Hamilton South-westerlies

Willoughby · Unread post by **Willoughby** » Sat 23/08/2003 19:56

Hi, the last couple of weeks, Hamilton has recorded its highest temperatures with southwesterlies. Yesterday, I think our high was 19 degrees. Why are SW winds the warmest? It isn't as though we have a fohn wind...?

NZstorm · Unread post by **NZstorm** » Sat 23/08/2003 20:48

Hi,
I think you mean South easterlies. The wind direction has been east to south east last few days. There has been some fohn effect, hence the milder temperatures. Yesterday Auckland recorded 17.6C, today 17.1C.
But the air currently over us has its origins from the north.

I noticed some large shower cloud in the West Waikato direction again today.(looking south from Auckland). So the odd heavy shower about with the milder conditions.

Willoughby · Unread post by **Willoughby** » Sat 23/08/2003 21:59

oh true, SE. Where does Hamilton get it's fohn wind from? We had the meanest weather yesterday, hailstorms, over Hamilton at 3.30pm then moved west toward Raglan. Metservice didnt record it as there wasn't any at the airport.

Thunder · Unread post by **Thunder** » Sat 23/08/2003 22:35

Meanest but the most fun!

Very lucky! Christchurch's day will come!

Aaron Wilkinson

Michael · Unread post by **Michael** » Sat 23/08/2003 23:07

Foggy Hamilton wrote:oh true, SE. Where does Hamilton get it's fohn wind from?

Probably from the south generally or no wind at all gives its hot days

NZstorm · Unread post by **NZstorm** » Sun 24/08/2003 09:25

I am interested by the report of hail at Hamilton Saturday afternoon.
I drove to just south of Auckland to have a closer look at the cb's developing over the Waikato. To my disappointment, there was a lot of cloud about (not good for observing) and there was no static on the am band. But skies to the south looked dark and cloud tops quite high.
Not enough sunshine/thermal lift for thunder though.

Climpse of Cumulonimbus looking south from Mercer yesterday.

Willoughby · Unread post by **Willoughby** » Sun 24/08/2003 16:10

Yeah, from 3.10pm Friday to about 4.00 I saw about 5 flashes of lightning.
I'd still like to know where we get a fohn wind from. Is it the Kaimai - Mamaku ranges?!

Thunder · Unread post by **Thunder** » Sun 24/08/2003 17:56

Steven

That is the same problem we have down here, even though I have veiwed thunderstorms down here seriously (and for fun, it's a hobbie!) for only one season or year if you like, every time one has come, low cloud obscures a potential view of a towering Cb. Pretty much every time I've only seen a blacky grey bottom of a cloud come and go. Anyway, as Pete Mcghee would say:

wishing you strong convection
Aaron Wilkinson

NZ Thunderstorm Soc · Sun 24/08/2003 18:08

I'd still like to know where we get a fohn wind from. Is it the Kaimai - Mamaku ranges?![/quote]

Probably in a Se flow, a foehn effect would develop over the Waikato.
similar things happen when a cold SE wind can bring a foehn effect to parts of Westland.

JohnGaul
NZTS

NZstorm · Unread post by **NZstorm** » Sun 24/08/2003 18:19

A southerly or southeaster with its origins east of the NI is a Fohn wind for Hamilton. That is the air is coming over the central North Island from the Hawkes Bay. As southerly air is often cold, the Fohn wind is not hot but ofcourse it is very dry.

There is not really a Fohn affect for air coming in from the Bay of Plenty
(E/NE wind) over the kaimai/Coromandal ranges.

Manukau heads obs · Mon 25/08/2003 12:48

my 2 cents:
if the rain is spent on ranges, then the heating is more pronounced on leeward dry side
but wind blowing down off the kaimais into the waikato,and compressing, will warm up, and also, leaving more cloud in the BOP, and then getting heating off the ground from the sun shine , will warm up more than it was in the BOP to start with.....and coupled with the fact this low pressure area has warm air with it that originated from the north tasman,.....
thats what I think has been happening....

tich · Unread post by **tich** » Tue 26/08/2003 18:04

I'd still like to know where we get a fohn wind from. Is it the Kaimai - Mamaku ranges?!

I don't think the Kaimai and Mamaku ranges would be high enough to generate a significant fohn effect. I grew up in Rotorua, to the east and southeast of these ranges (although I don't think you can really describe the Mamaku plateau as a range), and our westerlies and northwesterlies weren't usually warm and dry like Canterbury's. We sometimes got a fohn effect from southeasterlies, so I guess the main eastern ranges of the North Island were the cause. Not as high as the Southern Alps, but considerably more elevated than the Kaimais. Sometimes, we'd get southerly/southerly showers or rain, but often it was dry when the east coast was wet. This could also explain why there were no reports of snow in the Waikato and BOP/Rotorua during this early July's polar blast - it certainly would've been cold enough, but the moisture was lacking.

I believe that warm fohn, southeasterly conditions in BOP/Waikato are caused more by southeasterly flows that originate from similar or lower latitudes pushed around a low to the east onto the North Island, rather than cold airflows from high latitudes.

Ben
Christchurch