Severe Tropical Cyclone Wilma is now a Cat 4 cyclone says the Joint Typhoon Warning Centre.
Winds are now sustained at almost 215km/h with gusts to 260km/h.
The air pressure is an incredibly low 940hPa.
Wilma is the first cyclone this season to reach Category 4 status.
on 26/01/2011 11:50am
I generally check accuweather.com who have really good data models and long range forecast and this is their prediction for Friday and Saturday. The forecast points to possible local flooding and winds in Auckland on Friday night/ Saturday morning. Also it indicates that the weather should clear out by Saturday evening which tells me this is a fast moving system – Here is the link:
I would be really interested to know how intense this CAT 4 storm will be when it reaches NZ as heavy rain seems imminent though i am not sure about the winds!
on 26/01/2011 10:57am
How often do cyclones of 940hpa category 4 come this close to NZ ? And has there ever been a cyclone hit NZ before at a higher level than Category 1.
on 26/01/2011 11:04am
Hi there – a few have been that strength nearing New Zealand but not many.
Keep in mind Wilma is tracking sideways (east to west) and not downwards (north to south), so the sea temperatures aren’t really dropping yet. Once she turns southerly on Friday she will quickly lose intensity.
This links shows a few: http://en.wikipedia.org/wiki/Category:Tropical_cyclones_in_New_Zealand
A number of cyclones have tracked down towards NZ with Cat 1 winds or higher…. storms lIke Fergus and Drena back in 96/97 for example. Numerous other lows, without names, have passed NZ with cat 1 or 2 strength winds too (and some in the Southern Ocean even higher).
on 27/01/2011 12:06am
I understand its ocean temperatures that develop Cyclones and that they are hard to predict, but what is it that determines their direction? Is it atmospheric pressure? Oceanic temps? What is it that the models analyise to form any sort of a prediction on a cyclones movements?
on 27/01/2011 12:48am
Cyclones are steered by atmospheric prevailing winds – in other words, they go with the flow. If a storm moves slowly the winds are fairly even around the centre. If they move fast then the winds build up on the front of the system but decrease behind it.
You’ll find they’ll often take the path of less resistance in the air pressure. Zelia was helped along by very strong upper level winds which saw her racing towards NZ at over 65km/h. Others move at human walking speed.
Wilma is slowing down now but once she starts to turn SE she will hitch a ride with some upper levels winds and zip off to the south east of us.
Cyclones are often steered by large highs once they reach NZ.
p.s. – this NASA link might be helpful too (it’s a kids page sorry!): http://kids.earth.nasa.gov/archive/hurricane/movement.html