Tasman Low and Ex-TC Donna - May 11-12

Archive of NZ Weather & Climate
Forum rules
These topics are a read-only archive and may be subject to out-of-date information.

For today's weather discussion head to: New Zealand Weather & Climate
Razor
Moderator
Posts: 5354
Joined: Fri 10/02/2006 15:14
Location: Halswell, Christchurch

Tasman Low and Ex-TC Donna - May 11-12

Unread post by Razor »

Just pop this here for future reference, a long way to go but but interesting pictures, and to be fair the GFS has done a fairly good job of predictions for the ex TCs lately as far as a week out. But probably' just for fun at this stage
You do not have the required permissions to view the files attached to this post.
Christchurch Rocks
User avatar
Tornado Tim
Moderator
Posts: 4920
Joined: Sun 19/10/2008 17:17
Location: Raglan, Waikato / Hillcrest, Hamilton

Re: General May Weather

Unread post by Tornado Tim »

Argh, to be honest the forecast isnt even worth talking about at this stage. Mainstream media is alluding to NZ is going to be hit, even though the forecast is over 1 week prognostic which is notorious for being incorrect.

So many model watchers on FB saying its going to happen and then point the source of truth at 7 day+ prognostic GFS model run, yup that makes it credible, yeah right!
Incredibly frustrating! >_
NZAPStrike.net - NZ Aus Pacific Strike Network
Razor
Moderator
Posts: 5354
Joined: Fri 10/02/2006 15:14
Location: Halswell, Christchurch

Re: General May Weather

Unread post by Razor »

Tornado Tim wrote:Argh, to be honest the forecast isnt even worth talking about at this stage. Mainstream media is alluding to NZ is going to be hit, even though the forecast is over 1 week prognostic which is notorious for being incorrect.

So many model watchers on FB saying its going to happen and then point the source of truth at 7 day+ prognostic GFS model run, yup that makes it credible, yeah right!
Incredibly frustrating! >_
Hence the qualifications in the post above. Models have struck it lucky with last two ex TCs, so lets out of interest follow progress on this in the coming days.
Christchurch Rocks
User avatar
Rogue
Posts: 189
Joined: Sun 14/08/2011 12:35
Location: Kapiti Coast

Re: General May Weather

Unread post by Rogue »

Not ideal, flying out to the states on May 13 ...
User avatar
Thunder081
Posts: 470
Joined: Wed 22/08/2012 00:10
Location: Christchurch

Re: General May Weather

Unread post by Thunder081 »

Tornado Tim wrote:Argh, to be honest the forecast isnt even worth talking about at this stage. Mainstream media is alluding to NZ is going to be hit, even though the forecast is over 1 week prognostic which is notorious for being incorrect.

So many model watchers on FB saying its going to happen and then point the source of truth at 7 day+ prognostic GFS model run, yup that makes it credible, yeah right!
Incredibly frustrating! >_
Yes it is annoying and it's going to keep happening
WW does the same sometimes like with Cyclone Winston last year. If we were to raise more awareness about proper use of the models the media wouldn't listen cause they want more clicks on there websites for more ad revenue right?
Wellington southerly front timelapse: www.youtube.com/watch?v=MBl3hsuIg2Q
Manukau heads obs
Posts: 12305
Joined: Mon 10/03/2003 16:30
Location: West Coast Road, Manukau Peninsula, North Island

Re: General May Weather

Unread post by Manukau heads obs »

WW have backed tracked..their wording is now using like lots of uncertainty wheras a couple of days ago their words were like using likely...
I think they get a bit too excited with TC's and try to be the first to make a call...so they can then claim to have exclusively called it...I think they were lucky with the last cyclone, it did what the models predicted (mind you the models came into agreement quickly..but this time they have not, and that is where you need to use your judgement and not rely on just one mode..otherwise you just model watching..and anyone can do that
Image
Brian Hamilton, weather enthusiast. My weather dataEmail: [email protected]
User avatar
Thunder081
Posts: 470
Joined: Wed 22/08/2012 00:10
Location: Christchurch

Re: General May Weather

Unread post by Thunder081 »

Manukau heads obs wrote:WW have backed tracked..their wording is now using like lots of uncertainty wheras a couple of days ago their words were like using likely...
I think they get a bit too excited with TC's and try to be the first to make a call...so they can then claim to have exclusively called it...I think they were lucky with the last cyclone, it did what the models predicted (mind you the models came into agreement quickly..but this time they have not, and that is where you need to use your judgement and not rely on just one mode..otherwise you just model watching..and anyone can do that
I reckon it's either cause the media makes an article saying NZ could be hit 5 - 7 days + out based on one model then a lot of people ask WW what's going to happen so WW makes a prediction on it. Or WW makes a prediction with a click bait title that'll do the rounds on facebook meaning more people will tune into WW for the coming days after the initial prediction so that way WW will get more traffic to its website. Aaarrrggg it can really frustrate me, sometimes I call WW and certain media (Stuff, NZHerald) 'the super over exaggerators'
Wellington southerly front timelapse: www.youtube.com/watch?v=MBl3hsuIg2Q
Manukau heads obs
Posts: 12305
Joined: Mon 10/03/2003 16:30
Location: West Coast Road, Manukau Peninsula, North Island

Re: General May Weather

Unread post by Manukau heads obs »

some of the models have it back on the cards for it merging with a tasman low by the end of the week
(i.e proving a moisture feed for the tasman low and energising that...this I think is a likely scenario)
Image
Brian Hamilton, weather enthusiast. My weather dataEmail: [email protected]
User avatar
NZstorm
Posts: 11333
Joined: Mon 10/03/2003 19:38
Location: Grey Lynn, Auckland

Re: General May Weather

Unread post by NZstorm »

Manukau heads obs wrote:some of the models have it back on the cards for it merging with a tasman low by the end of the week
(i.e proving a moisture feed for the tasman low and energising that...this I think is a likely scenario)
Yes, the ex TC is a slight complication in the forecast this week. Have to see what the 00Z model runs come up with today.
James
Posts: 33
Joined: Mon 06/03/2017 07:58
Location: Havelock North

Re: General May Weather

Unread post by James »

I can remember the days when weather was only a story in the media when something abnormal occured. Now our local daily (HB Today) has a weather story every day, complete with umbrellas, or ducks, or kids, whatever, telling us what to expect in the next few days. :>
User avatar
David
Posts: 7636
Joined: Sat 18/08/2007 21:02
Location: Howick, Auckland

Re: General May Weather

Unread post by David »

Manukau heads obs wrote:some of the models have it back on the cards for it merging with a tasman low by the end of the week
(i.e proving a moisture feed for the tasman low and energising that...this I think is a likely scenario)
Whoa, latest GFS is showing 140 mm here on Thursday... certainly something to watch!
Image
User avatar
Thunder081
Posts: 470
Joined: Wed 22/08/2012 00:10
Location: Christchurch

Re: General May Weather

Unread post by Thunder081 »

Yes it is now something to watch
Some of the media/FB weather forecasters need to know the basic guide of using models.

1 - 2 days out: Make predictions, compare multiple model scenarios
3 days out: Something to watch more closely
4 - 5 days out: Just something to watch
6 - 7 + days out: Why am I looking here? lol

Latest GFS (1800-07-05-2017) shows a stormy scenario but.. it'll probably flip flop.
Wellington southerly front timelapse: www.youtube.com/watch?v=MBl3hsuIg2Q
Manukau heads obs
Posts: 12305
Joined: Mon 10/03/2003 16:30
Location: West Coast Road, Manukau Peninsula, North Island

Re: General May Weather

Unread post by Manukau heads obs »

and the BOM model is showing it too
it looks stronger overnight if you ask me
Image
Brian Hamilton, weather enthusiast. My weather dataEmail: [email protected]
Razor
Moderator
Posts: 5354
Joined: Fri 10/02/2006 15:14
Location: Halswell, Christchurch

Re: General May Weather

Unread post by Razor »

Models certainly more variable in their trends spot this system than they were worth the last two
Christchurch Rocks
User avatar
NZstorm
Posts: 11333
Joined: Mon 10/03/2003 19:38
Location: Grey Lynn, Auckland

Re: General May Weather

Unread post by NZstorm »

Upper North Island will get a good soaking from an upper level trough Thursday night/early Friday and then exTC Donna passing close to East Cape later Friday.
spwill
Posts: 10081
Joined: Sun 29/06/2003 22:39
Location: Mt Eden Auckland

Re: General May Weather

Unread post by spwill »

NZstorm wrote:Upper North Island will get a good soaking from an upper level trough Thursday night/early Friday and then exTC Donna passing close to East Cape later Friday.
It will be a warmer week after a cool week last week, AK temp range today 10-20C.
Cooler flow to affect the country at the end of week.
User avatar
NZstorm
Posts: 11333
Joined: Mon 10/03/2003 19:38
Location: Grey Lynn, Auckland

Re: General May Weather

Unread post by NZstorm »

The latest ECMWF has the ex TC coming onto upper North Island!
You do not have the required permissions to view the files attached to this post.
Manukau heads obs
Posts: 12305
Joined: Mon 10/03/2003 16:30
Location: West Coast Road, Manukau Peninsula, North Island

Re: General May Weather

Unread post by Manukau heads obs »

yes, that is what the BOM (access) model has been showing for a while now..and has it deepening as it does so, combining with the tasman low
also there looks to be another cyclone developing near samoa
(when the conditions are ripe for one, you often get another)
Image
Brian Hamilton, weather enthusiast. My weather dataEmail: [email protected]
Manukau heads obs
Posts: 12305
Joined: Mon 10/03/2003 16:30
Location: West Coast Road, Manukau Peninsula, North Island

Re: General May Weather

Unread post by Manukau heads obs »

the media are terrible
7am TV1 breakfast:
"TC donna is intensifying and heading towards New caledonia, where the cat 5 cyclone is expected to hover over new caledonia until thursday"
Image
Brian Hamilton, weather enthusiast. My weather dataEmail: [email protected]
Blowy
Posts: 103
Joined: Tue 10/03/2015 12:21
Location: Hawkes Bay

Re: General May Weather

Unread post by Blowy »

Why no separate 'TC Donna' page?
I wonder if this one is the 'wolf' after all the recent 'cry wolf' storms.... no one taking seriously it seems.
User avatar
Nev
Moderator
Posts: 6332
Joined: Tue 07/03/2006 15:24
Location: Waiheke Island, Hauraki Gulf

Re: Tasman Low and Ex-TC Donna - May 11-12

Unread post by Nev »

^ Done... :-)
jamie
Posts: 5907
Joined: Fri 25/02/2011 21:35
Location: Hamilton NZ

Tasman Low and Ex-TC Donna - May 11-12

Unread post by jamie »

I've been watching the models. Seems as though they are coming into better alignment over the past 24 hours and the general trend today has been for the cyclone to pass closer and closer to nz with a couple models putting a direct hit in the cards.

Something to watch!
Manukau heads obs
Posts: 12305
Joined: Mon 10/03/2003 16:30
Location: West Coast Road, Manukau Peninsula, North Island

Re: Tasman Low and Ex-TC Donna - May 11-12

Unread post by Manukau heads obs »

it looks like it has moved more east ?
although that might be just it being toppled over by the jet stream..i.e the LLCC is further west of the high cloud

the cloud sheet between the 2 low centers is developing more and more...could be come heavy falls of rain for the NI
Image
Brian Hamilton, weather enthusiast. My weather dataEmail: [email protected]
User avatar
Tornado Tim
Moderator
Posts: 4920
Joined: Sun 19/10/2008 17:17
Location: Raglan, Waikato / Hillcrest, Hamilton

Re: Tasman Low and Ex-TC Donna - May 11-12

Unread post by Tornado Tim »

Manukau heads obs wrote:it looks like it has moved more east ?
Yes, Ensemble Mean Analysis over CMC, GFS, ECMWF, UKMO models combined has a more Eastward progression over the past 24 hours.

UKMO has more North NZ Interaction with Donna than any other model, I would classify it as an outlier at this stage, however its ensemble member output is much more concise.

Atm all numerical atmospheric model are still having problems with discerning the track from 24-48 hour+ prognostic forecast with huge discrepancies between ensemble members.

Far too much discrepancy for a call at this stage, and it seems Metservice is also reserving judgement.

Anyway it seems the parts of North Island has at least a moderate to high chance of Heavy Rain, regardless wether it comes from the ex-TC or Low from the Tasman.
NZAPStrike.net - NZ Aus Pacific Strike Network
Manukau heads obs
Posts: 12305
Joined: Mon 10/03/2003 16:30
Location: West Coast Road, Manukau Peninsula, North Island

Re: Tasman Low and Ex-TC Donna - May 11-12

Unread post by Manukau heads obs »

Donna got her head completly lopped off last night by the jet stream
and those cloud tops have been blown off to the east
and so the true center is likely still just east of Noumea, I suggest

of more interest is baroclinic zone that has developed off Brisbane, and that one to the south of the remains of the cyclone
i.e there is alot of rain clouds building and are going to provide energy for the tasman low...
Image
Brian Hamilton, weather enthusiast. My weather dataEmail: [email protected]