Spring Westerlies

[spwill]

Brian wrote,

my sept average temperature so far is now 0.4oC colder than normal
and I see the tasman sea temperatures a bit below normal too
despite sunshine being up for auckland....

Perhaps more cooling at night for Auckland than normal with the dry clear weather and drier ground conditions.

[Manukau heads obs]

yes, I was just thinking that....clearer night time skies have given us colder night time temperatures
(ps, I now have a night time cloud sensor working (works on the black body principle)
see
http://www.weather-display.com/windy/gb/extragraph.html
i.e when its less than the normal outside temperature, the sky is clear (and clearer the lower it gets)

[Nev]

Interesting. Another cooler than normal month! I havn't really been following the temps but I'm sure August was below average as well in AK.

According to NIWA, despite the wet winter in Akld (150% above normal rainfall), August was only -0.1°C below average and June and July were warmer than average. Sunshine was normal in August and June but only 87% of normal in July (the wettest month).

May overall however was the coldest it's been since 1992. In Akld it was -1.2°C below average, even though sunshine was 125% above normal (rainfall was normal).

Btw, October in Akld is typically warmer, drier and sunnier than September, just a hellava lot windier!

[David]

I've recorded a mean low of 8.1oC and a mean high of 17.7oC this month (very similar to both 2006 and 2007), I thought this was about average for here - but I don't have any long term records to compare against.

I see you have an average high of only 15.8oC there Brian, maybe there has been lots of W/SW days this month where the west coast doesn't warm up as much as further inland.

[Manukau heads obs]

I also live at about 280 feet, so there is about a 0.4 oC difference to somone living at sea level...but, yes, being close to the west coast, not much land heating has occured compared to further inland
will be interesting to see what niwa data shows up for the average for sep....

[Manukau heads obs]

this next cold front could be interesting for westen NI places 2 nite according to MS severe weather outlook

[NZstorm]

this next cold front could be interesting for westen NI places 2 nite according to MS severe weather outlook

I have been watching this front in the modeling for a few days now and I don't think the moisture will be good enough for thunder around Auckland with the front given only marginally cold upper air. I am thinking maybe a low risk over NW Northland or out to sea where the dp may be a little higher. September has been a month of relatively dry airmasses which is typical of early spring I guess.

Just add that tonights upper wind profile is strong and backing with height which would be favourable for organised convection. Pity we will not end up with CAPE. Forecast dps are 13C which look a bit low.

[Manukau heads obs]

looks to be signs of a clear back edge squall line developing now .....
yes, the DP is low (left over southerly) at the moment...should lift before the front....but yes 13 is not great....

[jamie]

[quote="Manukau heads observer"]looks to be signs of a clear back edge squall line developing now .....[quote]

what does that mean?

[Manukau heads obs]

maybe not worded very well
just means the cold front is becoming more defined/sharper, at the clearance to the colder SW change

[jamie]

ohhh gotcha now... thanks

[spwill]

I have been watching this front in the modeling for a few days now and I don't think the moisture will be good enough for thunder around Auckland with the front given only marginally cold upper air. I am thinking maybe a low risk over NW Northland or out to sea where the dp may be a little higher.

The thunderstorm activity that was with the Front in the central Tasman earlier today has pushed north and looks to have died out now.

[Manukau heads obs]

looks to be some usefull rain coming with it though (after so far a drier than normal (so far) (was needed)) september

[Nev]

Only about 1mm here last night. But yes, a very dry September - maybe about 40-50% of normal rainfall for more central Akld areas. Similar story in the other main cities except for Wellington, which will probably end up with at least 160% of normal rainfall. My guess however is that NIWA will show normal or slightly above normal temps for Akld this month. I also think NIWA's sunshine summary might look something like this...

Estimate of September 2008 Sunshine - (in descending order of hours)
1. Akld - Well above average
2. Hmtn - Above average
3. Chch - Below average
4. Dndn - Above average
5. Wgtn - Well below average

[spwill]

7.8mm for central Auckland off the Front, good for local farming


The start of October looks unsettled however a High near northern NZ might be close enough to keep much of the Frontal cloud/ rain to our south.

[RWood]

Only about 1mm here last night. But yes, a very dry September - maybe about 40-50% of normal rainfall for more central Akld areas. Similar story in the other main cities except for Wellington, which will probably end up with at least 160% of normal rainfall. My guess however is that NIWA will show normal or slightly above normal temps for Akld this month. I also think NIWA's sunshine summary might look something like this...

Estimate of September 2008 Sunshine - (in descending order of hours)
1. Akld - Well above average
2. Hmtn - Above average
3. Chch - Below average
4. Dndn - Above average
5. Wgtn - Well below average

Sounds right Nev (from my current distant perspective) as Wgton crawled to about 126 by 29th. As a wet cloudy combination may have to go back to about 1992 to beat it. Well done AK!

[Myself]

Sounds right Nev (from my current distant perspective) as Wgton crawled to about 126 by 29th. As a wet cloudy combination may have to go back to about 1992 to beat it. Well done AK!

Dare I say, that is slightly better than I expected....which says a lot about how dull this month has been. Probably will notch up a few extra hours on that today to push it just over 130.

[Nev]

So much for the 'Equinoctial Gales' - I see NIWA is expecting October to December to be 'dry and settled' in their latest Seasonal Outlook...

Mean sea level pressures are likely to be higher than normal, especially over the South Island, resulting in lighter winds than usual over the country and periods of easterlies affecting the North Island. This means that the normal westerly gales, typical of October and November, are likely to be less frequent.

Air temperatures are likely to be average in the North Island, and average or above average in the South Island. Sea surface temperatures around New Zealand are expected to remain near normal.

Rainfall is likely to be near or below normal over the entire country...

[Manukau heads obs]

less frequent is the key word
but yet t he media is headlining it as a calm hot spring!
also in the hearald yesterday, phillip duncan was quoted as saying the summer will be cooler, due to more NE / less SW winds, because its not going to be el nino (or la nina), or auckland
i dont think thats correct
el nino summers are cooler in auckland because of the SW winds come from further south than NE winds do, and you get those anticyclonic gloom days that only warm up in the afternoon

[Michael]

It says in My herald "analyst Phillip Duncan said the country was in a nuetral weather period that favoured prevailing westerly winds meaning a cooler summer was likely for Auckland....."[quote=]
also in the hearald yesterday, phillip duncan was quoted as saying the summer will be cooler, due to more NE / less SW winds, because its not going to be el nino (or la nina), or auckland
i dont think thats correct
[/quote]

[Nev]

less frequent is the key word
but yet t he media is headlining it as a calm hot spring!

NIWA also says "lighter winds than usual" though - I guess they must mean the overall average?
But yes, I don't see how the media can interpret temps being "average in the North Island, and average or above average in the South Island" as being "a calm, hot spring"?

[Manukau heads obs]

also, whats the sun being in a solar minimum (currently) going to do (e.g for our summer)?

good thing we have global warming to counteract that?

[TonyT]

So much for the 'Equinoctial Gales' - I see NIWA is expecting October to December to be 'dry and settled' in their latest Seasonal Outlook...

Not exactly news - that sentiment has been in other seasonal predictions since August.

[Nev]

Yes, but I think it's the first time they actually stated that "the normal westerly gales, typical of October and November, are likely to be less frequent."

Ah, just found the NZ Hearld / Weather Watch article. Doesn't mention "more NE / less SW winds" though - (for those taking advantage of the 'foe function') it says...

...the country was in a "neutral" weather period that favoured prevailing westerly winds, meaning a cooler summer was likely for Auckland.

But yes, I would have thought that "neutral" would mean a more normal summer, rather than "a cooler summer than usual"?

[Manukau heads obs]

yes, the point is, a el nino would give more SW winds and cooler
but since no elnino and no la nina (might even go back to a weak la nina?) then less SW winds than normal
(as being in some sort of el nino is more normal (because they last longer)
(but what is normal anyway (just the average of the extremes!))