perfect geometry. And with another period, there would be just plain sand or no distinguishable pattern of sand and pebbles.

It was very frustrating and also very engaging.
It was like being married.
To someone you loved.

I forget what the consensus of opinion was with my first Usenet post. (Heat Islands in towns I think.)

I couldn't refrain from adding my two ha'pence that it was a tidal effect.


12 thoughts on “Many moons ago

  1. 10 hPa is now approaching all time high temperature! Even 100 hPa level is now above the mean zone. Zonal wind at 150 hPa showing a rapid decrease now To which someone replied:Shame these data can't be plotted alongside one another: I'd like tosee:a) What percentile the 10hPa temperature is atb) What percentile the 100hPa temperature is at similarlyc) what percentile the 150hPa wind is at through time to see any evidence of downward propagation. I added:I'd like to see the upper level plotted against lunar phases. The upsand downs seem incredibly weekly events. Speaking of which:Feb 7 21:54 Feb 14 17:04 = two anticyclonic events, preceded by one of these:Jan 31 04:10 which, IIRC, is the same as one of these:Nov 10 20:16 but with a Greenland High.> wouldn't take much to do would it?Print it out on graph paper or something?

  2. I've been trying to find an alternative PDF editor on y system. The other Linux OSs all had a reader that you could use to clip text and images from.The bog-standard on this thing is hopeless.Anyway, what I wanted was to reproduce the three charts in the above links and show what they meant.

  3. And finally:On calm and clear winter nights here, the air temperature fall is invariablyinterrupted by a slight rise towards midnight before falling away again inthe small hours with a Temperature minimum just after sunrise.I've always put this down to katabatic flows into the adjacent valley pulling less cold air in from the ridge to the east before everything generally cools down later in the night.Variations in wind speed will also be a factor.Although the AWS data plot allows this to be studied at leisure I recall noticing this way back in the 1960's using traditional instruments.The setting was a back garden with a railway embankment beyondand a general slope eastwards.The other temperature variation pattern I've noticed is associated with cloudy drizzly winter easterlies.Little variation in temperature between day and night but with a slighttemporary warming in the evenings.Phillip Eden suggested that this was due to less cold 'afternoon air'blowing westwards from the continent aand passing through.Still, we don't get winter easterlies any more, northerlies are the new easterlies.

  4. Anticyclone activity is harnessed in the upper atmosphere, sometimes, producing a synegetic affect. In winter it makes things extra cold, in summer extra warm.When a tropical storm is growing, if the upper atmosphere is like the above and near enough. It will act like a suction pump to add powr to the vortex below.The combination is deadly and can drive a tropical depression through all the categories into a Cat 5 cyclone, the highest known.Any ships caught in it will suffer badly. Old ships with fake inspection records will be sent to the bottom of the sea with all hands lost: new tankers with sound structures will be badly damaged if it gets hit by a "Rogue Wave":

  5. Finally:1. Phil Layton 2. Scott W 3. Freddie4. Dave Cornwell5. Roger Smith6. Paul Hyett7. Tudor Hughes 8. Graham P Davis 9. George Booth Is the Farnborough data as strikingly diurnal as Phil Layton's?I think Freddie has just explained the anomalous behaviour of micro-climates (weather in small geographical locations) and my first post to this newsgroup, why snow occasionally covers some places and not others, in the same region.I think this deserves a paper. Well done all.

  6. Same thread:___I have had a similar 'problem' for weeks on my station – I did have suspicions that dampness in the cables was to blame – now I'm not so sure as others have reported this… ___I think it is due to the fact that the air isn't still, and there is some mixing going on of the slightly warmer air found tens of feet above the ground.  I quite often experience it with my weather station.  I think it is much rarer to get a completely still night than it is to experience a night with one or two knots of breeze to mix things up.

  7. Wasted on experts was myattempt to draw them out further:I don't know how useful the scientific explanations are but the fact that such stuff occurs as often as not with the incidence of such series as the following types, aught to mean something to a group aimed at understanding the way a planet is tuned: 5.1 M. NORTH OF ASCENSION ISLAND  5.1 M. SOUTH SANDWICH ISLANDS REGION<  5.1 M. SOUTH SANDWICH ISLANDS REGION<  5.3 M. MOLUCCA SEA  5.2 M. SULAWESI, INDONESIA  5.6 M. SOUTH SHETLAND ISLANDS  5.1 M. SOUTHERN MID-ATLANTIC RIDGE  5.1 M. SOUTH SHETLAND ISLANDS<  6.2 M. SOUTH SHETLAND ISLANDS<  6.6 M. SOUTH SHETLAND ISLANDS<  5.7 M. BABUYAN ISLANDS REGION, PHILIPPINES  5.0 M. SOUTH SANDWICH ISLANDS REGION  5.2 M. TONGA REGION  5.0 M. HINDU KUSH REGION, AFGHANISTAN  5.1 M. SOUTH OF THE KERMADEC ISLANDS<  5.1 M. SIMEULUE, INDONESIA (stretching, I know)  5.1 M. SOUTH OF THE KERMADEC ISLANDS<  5.2 M. SOUTH SANDWICH ISLANDS REGION<  5.1 M. SOUTH SANDWICH ISLANDS REGION< That and the fact they (multiple, similar magnitude earthquakes and multiple (not only occluded) fronts) are heading across an ocean to us as though we were being fed by its peristaltic action on something meteorology is too immature to swallow. Though, god knows, we aught to ready for it by now! I was actually coming here to ask if it was common for the cloudless skies of this spell to produce such warmth when last spell I was freezing. And, as usual, I find the riddle already set, with losers speculating and making the pieces fit and all the rest of it.

  8. Others came up with similar explainations for the upper air winds on a winldess night:This kind of variation is normal here with a weakish synoptic gradient between S and E and a clear sky.  With any other wind direction, eg NW, the variations are much smaller and often non- existent. My own explanation is that on a clear night cooling over the gentle dip-slope of the North Downs can produce low temperatures early in the evening but the general geostrophic wind occasionally disturbs the inversion, sometimes more than once during the night.It is noticeable from the thermograph traces, that such rises are almost always confined to the period before about 0100Z, even in the summer. My guess is that at the crest of the North Downs (Botley Hill, 877 ft, 4 mi SSE of here) such variations are much less.There is also the possibility that with a very weak gradient there is akatabatic effect, the dip-slope having a typical gradient of about 1 in 50.___First became aware of the same thing nearly fifty years ago at RAE Bedford.It was more obvious what was happening because temperature dropped sharply when fog was advected up to the airfield from a nearby cold hollow and jumped back up when it drained away.We'd had a snowfall in the morning and by 11Z the sky cleared, temperaturedropped to -2C and ground fog formed. In the afternoon, temperature wasjumping around between about -3 and -6C but was -10C at 18Z.I think F/C overnight min [forecast minimum temperatures] for us,issued by 3-group in the afternoon, was -3C!Also saw the same when I was at Wattisham, with varying temperaturesdue to wind, or lack thereof.Temperatures might be a good 5C above surrounding area when we pokedabove the inversion.Visibilities were also affected;we jumped to 40Km one night when everywhere else was below 3Km.Stuffed my TAFs [forecasts for air-fields] good and proper!

  9. wondered if anyone else has had temp rises and falls during the last couple of nights. Last night it was -1.6c at 21Z then 0.9c at 02Z this morning, then -3.8c at 07z Tonight it was -1.4c at 17z and back up to 2.1c at 20z, now back down to -1.1c now (22Z) Don't think there was/is any cloud to explain it… I see Gatwick METARs show : EGKK 160350Z 07006KT 4000 HZ NSC M04/M04 Q1023 EGKK 160320Z 07004KT 4000 BR NSC M03/M03 Q1023 EGKK 160250Z 09005KT 6000 NSC M03/M03 Q1023 EGKK 160220Z 07003KT 7000 NSC M02/M02 Q1023 EGKK 160150Z 07004KT 5000 HZ NSC M02/M03 Q1023 EGKK 160120Z 08003KT 6000 NSC M03/M03 Q1023 EGKK 160050Z 09004KT 6000 NSC M03/M04 Q1023 EGKK 160020Z 08006KT 7000 NSC M04/M04 Q1023 so something similar is going on there…

  10. The original poster replied to this with an image:Thanks Freddie – backed up by the wind graph.. agreed:Yes – it's happened here a lot this week. One was definitely passing cloud but I think the others were slight variations in wind. ___Looking at the Farnborough data – the variations here are just as striking – it does seem that the wind is a major factor.  Here in particular a N or E drift will bring rather warmer air from the built-up area across the runway towards the weather station.___>Thanks Freddie – backed up by the wind graph.. > Never thought to correlate wind speed & nocturnal temperature fluctuations on my records… ___Nor me especially.  They tie up perfectly with last night's rise in temperature between 22.00 and midnight and increase in wind speed.

  11. One image I did get clearly shows a strong relationship to the warmth experienced on hot summer days in Britain: With just one picture to go on though…

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