Cyclone Hola hits: Heavy rain, wind gust warnings

Author: NZ Herald,
Publish Date: Mon, 12 Mar 2018, 5:38AM

Heavy rain has started falling in the Far North, as ex-tropical cyclone Hola begins its strike on New Zealand - but there is hope for many residents, with predictions the storm will peter out by tomorrow.

MetService meteorologist Arno Dyason said the eye of Hola was still to the north of New Zealand, but Northland was beginning to see some of the effects.

"At this stage nothing too significant is happening, but watch this space as it is meant to really kick in later this morning."

Wind gusts of between 100 to 130km/h are expected in exposed places as the weakening cyclone slides down the northeastern side of the upper North Island today.

Downpours of 100 to 150mm are forecast today in Northland and to 3am tomorrow around Gisborne, and up to 130mm on Great Barrier Island by 11pm tonight.

WeatherWatch NZ said Hola would also bring a significant storm surge with "extremely dangerous" seas and coastal conditions.

There were currently 9m waves out at sea, and once it reached New Zealand there could be 4 to 6m swells near eastern Northland and East Cape.

Hola - the third major storm to strike the country this year - is forecast to be gone by early tomorrow.

"The low is expected to track to the northeast of the North Island, with the strongest winds and rainfall in the southern quadrant, affecting Northland, Auckland, Great Barrier Island, Coromandel and Gisborne," Dyason said.

"But there is still some uncertainty about its exact effects."

It is expected to be out to sea off the East Cape by midnight, and mostly gone by tomorrow morning.

The MetService's rain radar, at 5am Monday, shows light to heavy rain starting to fall at the very northern part of New Zealand, including Cape Reinga.

Look at the increased agreement of the central position of Hola tomorrow night in the model run today compared to yesterday (see the smaller cluster of L's in the latest model run to the left). Want to understand more about ensemble forecasting? https://t.co/zFywevYPEx ^AC pic.twitter.com/sRZgVHC4dq
— MetService (@MetService) March 11, 2018

WeatherWatch head analyst Philip Duncan said Hola had today begun the transition from a "tropical" cyclone (with a warm core) to an "extra-tropical" cyclone (with a cold core).

This process "stretched out", spreading the energy further afield and reducing peak winds.

It would still bring a small but very "potent burst'' of rain our way.

"Best estimates is that this torrential rain will brush Northland, potentially Coromandel Peninsula, but could be most intense through Bay of Plenty and into the Gisborne and northern Hawke's Bay ranges,'' Duncan said.

"This rain may cause flooding and slips in these areas and affect state highways."

It is also thought that winds in the system will change a lot during its time here with potential for wind tunnels to form.

"Wind damage may be in certain areas rather than widespread, with various wind tunnels being one factor and the other factor being the damaging winds right at the centre of [a new] low.

#UPDATE: Full details about how #CycloneHola may impact #NewZealand across Monday (+12 Maps) https://t.co/yzPCoDbhlU via @weatherwatchnz #weather #hola #storm
— WeatherWatch.co.nz (@WeatherWatchNZ) March 11, 2018

Surface flooding and slips are also possible, the MetService warns, so motorists are encouraged to be aware of potentially hazardous conditions.

Meanwhile, Vector said it had crews on standby in case the cyclone did any damage to the electricity network.

Chief network officer Andrew Botha said teams were ready to head out as soon as it was safe to do so should any lines came down because of stormy conditions.

Botha urged people to tie down things like trampolines and outside furniture which may be thrown around in the storm.

"And please, always treat downed lines as live and stay well clear.''

"But these winds will only cause damage near the centre. So if the centre remains out at sea, so too will the worst of the winds."

The impact of a storm surge would also depend on how far out to sea the centre was.

"Coastal erosion and damage is likely in some areas, especially when - or if - the peak winds, high tide and the centre of the low combine in one place at the same time," Duncan said.

"For now, that doesn't appear to be the case but seas and coastal conditions will be extremely dangerous in some eastern and northern faces beaches/marine areas on Monday in the upper and eastern North Island."

The MetService said the latest models predicted Hola moving swiftly and skirting the north east of the North Island today; bringing severe weather to eastern parts of the upper North Island.

There are severe weather warnings and watches in place.

Heavy rain warnings have been issued for Northland, Great Barrier Island, Coromandel Peninsula and Gisborne.

Strong wind warnings are in place for Northland, Great Barrier Island, Coromandel Peninsula, Auckland, Bay of Plenty, Rotorua and Gisborne.

The MetService is warning people in these areas to monitor weather updates, as heavy rain could cause streams and rivers to rise rapidly.

Surface flooding and slips are also possible, the MetService warns, so motorists are encouraged to be aware of potentially hazardous conditions.

Meanwhile, Vector said it had crews on standby in case the cyclone did any damage to the electricity network.

Chief network officer Andrew Botha said teams were ready to head out as soon as it was safe to do so should any lines came down because of stormy conditions.

Botha urged people to tie down things like trampolines and outside furniture which may be thrown around in the storm.

"And please, always treat downed lines as live and stay well clear."

While the northeast will be wet and windy, most of the rest of the country is in for a fine day.

"Wellington is in for a really nice day, and so too Christchurch," Dyason said.

"Most of the South Island should be in for fine weather today, with just a few showers in the far south and on the West Coast."

HEAVY RAIN WARNING:
Northland
Valid: 17 hours from 4am to 9pm Monday
Forecast: Rain is expected to become heavy in the early hours of Monday morning, then ease Monday evening. Expect 100 to 150mm to accumulate in the north and east, but 70 to 90mm elsewhere during this time. Peak intensities of 20 to 30mm per hour.

Great Barrier Island, Coromandel Peninsula
Valid: 14 hours from 9am to 11pm Monday
Forecast: Rain developing Monday morning, with heavy falls, then easing Monday night. Expect 80 to 100mm to accumulate, but 100 to 130mm for Great Barrier Island during this time. Peak intensities of 20 to 30mm per hour.

GisborneValid: 16 hours from 11am Monday to 3am Tuesday
Forecast: Rain is expected to develop around midday Monday with heavy falls and thunderstorms, then to ease overnight Monday. Expect 100 to 150mm of rain to accumulate north of the city, especially about the ranges, and 70 to 100mm further south during this time. Peak intensities of 25 to 40mm per hour in the north.

STRONG WIND WARNING:
Northland
Valid: 14 hours from 6am to 8pm Monday
Forecast: Gale southeasterlies developing around dawn Monday, then turning gale southwesterly around midday Monday, with severe gales gusting 120km/h in exposed places. Winds easing Monday evening.

Great Barrier Island, Coromandel Peninsula
Valid: 16 hours from 11am Monday to 3am Tuesday
Forecast: Gale southeasterlies developing late Monday morning, then turning gale southwesterly Monday evening, with severe gales gusting 130km/h or more in exposed places. Winds easing overnight Monday.

Auckland excluding Great Barrier Island
Valid: 12 hours from 3pm Monday to 3am Tuesday
Forecast: Gale south or southeast winds developing Monday afternoon, then changing gale southwesterly Monday evening, with severe gales gusting 120km/h in exposed places. Winds easing overnight Monday.

Bay Of Plenty, Rotorua
Valid: 13 hours from 5pm Monday to 6am Tuesday
Forecast: Gale southeasterlies developing late Monday afternoon, then turning gale southwesterly overnight Monday, with severe gales gusting 120 to 130km/h in exposed places. Winds easing around dawn Tuesday.

Gisborne
Valid: 16 hours from 5pm Monday to 9am Tuesday
Forecast: Gale southeasterlies developing late Monday afternoon, then turning gale south to southwesterly overnight Monday, with severe gales gusting 120km/h in exposed places, especially north of the city. Winds easing Tuesday morning.

HEAVY RAIN WATCH
Auckland excluding Great Barrier Island
Valid: 12 hours from 9am to 9pm Monday
Forecast: Rain is expected to develop Monday morning, with some heavy falls, then ease Monday evening. Rainfall accumulations may reach short duration warning amounts (eg. 60mm in 9 hours).

Waikato, Bay Of Plenty west of Te Puke and the eastern ranges
Valid: 14 hours from 9am to 11pm Monday
Forecast: Rain is expected to develop Monday morning, with some heavy falls, then ease Monday night. Rainfall accumulations may reach short duration warning amounts (eg. 60mm in 9 hours).

Hawke's Bay north of Hastings
Valid: 12 hours from 4pm Monday to 4am Tuesday
Forecast: Rain is expected to develop Monday afternoon, with some heavy falls, then ease overnight Monday. Rainfall accumulations may reach short duration warning amounts during this time (eg. 70mm in 12 hours).

STRONG WIND WATCH
Waikato
Valid: 13 hours from 5pm Monday to 6am Tuesday
Forecast: Gale southeasterlies developing Monday afternoon, then turning southwesterly overnight Monday, and winds may rise to severe gale strength in exposed places at times until around dawn Tuesday.

Taupo, Hawke's Bay from Hastings northwards
Valid: 11 hours from 7pm Monday to 6am Tuesday
Forecast: Gale southeasterlies developing Monday evening, may rise to severe gale strength in exposed places, then turning southwesterly in the early hours of Tuesday morning and winds gradually easing.

TODAY'S WEATHER
• Whangarei

Rain with heavy falls, easing to showers this evening. Strong southerlies, gusting 90km / h. 23C high, 16C overnight.

• Auckland

Rain developing morning with heavy falls, easing tonight. Strong southeast turning gale southwest, gusting 100km / h from afternoon. 19C high, 17C overnight.

• Hamilton

Rain developing morning with heavy falls, easing tonight. Strong southeasterly turning southwest evening. 19C high, 14C overnight.

• Tauranga

Rain developing morning with heavy falls, easing tonight. Strong southeasterly, possibly gale, turning southwest evening. 21C high, 16C overnight.

• New Plymouth

Cloud increasing morning, then rain at times from afternoon. Southeasterlies strengthening. 21C high, 15C overnight.

• Napier

Rain developing this afternoon. Easterlies turning strong southerly this evening. 20C high,
15C overnight.

• Wellington

Fine with increasing high cloud. Northerlies. 20C high, 14C overnight.

• Nelson

Fine with high cloud. Light winds. 21C high, 14C overnight.