January General Weather 2008

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January General Weather 2008

Postby Turbo » Tue Jan 01, 2008 7:34 am

Perth radar showing some showers heading south, and the Geraldton radar shows widespread showers. Hopefully could get to us later this afternoon to cool us down but I'm sure the Perth Forcefield will make sure it stays dry. :roll:

BOM saying we could get some thundery showers tomorrow, but none of the models seem too excited about it.

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Postby craigperth » Tue Jan 01, 2008 11:52 am

Dont know turbo... they are saying chance of thunder storm tonight/tomorrow... looking out at the sky its building to the east, nice dark grey clouds... although they are rather "flat" but it feels like storm weather if that makes sense... (yeah I cant read the maps properly as yet! Oh Dear I hear you all sigh! :oops: :P )

But it FEELS warm and humid and wierd if you know what i mean... I hope we do get a good storm... I have spent 4 full days in the garden so the plants could do with a good drink :)

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Postby Turbo » Tue Jan 01, 2008 1:07 pm

But it FEELS warm and humid and wierd if you know what i mean... I hope we do get a good storm... I have spent 4 full days in the garden so the plants could do with a good drink Smile


Mate I reckon YOU could do with a good drink :lol:

Humidity is quite low (25% at Perth) and while the BOM has forecast thundery showers, they do expect them to be fairly light. I hope we get something tonight though!

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Postby craigperth » Tue Jan 01, 2008 1:11 pm

Mate I need a few drinks... I guess when your working in the garden which is damp it does not matter what the humity levels are your going to feel hot and sticky no matter!

Yeah I hope they are not to light... bring on the east coast weather!

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Postby Tim S » Tue Jan 01, 2008 2:36 pm

That area of light showers is still making its way down the coast, it doesnt seem like its weakened or dissipated yet, though its still a fair distance from the metro area. ;)

I imagine any storms we do get will be early tomorrow morning sometime between 4 and 10am. Its good that we wont get much rain out of them (if any), if we do it will be a sticky 38C tomorrow.
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Postby Blue Skies » Tue Jan 01, 2008 5:17 pm

Looks like the Perth Force Field has kicked in again.

Not looking forward to tomorrow, the humidity is likely to be a killer! Nor am I looking forward to next week either, with 39 and 40 forecast again. :( :(
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Postby Fu Manchu » Tue Jan 01, 2008 5:34 pm

Blue Skies wrote:Looks like the Perth Force Field has kicked in again.

Not looking forward to tomorrow, the humidity is likely to be a killer! Nor am I looking forward to next week either, with 39 and 40 forecast again. :( :(


someone beat me to it :lol:
The first day of the year and the force field has been switched on :D

Happy New "weather" everyone :D

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Postby davo » Tue Jan 01, 2008 8:09 pm

Hey I was wondering, with the force field effect clearly in full swing today, why it is mainly in summer this happens? Perhaps the curve of the earth means that the radar sees higher up (further off the ground) the further away the 'rain' is. Maybe it's virga which is falling from the cloud but evaporating before reaching the ground (not surprising since it's pretty hot and dry mith a breeze as well). As the cloud gets closer the radar sees lower and lower down, thus less and less rain. Since I can't see any rainfall from the Central West where this rain seems to have been all day, it makes sense to me. The force field just seems to happen too often for it to be chance!! Let me know what you reckon you experts 8) ...oh and anyone else too :wink:

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Postby Blue Skies » Tue Jan 01, 2008 8:18 pm

I think the common consensus is that the 'force field' effect is caused by the heat island that the metro area generates. All the bricks, concrete and bitumen roads in the city soaks up then radiates the heat back into the atmosphere. This would explain why it's more common in summer than winter. Heat islands are a well known effect of big cities. While our heat island seems to kill off rain, in the US the heat island caused by the city of Dallas (I think? one of the big Texas cities) actually causes thunderstorms to intensify slightly downwind of it.
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Postby peterperthh » Tue Jan 01, 2008 8:33 pm

I have heard about this heat island theory before, but as you said, only as a reason for intensifying weather rather than suppressing. There has been no recorded rainfall in the central west today, which also makes me think that very little rain was actually hitting the ground, and the forcefield is an illusion. Saying that a couple of weeks ago heavy totals were recorded north and east of us with the rainbands constantly decaying before they reached perth.

Tonight im actually glad the 'forcefield' was on as it stopped the rain long enough to treat us to a very memorable sunset on this the first day of the year :D



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Postby Tim S » Tue Jan 01, 2008 8:49 pm

Wow nice sunset pics Peterperthh! didnt get anything like that up my way, it just went dark when the sun went down. :lol:

As far as the forecfield theory goes, I would go with Davo's explanation it seems to make sense to me, especially considering no areas to the north recorded any rain. As Davo said it does happen quite often and would explain it very well, the heat island effect would only explain it if rainfall was increasing downwind as the increased heat and humidity would aid convection.
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Postby Fu Manchu » Tue Jan 01, 2008 9:12 pm

It is due to the mass clearing of land, the urban sprawl (there is info on this on the BOM site) are what causes "the force field".

On a local scale the perth suburban area does hold more heat than ever before. It has got to the size in the last 5-10 years to really influence local weather.
On the bigger scale, the wheatbelt also has an effect on our weather. Just look at the massive areas cleared on any sat weather pic. the wheat belt stands out prouder than a honeymooners proverbial. with that much forest and vegitation cleared the land also will heat more that it would when covered by the natural vegitation. In the case of the wheat belt I think it has enhanced storm activity by allowing stronger convection.

Is Perth worthy of a unique study into the effect it has. i mean just because Dallas or other cities do it one way, Is there something in the way of the greater surrounding area, combined with the worlds only warm water west coast current, combined with the heating of the city creating a unique effect on the weather?

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Postby Blue Skies » Wed Jan 02, 2008 6:03 am

Its raining at the moment here, looks like a line of showers coming down the coast again. I'm like others wondering how its going to get to 38 day if it cloudy all day. I suppose we shall see!
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Postby davo » Wed Jan 02, 2008 7:53 am

Yeah, well it seems Melanie is curving around the NW Cape nicely for us, but the prediction is for her to curve back to the NW. It would have to be a rare thing for that to happen, surely, but anyway if she does keep coming towards us, while she may not be a cyclone still perhaps overnight we could get a bit more moisture to fire things up in the trough. And I agree, Blue Skies. I don't see us getting to 38 today!

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Postby Vinny » Wed Jan 02, 2008 10:29 am

wasn't yesterday supposed to be 36??? it only got to 33...

i think 38 for today is not gonna eventuate ... i reckon maybe 32 or 33 today is the max .. unless the cloud goes....

if it was gonna be 38 it would be in the mid thirties by now and the winds usually north easterly... and so far it is in the mid twenties and the winds are not north easterly.

so i think perth will just be cloudy and dry today with about 32-33

maybe the bom wasn't thinking all this cloud was gonna be here when the prediction came out a few days back. :?:

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Postby Tim S » Wed Jan 02, 2008 10:44 am

The BoM are still going for 38C in the 11:30am forecast, I think it will get close we still have around 5 hours of heating left and there is a fair bit of clearer air to the NE. Also places like Dalwallinu were 32C at 11am and even Pearce was over 30C so theres not much heating needed. I'll expect we'll see the temp shoot up into the mid 30s by about 2-3pm where it will stay for most of the afternoon and probably some of the evening as there wont be much of a seabreeze for most of Perth. My forecast (guess ;)) is 36.6C :)
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Postby craigperth » Wed Jan 02, 2008 10:53 am

Melanie has begun her nw curve... she is also now a Tropical Low :( All gone :(

davo wrote:Yeah, well it seems Melanie is curving around the NW Cape nicely for us, but the prediction is for her to curve back to the NW. It would have to be a rare thing for that to happen, surely, but anyway if she does keep coming towards us, while she may not be a cyclone still perhaps overnight we could get a bit more moisture to fire things up in the trough. And I agree, Blue Skies. I don't see us getting to 38 today!

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Postby adamD » Wed Jan 02, 2008 11:54 am

Just came back from Osbourne Park and when I got out of the car at Joondalup Shops it felt 5C hotter than it was at Osbourne Park and that was an hour ago. Already at home here at Currambine it about 33C, so im sure it will get to around 38C later today.

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Postby Tim S » Wed Jan 02, 2008 12:16 pm

Yeah definitely hotter the further north you are, 37.3C at Pearce now and Ive got 35.4C on my home station.

Though if you go a lot further north, 44.1C at Geraldton and still going up! :shock: Thats an omnious sign for us tomorrow as I always look at Gero's temp the day before the trough goes through Perth and we quite regular get close to the temp they got the day before. Although I think the seabreeze should save us from anything that high tomorrow.
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Postby adamD » Wed Jan 02, 2008 12:31 pm

The big jump in temps are now starting to occur in the city. Surprised it jumped 6C at Pearce in only an hour.

Currently it has jumped to nearly 36C here in Currambine, 3C in just 30mins.

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