Westerlies increasing?

Willoughby · Unread post by **Willoughby** » Mon 24/07/2006 01:27

With Perth finally getting it's first real rains of 2006 due to persistent easterlies and highs in the GA Bight.. being shafted now thanks to feeder jetstream bands coming off South America a little while ago and generating a strong frontal system.

With waters cooler than normal mostly right across Australia.. should that push the ridges of high pressure further north.. and give us an early spring-type pattern of west to southwesterlies? The Coral sea has eased back from being very hot in April (anomaly wise)... less lows bearing down? Of course we are now in the ENSO-neutral phase.. yet La Nina's characteristics still playing havoc of late over NZ..

The filtered 500mb height chart sure looks different to that of June.
Nodes have eased, right off almost.. enabling a westerly regieme to let loose below the forties.

What are your opinions on this guys?

RWood · Unread post by **RWood** » Mon 24/07/2006 07:06

I guess it's wait and see. Interesting that because of the high rainfall locally (258 mm in W'gton city so far, will be the highest since 1974's 282) people have still talked of the cold, but temps so far in July have been a bit above average here (and by 1C in Hawkes Bay and BOP), according to a short comment from NIWA's Stuart Burgess.

Edit: I'm hoping the fine clear day y'day and expected today/tomorrow are harbingers of this change...

Manukau heads obs · Mon 24/07/2006 07:08

i would agree.....after a long run of the weather pattern we have had, it would be about time to go back to WSW quarter winds....the shift can happen abruptly...

spwill · Unread post by **spwill** » Mon 24/07/2006 08:55

Can't remember a spring when the westerlies didn't blow.

TonyT · Unread post by **TonyT** » Mon 24/07/2006 11:28

Some good thoughts there Foggy. I think a brave prediction at this point would be that the SOI will stay substantially negative, and that a weak El Nino will develop over the next six months or so. In which case the next couple of months will show mainly pre-El Nino conditions, which would suggest the westerlies will be broken fairly regularly by out-of-position depressions and anticyclones. In other words, more of the same.

Cameo1 · Unread post by **Cameo1** » Mon 24/07/2006 11:30

Foggy Hamilton wrote:With Perth finally getting it's first real rains of 2006 due to persistent easterlies and highs in the GA Bight.. being shafted now thanks to feeder jetstream bands coming off South America a little while ago and generating a strong frontal system.

With waters cooler than normal mostly right across Australia.. should that push the ridges of high pressure further north.. and give us an early spring-type pattern of west to southwesterlies? The Coral sea has eased back from being very hot in April (anomaly wise)... less lows bearing down? Of course we are now in the ENSO-neutral phase.. yet La Nina's characteristics still playing havoc of late over NZ..

The filtered 500mb height chart sure looks different to that of June.
Nodes have eased, right off almost.. enabling a westerly regieme to let loose below the forties.

What are your opinions on this guys?

Eh.....?

Michael · Unread post by **Michael** » Mon 24/07/2006 12:19

They blow well into spring and well into summer now,They will always come while everywhere else is in the mid 20s it will only be 17 here,A continental climate is far better,more extremes,more interesting plus reliable weather

squid · Unread post by **squid** » Mon 24/07/2006 12:22

I dont think that el nino will develop I think it will remain nutural for the time being.

spwill · Unread post by **spwill** » Mon 24/07/2006 12:32

Michael said,

They will always come while everywhere else is in the mid 20s it will only be 17 here,

Northland and Auckland are still the warmest part in NZ overall at that time of the year despite those spring West/South Westerlies

C-Nimbus · Unread post by **C-Nimbus** » Mon 24/07/2006 12:51

Fogster/TonyT/NZstorm/MHO can you correct me on this....

with regards to SOI, i always thought that this was literally the latitude of alternating highs and lows relative to a certain time of the year.

For eg, if we simplified things and said that highs and lows alternate with each other (ie one after the other), then as seasons change etc etc, the latitude of these highs and lows moves up or down depending on the time of year.

I have done a rough drawing and attached it as a pdf.

My descriptions and drawing are rubbish, but hopefully you can get where I'm going with this one!

your comments and help are most welcome

Willoughby · Unread post by **Willoughby** » Mon 24/07/2006 13:04

Was it 1972 or 1 when June was the coldest? What were the conditions of the year running up to that 1974 July Wellington event, Rwood? Were we in a weak La Nina phase..? I see during those years we were in a cool-PDO phase (most of that decade anyway) yet most of this decade so far has been warm.. is the PDO a useful tool here.. or do the waters between Australia and Antarctica play a more critical role in our wx system..(or is that already accounted for)
What was Perth or Adelaide's rainfall like in 1972/1974? (as a comparasion)

Because this cold pattern gobsmacked NIWA.. it must've been a very freakish event.. polar and sub-tropic jetstream coming 'too close' to eachother of late?

Cheers,
Willoughby

Can't remember a spring when the westerlies didn't blow.

They only really blew for one week last year, in early October. Michael was shunned.

RWood · Unread post by **RWood** » Mon 24/07/2006 14:01

Foggy Hamilton wrote:Was it 1972 or 1 when June was the coldest? What were the conditions of the year running up to that 1974 July Wellington event, Rwood? Were we in a weak La Nina phase..? I see during those years we were in a cool-PDO phase (most of that decade anyway) yet most of this decade so far has been warm.. is the PDO a useful tool here.. or do the waters between Australia and Antarctica play a more critical role in our wx system..(or is that already accounted for)
What was Perth or Adelaide's rainfall like in 1972/1974? (as a comparasion)

Because this cold pattern gobsmacked NIWA.. it must've been a very freakish event.. polar and sub-tropic jetstream coming 'too close' to eachother of late?

Cheers,
Willoughby

Can't remember a spring when the westerlies didn't blow.
They only really blew for one week last year, in early October. Michael was shunned.

It was 1972 (June and August cold and frosty, July relatively mild). 1972 was an El Nino year with a lot of southwesterlies (2686 hrs of sun in Blenheim, only about 1472 in Invercargill), following strong La Nina in 1971. Couldn't comment too much on the PDO importance. July 1974 was in a long and strongish La Nina which developed mid-1973 and persisted thru into 1976 apart from short weakenings.

But do note that July hasn't been cold, just wet in some places (could possibly surpass 1974 at Kelburn, and if it does, one has to go to pre-1928 (pre-Kelburn) records to find a wetter one.

janewaystv should have a wealth of info on the Aussie data...

On an irrelevant personal note, my 2nd daughter was born in May 1972, heralding a lot of cold SW or frosty anticyclonic weather. Her niece was born on June 21 this year but the coldness has been more uneven since then I guess.

RWood · Unread post by **RWood** » Mon 24/07/2006 14:04

Quote:
Can't remember a spring when the westerlies didn't blow.

They only really blew for one week last year, in early October. Michael was shunned.

Spring 2005 in W'gton almost matched 1958 for atypicality (both being vastly more pleasant than normal), and Spring 2005 was preceded by the "best" ever August.

Michael · Unread post by **Michael** » Mon 24/07/2006 14:13

Thats Wellington,There was a week or so of proper westerlies then but the rest of the spring apart from Aug-early Sep last year was that scum weather like today where it rained small amounts and the wind was always there 24/7 in varying speeds

RWood wrote:Quote:
Can't remember a spring when the westerlies didn't blow.

They only really blew for one week last year, in early October. Michael was shunned.

Spring 2005 in W'gton almost matched 1958 for atypicality (both being vastly more pleasant than normal), and Spring 2005 was preceded by the "best" ever August.

RWood · Unread post by **RWood** » Mon 24/07/2006 14:37

Michael wrote:Thats Wellington,There was a week or so of proper westerlies then but the rest of the spring apart from Aug-early Sep last year was that scum weather like today where it rained small amounts and the wind was always there 24/7 in varying speeds
RWood wrote:Quote:
Can't remember a spring when the westerlies didn't blow.

They only really blew for one week last year, in early October. Michael was shunned.

Spring 2005 in W'gton almost matched 1958 for atypicality (both being vastly more pleasant than normal), and Spring 2005 was preceded by the "best" ever August.

Couldn't comment on the northern zones but will leave you and Foggy to debate that one

janewaystv · Unread post by **janewaystv** » Mon 24/07/2006 15:11

See my syd weather obs for more details.

RWood-re the wet July of 1974, what was the prevailing wind? Sydney for July 1974 saw only 14mm (the only drier than normal month of 1974) with persistant W winds.

RWood · Unread post by **RWood** » Mon 24/07/2006 15:23

1974 was a muddle of anticyclonic, easterly and southerly. Jul 1974 had a lot of cyclonic NW flow with several very wet days. Jan was coolish, sunny and anticyclonic. Feb was exceptionally warm in the northern half of the NI but very cloudy over most of the SI with only 70 hrs at Timaru (about 19% of possible) - dull southerlies and easterlies there. March was cold dry and sunny, with persistent southerlies. April was a bizarre month that I described in detail in an older post. W'gton city had 1406mm rain in April-Oct -well over annual mean. Nov and Dec were anticyclonic, very sunny and dry in central NZ especially.

Michael · Unread post by **Michael** » Mon 24/07/2006 15:24

Sounds like that was a good year

RWood wrote:1974 was a muddle of anticyclonic, easterly and southerly. Jul 1974 had a lot of cyclonic NW flow with several very wet days. Jan was coolish, sunny and anticyclonic. Feb was exceptionally warm in the northern half of the NI but very cloudy over most of the SI with only 70 hrs at Timaru (about 19% of possible) - dull southerlies and easterlies there. March was cold dry and sunny, with persistent southerlies. April was a bizarre month that I described in detail in an older post. W'gton city had 1406mm rain in April-Oct -well over annual mean. Nov and Dec were anticyclonic, very sunny and dry in central NZ especially.

RWood · Unread post by **RWood** » Mon 24/07/2006 15:26

From memory Auckland had over 2200 hrs sun, much more than Napier and Gisborne - the latter approximately matched by Greymouth.

Michael · Unread post by **Michael** » Mon 24/07/2006 15:28

I knew the 70s had better weather than these days

Razor · Unread post by **Razor** » Tue 25/07/2006 17:43

RWood wrote: On an irrelevant personal note, my 2nd daughter was born in May 1972, heralding a lot of cold SW or frosty anticyclonic weather. Her niece was born on June 21 this year but the coldness has been more uneven since then I guess.

No doubt highly relevant that I was also born in 1972, in May. I can confirm I'm not replicating any cycles of birth this year though....
A vintage year that was

tich · Unread post by **tich** » Wed 26/07/2006 21:52

I think many winter months that have had well below normal temperatures have been when conditions have been very frosty with low night temps, eg July 2001. Wet months like this July in the North Island may have felt cold with the cloud preventing days from getting very mild, but nights will have been warmer than average.

I think winter months with persistent westerlies have tended to me milder than normal, an example being July 1964. This should hold true especially for eastern areas.

RWood · Unread post by **RWood** » Thu 27/07/2006 09:09

Yes. July 1986 had a big southerly storm at the start of the month, but thereafter was dominated by southwesterlies with frosty nights at times, sunny in eastern places and Wellington - which had a much lower rainfall than for this July. From recall it was significantly colder than average over the country because of the frosty nights.

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