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#1005249 - 09/08/2011 20:53 Clouds on the horizon over the sea
Ms Milo Offline
Weather Freak

Registered: 17/03/2010
Posts: 355
Loc: Angourie, North Coast NSW
This is a question my mate asked and I thought I'd put it to the forum:
Why is there clouds on the horizon over the ocean every morning before sunrise even on perfectly cloudless days? Has been every morning for about 8 weeks. They disappear over the horizon after sunrise.
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#1005335 - 10/08/2011 15:17 Re: Clouds on the horizon over the sea [Re: Ms Milo]
SBT Offline
Meteorological Motor Mouth

Registered: 07/02/2007
Posts: 14286
Loc: Townsville Dry Tropics
It could be a number of elements Ms Milo. Firstly the air is reasonably clear first thing in the morning and the clouds you can see could be quite a long way away. Maybe as much as 120klm as you are only viewing the tops. As the air density appears to change (actually it is just the suns rays refracting at a different angle) the clouds can dissapear as the visibility range decrease. Just my theory.
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#1005337 - 10/08/2011 15:25 Re: Clouds on the horizon over the sea [Re: SBT]
ant Offline
Meteorological Motor Mouth

Registered: 05/10/2002
Posts: 9063
Loc: Overlooking ACT at 848m
Yes, they might be camped out in a spot way out to sea, and they disappear as the earth rotates?

I live on a highish mountain just east of Canberra, and when there's storms out to sea, I can often see the tops of them, with lightning coursing all over them. They're hundreds of kms away. sometimes even people in Canberra can see them.

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#1005502 - 11/08/2011 15:37 Re: Clouds on the horizon over the sea [Re: ant]
Big_Pete Offline
Weatherzone Addict

Registered: 19/12/2004
Posts: 1955
Loc: Perth
Same in Albany. At night in winter I can see coldie tops illuminated by occassional CC's over 200 kms south of Albany. And there's nearly always cloud on the coast even when a high is settled in the bight and we get dry N'lies.

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#1006117 - 15/08/2011 13:15 Re: Clouds on the horizon over the sea [Re: Big_Pete]
ROM Offline
Meteorological Motor Mouth

Registered: 29/01/2007
Posts: 6628
The following very simple explanation on why clouds are seen off the coast early in the morning and then dissappear is from a ballooning website




The SST's off the Queensland coast are quite high at the moment and the warm tropical Leeuwin current is running strongly off the WA Albany coast
Ocean temps for the last 6 days around Australia's coastal waters can be found in the CSIRO's marine division point and click temp maps

The BOM has ocean temps and current maps here. Linky

Low level clouds are often seen in the early morning in places like western Victoria and as we glider pilots,say, they "burn" off a couple of hours into the morning as the temperature rises and the relative humidity declines.

I have seen lightning in the tops of thunderstorms from well over 350 kms away.
We left Yarrawonga on the Murray in eastern Vic to travel to Horsham some 400 kms to the west "As the cocky flies" soon after dark one evening and could see glowing flashes of lightning playing amongst the cloud tops far to the west.
We eventually reached that thunderstorm line which was rapidly moving eastwards at Donald , nearly 300 kms from when we first saw those lightning flashes in the cloud tops and that storm line had been moving towards us for some 4 hours before we reached it so 350 kms is a very conservative estimate on how far away you can see lightning in cloud tops on a clear night.

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#1006216 - 16/08/2011 10:13 Re: Clouds on the horizon over the sea [Re: ROM]
ROM Offline
Meteorological Motor Mouth

Registered: 29/01/2007
Posts: 6628
Dunno what happened to that "Land Breeze" pic as it came up OK when I posted it so here it is again.

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#1066059 - 28/01/2012 09:17 Re: Clouds on the horizon over the sea [Re: ROM]
ozthunder Offline
Weatherzone Addict

Registered: 23/09/2001
Posts: 3346
Loc: Mt Warrigal, NSW, Australia
There are often convergence zones at various strengths and degrees with 10-100km of the coast. The land/sea breeze are a common one. On other occasions it is dry offshore winds under a steep lapse rate, as the winds blow across the ocean they finally pick up enough moisture to produce convection.

Sydney gets convergence zone showers quite a bit in weak SE winds, the winds often swing SW overnight, but are still S/SE 20-50kms offshore, generally the convergence starts approaching the coast soon after sunrise, with a short period of showers around 10am as winds become SE again.
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#1066121 - 28/01/2012 10:07 Re: Clouds on the horizon over the sea [Re: ozthunder]
Steve777 Offline
Meteorological Motor Mouth

Registered: 20/10/2011
Posts: 5027
Loc: Artarmon (Sydney North Shore)
This has been very common in Sydney this summer, with a predominance E-SE winds. It will be partly cloudy in the early morning, with many sunny breaks. A cloud band will roll in around 9:00 - 9:30AM and it will soon be completely overcast. I've been surprised at how regular, even predictable, this has been this year.

The overcast hangs around for several hours, sometimes with light showers, at least on higher ground. The cloud will normally break up during the afternoon, although the timing is less predictable - basically anywhere between 1:00 and 4:00PM, with mid to late afternoon having lengthy sunny periods again.

We should have a name for it - taking a leaf from California, 'Noon Gloom' or 'Midday Grey' perhaps?


Edited by Steve777 (28/01/2012 10:13)

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#1104463 - 17/05/2012 06:13 Re: Clouds on the horizon over the sea [Re: Steve777]
LQQKN Offline
Weatherzone Addict

Registered: 24/08/2007
Posts: 1438
Loc: , tweed coast
All I know is the diffrence between sea and land temperature at the moment the ocean
Is stil warm and sustains showers an sometimes awesome cloud structure offshore this time of year also showers can be more heavy in the morning then seem to dry out in the arfternoon can be from cooler land tempretures overnight and warm ocean temps. If there was an island 100km east of tweed omg would get so much rainfall.

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