NZ Weather Forum

Very very strong NWer at work up tram road, gusting over 90kph and building with 2 large shelter belt trees just come down and no Warning from MS for this.
This is what puts people off MS.

melja wrote:Very very strong NWer at work up tram road, gusting over 90kph and building with 2 large shelter belt trees just come down and no Warning from MS for this.
This is what puts people off MS.

http://www.metservice.com/warnings/severe-weather-watch

SEVERE WEATHER WATCH FOR CANTERBURY ISSUED BY METSERVICE AT 0913hrs 03-Nov-2014

NORTHWEST GALES FOR INLAND CANTERBURY

Strong northwesterlies are expected to affect much of the country today and these could rise to severe gale in exposed parts of inland Canterbury.

This watch is for the possibility that northwesterlies could rise to severe gale in exposed parts of inland Canterbury today before easing this evening.

People in this area are advised to keep up to date with the latest forecasts in case this watch is upgraded to a warning.

Rain in Buller, the Tararua Ranges and Mt Taranaki has eased and the watch for heavy rain in these areas is lifted.

Severe gales are no longer expected in Taihape, Hawkes Bay and Wairarapa north of Carterton and the watch for these areas is also lifted.

This Watch will be reviewed by 9pm 3rd November

http://www.metservice.com/rural/canterbury-plains

Fine with strong northwesterlies, gusting 100 km/h in exposed places. A cold southwest change this evening brings showers, some heavy with isolated thunderstorms and hail possible.

This has been a most interesting post and explains this feature of New Zealand weather well. Occasionally a similar situation can develop in the UK to the east of the Pennines and way back in 1962 it had serious consequences for the city of Sheffield:

http://secretsheffield.wordpress.com/20 ... gale-1962/

The following text is from an article by Philip Eden in a newsletter of the Royal Meteorological Society and explains the phenomena as applied to the UK.

"The principal cause of this exceptional gale is known as the "resonant lee wave effect". The airstream covering the British Isles on 16 February 1962 had travelled from the sub-tropical Atlantic, having originated some 1500km southwest of the Azores. It was therefore an unusually warm airflow, although near the Earth's surface it had been cooled by several degrees during its journey across the ocean. This sort of temperature profile suppresses turbulence and the flow of the wind becomes strongly stratified. When such an airflow crosses a mountain range, standing waves are established downwind on the range. You can see similar standing waves in a river, downstream of an obstruction such as a weir. Sheffield lay under a wave-trough with the airflow "squeezed" – and therefore accelerated – between the base of the trough and the ground beneath".

Yes, I am normally in the queue to criticse when the website fails, etc but I have seen nothing wrong in the warnings issued in the past couple of days. People need to remember they are WARNINGS, not fact, and NZ climate is a fickle beast.

I saw extensive severe gales accross the Canterbury High Country driving from the West Coast to ChCh yesterday afternoon, and its also very windy and dusty in ChCh here as I type. So both yesterdays and todays warnings are warranted.

Razor wrote:Yes, I am normally in the queue to criticse when the website fails, etc but I have seen nothing wrong in the warnings issued in the past couple of days. People need to remember they are WARNINGS, not fact, and NZ climate is a fickle beast.

I saw extensive severe gales accross the Canterbury High Country driving from the West Coast to ChCh yesterday afternoon, and its also very windy and dusty in ChCh here as I type. So both yesterdays and todays warnings are warranted.

What was the wind like up in the high country razor?

Simon Culling wrote:This sort of temperature profile suppresses turbulence and the flow of the wind becomes strongly stratified. When such an airflow crosses a mountain range, standing waves are established downwind on the range.

Yesterday there were many pilot reports of severe turbulence in breaking mountain waves across the South Island and lower North Island.

matttbs wrote:

Razor wrote:Yes, I am normally in the queue to criticse when the website fails, etc but I have seen nothing wrong in the warnings issued in the past couple of days. People need to remember they are WARNINGS, not fact, and NZ climate is a fickle beast.

I saw extensive severe gales accross the Canterbury High Country driving from the West Coast to ChCh yesterday afternoon, and its also very windy and dusty in ChCh here as I type. So both yesterdays and todays warnings are warranted.

What was the wind like up in the high country razor?

As per the above (and earleir post) severe gales particulalry between Cass and Springfield, enough to turn lakes pearson and Lyndon into spray laden tempests

Hello Tunster, the flow you have highlighted is related to the airmass as a whole as it approaches the high ground and does not refer to the very turbulent flow on the lee side. It is the hills/mountains that cause the stratified air to form waves and potentially become very turbulent. Pilots would certainly be aware of such conditions.

The NW Gales have died down, now, thank goodness.
Some cloud to the south

NZ Thunderstorm Soc wrote:The NW Gales have died down, now, thank goodness.
Some cloud to the south

I'm just watching that cloud about to go overhead here now: quite an odd yellowish cast to it among the dark grey.

Im picking the MS were cautious as there is a very strong upper level jet which can ramp up the maximum wind speeds, but it was more or so about the high Country I would have picked given the general angle and spacing of isobaric flow. For the east coast its more a 1 in 2-3 years thing when a NWer gets over 110kmh like last year's 11th September event, good ol mad dog NW eh

This was yesterday in Evans Bay, Wellington

http://imgur.com/e36ayOy

Wind stayed all day in Wellington (and points north) but the sun returned early. The forecast was somewhat more pessimistic than the reality regarding any shower activity.