Each year on 23rd March, National Weather Services around the globe celebrate World Meteorological Day. This marks the establishment of the World Meteorological Organization (WMO) on this day in 1950. WMO is the global co-ordinating agency for meteorological and hydrological activities, formed because weather simply doesn’t limit itself to national boundaries. World Meteorological Day is an occasion to commemorate the work that national meteorological and hydrological agencies undertake 24 hours a day, 365 days per year – work that produces weather forecasts and warnings to help keep our communities safe. The recent passage of Cyclone Pam near Vanuatu and past New Zealand are timely reminders of these efforts.
Collecting weather data …
The routine collection of weather data is one part of MetService’s international responsibilities under the Global Observing System (GOS). Worldwide, weather agencies take observations of pressure, temperature, wind and rainfall around the clock. Data come from ships, buoys, weather balloons and land-based weather stations, and are transmitted via the WMO Global Telecommunication System (GTS). This is a world-wide stream of data used as input into global weather forecast models. The better we can “start off” (initialise) the global computer models as to the current state of the atmosphere, the better the future state will be predicted – and the more accurate the weather forecast will be for your place.
In New Zealand alone, hundreds of weather stations from Stewart Island to Cape Reinga tell us how wet, warm, or windy it is every hour, as well as measuring pressure and humidity. Weather balloons are released twice daily at several locations around the country. Recently, MetService has collaborated with the U.K. MetOffice to enable kiwis to share their local weather data on the ‘Your Weather’ section of metservice.com via the ‘Weather Observation Website’ (WOW) system.
… for climate knowledge, too
This year, the theme for World Meteorological Day is ‘climate knowledge for climate action.’ This is a timely focus. Globally, 2014 was the warmest year on record and fourteen of the fifteen hottest years have occurred this century. But how do we know this? That’s right – we looked back at historical weather data.
Think of climate as the sum of all the weather. If you smooth out all of the edges looking at things longer-term (from a climate perspective), it is possible to more clearly understand what is going on. Climate patterns such as the El Nino Southern Oscillation and the Southern Annular Mode are more ‘visible’ this way, including their effect on New Zealand wind, rain and temperature.
‘Reanalysis data’ is a very important tool for scientists trying to unlock the physical mechanisms behind our climate – trying to understand why we had a wet month, a warm year, or an active Cyclone season. Reanalysis datasets input historical weather data from around the globe into the same climate model, and extend it back over time. The relationships found in the past can help us forecast the future – this is the basis of seasonal climate predictions. For example, El Nino springs tend to be very cold in New Zealand, due to frequent southerly airstreams over the country. When we know an El Nino spring is coming, and in the absence of other major climate factors, the odds are that we’re in for an unusually cold spring.
There are many examples of when historical weather data helps put things into climatic context. For example, people have asked, “is Cyclone Pam the worst Tropical Cyclone to hit the South Pacific?”. The answer relies on good data being available. Since Cyclone Zoe (2002) and Cyclone Pam (2015) both reached an estimated minimum central pressure of 890hPa, it looks like a tie. And although satellites provide a relatively short record, their data can also help answer questions about Tropical Cyclone frequency. No increase in Tropical Cyclone numbers has been observed in the South Pacific over the last few decades since reliable satellite data have been available.
MetService also contributes to international climate activities directly. MetService CEO Peter Lennox is New Zealand’s Permanent Representative to the World Meteorological Organization. In addition, MetService has supported several major climate initiatives in New Zealand recently.
MetService and NIWA have collaborated to achieve official Global Climate Observing System (GCOS) Reference Upper Air Network status for the NIWA atmospheric research station at Lauder in Central Otago.
This is only the fourth upper-air site to be certified in the world, and the first in the southern hemisphere. Well-calibrated atmospheric observations are crucial to documenting climate and climate change. The standard network of upper-air meteorological observations, and also weather satellites, provide good coverage – but high-quality observations are needed against which these standard observations can be calibrated. The pairing of Lauder observations and MetService’s Invercargill radiosonde data will achieve the necessary calibration.
And NASA’s super pressure balloon is awaiting lift off at Wanaka, being delayed due to adverse winds associated with Cyclone Pam. Designed to drift eastwards at an altitude of 110,000 feet (‘near space’), NASA expects the super pressure balloon to circumnavigate across South America and then South Africa, on its potentially record-breaking flight. Depending on the stratospheric wind speeds, the balloon should circumnavigate the earth every one to three weeks. The flight goal is to exceed the current super-balloon flight record of 54 days, and to maintain a constant float altitude. If the balloon test is validated, this opens the door for relatively inexpensive atmospheric research. You can track the balloon here.
Best known for the daily forecasts and warnings that help New Zealanders stay ahead of the weather, MetService is also actively engaged in the scientific research that keeps those forecasts at the leading edge of international best practice.
Research presentations at the conference cover topics from the fundamentals of local-scale numerical and dispersion modelling through to its application to real-world problems, such as forecasting the altitude to which snow will fall and which air space is safe and not safe for aviators after a volcanic eruption.
MetService is also at the forefront of operational meteorology, locally and overseas. Conference presentations in this area cover topics such as the expansion of high-tech observing systems and the application of their data to detection of hazards like volcanic eruptions and aircraft icing; case studies of major severe weather events, with a view to the important role that meteorologists have in making the big calls; and New Zealand’s work with meteorological communities in the Southwest Pacific and globally.
In keeping with our national fascination with all things weather, one presentation will also take a look back over the rich history of weather and the meteorological service in New Zealand. Delegates will also visit MetService’s international headquarters at the conclusion of the conference, which is being held close by at Victoria University of Wellington’s Kelburn campus.
In summary, this year’s Meteorological Society conference offers a flavoursome sampling of the depth and breadth of activities recently undertaken by MetService.
Here’s a full run-down of MetService presentations at the conference:
Numerical Weather Prediction and Weather Forecasting – Future prospects
Applications of dual-polarisation weather radar at MetService
A case study of the August 2011 Polar Outbreak
Satellite Diagnosis of Tropical Cyclone Ita before it was named
Keynote: Rebekah LaBar
Storms and Chasing in the USA and Australia
How Low will the Snow go?
The Wellington Volcanic Ash Advisory Centre
Wellington VAAC ash dispersion modelling with HYSPLIT
Don’t lose your mind: A case for conceptual (as well as computer) models (5 minutes)
World Meteorological Organization – What? Why? & Where? (5 minutes)
Detecting aircraft icing from satellite imagery (5 minutes)
iwonderweather – Weather History Website
The Role of SWFDDP in the South Pacific Tropical Cyclone Warning System
MetService Weather Radar Network Expansion Programme
MetService’s newest long-range weather radar, situated near Kaeo in Northland, officially commenced operations on Monday 28 July 2014, with early imagery from the radar enabling MetService forecasters to provide very valuable information to Civil Defence and the public ahead of the June storms experienced in the region.
Although Northland is also covered by MetService’s Auckland radar (on Mt Tamahunga, near Warkworth), by the time that radar’s beam reaches the Far North it is several kilometres above the ground, meaning that a lot of rain quite literally falls ‘under the radar’ and is not accurately detected as a result.
The new Northland radar has an expansive view of the Far North region, which will provide excellent weather detection across a range of 300km from the site. It is the ninth radar in MetService’s network, and the fifth of five new radars installed over the last six years to support expanded thunderstorm warning services. It is a powerful weather forecasting tool providing detailed depiction of torrential rain, hail and snow storms.
MetService worked closely with Te Runanga o Whaingaroa and local marae groups, as well as the Shareholders of the Te Touwai land block on which the radar is built, to gain the support of the local community. Another great outcome of this engagement is an annual scholarship set up by MetService to support local students with an interest in meteorology or related sciences; a MetService meteorologist has also visited schools in the area to talk about weather and the role of the weather radar.
New Zealand’s first modern weather radars were installed over 20 years ago to provide coverage of the Auckland, Wellington and Canterbury regions, followed some time later by a Southland radar. The current project has seen new radars established in Taranaki (2008), the Napier/Gisborne region (2009), Bay of Plenty (2010) and Westland (2011).
Cyclone Lusi crossed the upper South Island overnight and is now pulling away across the open waters of the southern Pacific Ocean.
Lusi brought a period of heavy rain to the Tararua Range, as well as much of the hill country around Nelson and northern Marlborough. Gusts reached 140km/h about the hill tops of Wellington, and 110km/h downtown at the wharf.
Below are the rainfall accumulation maps from 9am Thursday until 9am Monday, in 24 hour steps.
It shows that some of the dry pastures from Waikato to Taihape did not receive much precipitation at all, with 4.5mm at Hamilton. New Plymouth recorded 2.8mm, whilst Mount Taranaki managed over 150mm during the same time.
A summary of observation for the passage of Lusi
Rainfall 60–80mm generally, but Kaikohe received 105mm and PuhiPuhi 101mm.
Winds gusting 139km/h at Cape Reinga, 95km/h at Hokianga and 115km/h at Marsden Point.
Rainfall mostly 25–40mm, but a few stations recorded over 60mm (no warning issued for rain). Winds gusting 113km/h at Whangaparaoa and 90km/h on the Harbour Bridge.
Coromandel and the Bay of Plenty:
Rainfall generally 50–80mm, but 230mm at the Pinnacles and 156mm at Waikura.
Winds gusting 96km/h at Golden Valley and 107km/h at the Mamaku radar.
Waikato, Waitomo and Taranaki:
Mostly 5–15mm, but 131mm at Te Aroha and 133mm at Paeroa as well as 147mm at North Egmont and 169mm at Dawson Falls. Winds were gusting 75km/h at Taupo and 105km/h at Hawera.
Rainfall mostly 20–50mm but 66mm at Ruapehu and 40mm at National Park.
Winds gusting 81km/h at Mangatepopo and 105km/h at Waiouru, but in excess of 180km/h on the Mt Ruapehu ski fields.
Rainfall mostly 20–40mm, but 122mm at Harapara, 142mm at Arowhana and 145mm at Hikuwai.
Rainfallmostly 10–30mm, but 215mm at Parks Peakand 83mm at the Waipoapoa Bridge. Winds gusting 122km/h at Mahia and 125km/h at Castlepoint.
Rainfall 20–30mm, but between 150 and 245mm in the Tararua Range. Winds gusted 100km/h at Paraparaumu and 117km/h on the Rimutaka Hill Road. Both Kelburn and Aotea Wharf gusted 110km/h.
Rainfall mostly 30–70mm, but between 150 and 300mm about the inland hills and ranges, and 134mm at Takaka.
Mostly 20–50mm, but 100–140mm inland and 87mm at Kaikoura.
Rainfall amount mostly 20–40mm , with 38mm at Darfield and 35mm at Christchurch.
However, Akaroa received 80mm and 51mm at Rangiora.
Rainfall amounts 15–30mm about the eastern coastal hills, but a few areas received just in excess of 40mm.
We issued Severe Weather Warnings for Northland, Auckland, Waikato, Coromandel Peninsula, Bay of Plenty/Rotorua, Gisborne, Hawkes Bay, Wairarapa, Wellington, Nelson, Marlborough, Buller, South Canterbury and North Otago. The first warning was issued on Friday morning, the first watch for the event was issued on Wednesday morning, and reference to significant weather first appeared in the Severe Weather Outlook on Sunday afternoon even before Lusi was named as a tropical cyclone.
Here’s a satellite image showing ex-tropical cyclone Lusi lying west of Taranaki this morning.
The resulting tropical airmass it brought a warm start to the day for most over the North Island
Conditions continue to improve over the upper part of the North Island, with a few showers expected there for the remainder of the day.
The image above shows the progression of the rain over the last two days and the expected rainfall over the country until tomorrow morning. Of note is that some data is missing from the middle panel, where rainfall exceeded 200mm in places over the Coromandel. A further 10-20mm is expected for the Christchurch region for the remainder of today, before starting to ease overnight tonight.
As the low crosses over the central parts of New Zealand tonight, strong winds are also expected. Winds around Wellington should increase dramatically this evening as the flow turns from a sheltered and warm northeasterly to a more exposed and much more vigorous northwester. Rain may accumulate to warning amounts for South Canterbury and North Otago. At this stage we are not expecting Christchurch to exceed warnings amounts. Keep up to date with the latest warnings at http://www.metservice.com/warnings/home
Where to from here?
Ex-cyclone Lusi, will continue to move away from New Zealand into the open waters to the southeast of Otago.
Cyclone Lusi continued to push southwards overnight bringing with it strengthening winds and bursts of rainfall. Ahead of the worst of the weather a shield of high cloud spread across the North Island.Gusts of around 130 km/h have so far been recorded at Cape Reinga, closest to the centre of Lusi, but elsewhere across Northland and Auckland gust speeds have been creeping up through the morning, with gusts of almost 90 km/h recorded at sites in the city.
The strong winds and gales are forecast to continue through the day so please stay up to date with all the latest Severe Warnings and Watches
As well as the winds rain is still moving across the country with rainfall totals so far reaching 40 to 60 in many spots in the North of the country. The rain gauge at Paeroa has recorded over 80mm of rain in the 12 hours since midnight. As with the wind there is still some more rain to come and this rain is likely to head onto the South Island overnight and into Sunday.
Where is Lusi going?
The forecast for the rest of the weekend is looking similar to that from yesterday with the centre of Lusi tracking southwards to the west of the country today before sliding the across the top of the South Island on Sunday. The change in direction is likely to bring gales from different directions, bringing the risk to places like Taranaki and Wellington on Sunday.
Here are the latest forecast positions into the start of next week. The thin black lines are isobars which represent lines of equal pressure on the map, like contour lines on a map, where these lines are closest the winds are strongest. Around centres of low pressure in the southern hemisphere winds travel in a clockwise direction, but remember that New Zealand’s rugged terrain plays a large part in local wind speeds and directions
Cyclone Lusi, now a category 2, has moved out of the tropics south of 25S, and is now approaching northern New Zealand.
RSMC Wellington has taken over the reins of Lusi from RSMC Fiji this morning, currently a Category 2 tropical cyclone, and at 5am is lying about 800km north of Cape Reinga. Lusi’s speed of movement is about 35 km/h, and on its current track is expected to pass just to the northwest of North Cape around midday Saturday.
Lusi is showing signs of becoming an extra-tropical system, with cloud shearing away from its centre, but it still contains a lot of energy and severe weather.
MetService has been monitoring this system for several days, and there are severe weather warnings and watches for a number of North and South Island places. As this low passes by the far North, a period of heavy rain and easterly gales is likely from Northland to Gisborne. The upper South Island is also likely to see substantial rainfall from late Saturday into Sunday. Rainfall in Christchurch will be from an easterly direction, and amounts will be modest by warning standards.
MetService will continue to update our blog daily as the storm approaches to highlight the risks to New Zealand. You can view the latest Severe Weather Video update here: http://metservice.com/tv/#severe
Cyclone Lusi now a Category 3 and moving southwards
Cyclone Lusi has intensified into a Category 3 cyclone and is beginning to move southwards toward northern New Zealand. It should pass well east of Norfolk Island.
The image above shows the analysis and satellite picture at 5am on the 13th of March 2014. Tropical Cyclone Lusi is located near the centre of the image. The North Island of New Zealand is showing at the bottom of the image.
On the current track, Lusi is forecast to cross latitude 25 South around midday Friday New Zealand time, moving from the jurisdiction of RSMC (Regional Specialised Meteorological Centre) Fiji into RSMC Wellington’s area of responsibility. You can read more about the RSMC regions and cyclone categories in this blog post: http://blog.metservice.com/2013/10/tropical-cyclone-season-2013-14/
The track map produced by the Fiji Meteorological Service shows Lusi taking a southerly track around 175E.
The expected track of Lusi is slowly becoming more defined, but there are still some subtle yet significant variations in speed and intensity. This can be seen most clearly on the comparison between global models valid for 1pm on Saturday.
The images above show the forecast position of Lusi for 1pm on Saturday (New Zealand time) according to five different computer models.
Ensemble guidance is showing the track to be around, or just to the north of, North Cape before re-curving across the upper South Island. There is increasing agreement between the various modelling centres.
Regardless of the eventual cyclone track, Lusi is expected to bring a period of heavy rain and gale to severe gale winds to many places from Northland to Canterbury. A watch has been issued for this event, and an increasing number of regions will be included as the finer details become clearer. Severe Weather Warnings will be issued on Friday.
Tropical Cyclone Lusi has been moving slowly south-southeast and is currently lying just east of Port Vila where it brought heavy rain and strong gales.
Lusi is expected to intensify to a Cat 3 (winds 119–157 km/h) cyclone Wednesday evening while moving southeast over the open waters of southern Vanuatu and Fiji.
Computer models are still predicting Lusi to move out of the tropics (south of 25?South) on Friday as it moves in a southerly direction towards the upper North Island. At this stage, the cyclone is expected to make landfall somewhere between North Cape and western Bay of Plenty during Saturday or Sunday, before re-curving across New Zealand and moving swiftly out over open waters east of the South Island on Monday. The various computer models are still struggling to agree on its future location and speed of movement, but a track over the upper North Island followed by a path over the upper South Island is currently favoured.
The above images show the Ensemble model guidance produced by UK Met Office of the movement and position of Lusi. The image on the left shows a swathe of possible tracks with colours to distinguish the range of probabilities. The image on the right shows the average track of all the forecast tracks.
As this system moves across New Zealand this weekend, it will bring with it the potential for a period of significant severe weather for most of the North Island and the northern half of the South Island. A burst of intense rain and gales are likely. A Severe Weather Watch has been issued for Northland, Auckland and the Coromandel Peninsula as a heads up. Further Severe Weather Watches and Warnings are likely in the coming days.
As the track of Lusi has the potential to be erratic, the exact distribution of severe weather is likely to change between now and Lusi’s arrival over New Zealand.
Tropical depression 18F was upgraded and named Tropical Cyclone Lusi during the morning of Monday 10th March while lying over northern Vanuatu.
Lusi is currently lying just east of Espiritu Santo and moving very slowly east-southeast. It is expected to intensify to Cat 3 (early hurricane intensity) on Wednesday midway between Vanuatu and Fiji (New Zealand can be seen at the bottom of the picture above). ‘Hadi’ is expected to move northeast towards the southern Solomon Islands.
The track map produced by the Fiji Meteorological Service shows Lusi taking a path with its most damaging effects expected to stay to the west of Fiji.
Currently, computer models are expecting Lusi to leave the tropics (by moving south of 25º South) on Friday before heading in a southerly direction towards the northern half of the North Island. At this stage, the cyclone is expected to landfall over New Zealand somewhere between North Cape and the Bay of Plenty during Saturday or Sunday, before re-curving and moving swiftly out over open waters to the east of the South Island on Monday.
As the cyclone moves across New Zealand this weekend, it will bring with it the potential for significant severe weather from Northland to Canterbury including intense rain, severe gales, large waves and abnormally high tides in many places.
As with all weather systems, there is still a degree of uncertainty about Lusi’s track near New Zealand. This will obviously have a bearing on the exact distribution of severe weather over the country.
Ex-Tropical Cyclone Evan is playing a part in New Zealand’s weather this Christmas.
Now that it has passed across the seas to the north of the North Island, the heaviest of the rain over northern New Zealand is over. This will be the last update of the “Evan” blog.
Update: Tuesday 25 December
Heavy rain in Northland has eased. It’s still raining on and off there, though, as it is over about the northern half of the North Island. A Severe Weather Watch covers the possibility of a few further bands of heavy precipitation rotating around Evan.
Today, afternoon and evening showers and thunderstorms – mostly inland – are part of the weather picture. The action is expected to be from Taranaki through to Wellington and Wairarapa, and in Buller, Nelson, Marlborough and north Canterbury. Keep an eye on the Severe Thunderstorm Outlook; Severe Thunderstorm Watches or Warnings may follow.
On Boxing Day, Evan is expected to lie off to the northwest of Taranaki. At this time it will maintain a flow of very warm moist air over the North Island, and rain or showers are expected in many places. Heavy falls are possible in eastern Bay of Plenty and in thundery showers over high ground. See the Severe Weather Outlook for more detail.
Meanwhile, a southerly change with rain is expected across the South Island on Wednesday. This should cool things off a bit – and lower the humidity.
Where to find important forecast information
Severe Weather Warnings and Severe Weather Watches:
Now that Evan is south of Viti Levu and moving away, this will be the last blog post relaying Fiji Meteorological Service’s Special Weather Bulletin.
Special Weather Bulletin Number THIRTY FOUR FOR FIJI ON SEVERE TROPICAL CYCLONE EVAN ISSUED FROM RSMC NADI at 9:31am on Tuesday the 18th of December 2012 TROPICAL CYCLONE WARNING
A GALE WARNING REMAINS IN FORCE FOR KADAVU, BEQA, VATULELE AND NEARBY SMALLER ISLANDS .
A STRONG WIND WARNING REMAINS IN FORCE FOR THE REST OF FIJI.
A DAMAGING HEAVY SWELL WARNING REMAINS IN FORCE FOR FIJI.
SEVERE TROPICAL CYCLONE EVAN CENTRE [970HPA] CATEGORY 3 WAS LOCATED NEAR 19 DECIMAL 7 SOUTH 177 DECIMAL 2 EAST OR ABOUT 220 KM SOUTH OF NADI OR ABOUT 130 KM SOUTHWEST OF KADAVU OR ABOUT 220 KM SOUTHWEST OF SUVA AT 10:00AM TODAY. THE CYCLONE IS MOVING SOUTH AT ABOUT 14 KM/HR.
CLOSE TO ITS CENTRE THE CYCLONE IS EXPECTED TO HAVE AVERAGE WINDS UP TO 150 KM/HR WITH MOMENTARY GUSTS TO 210 KM/HR.
ON THIS TRACK, THE CYCLONE IS EXPECTED TO BE LOCATED ABOUT 380 KM SOUTH OF NADI OR ABOUT 260 KM SOUTH-SOUTHWEST OF KADAVU OR ABOUT 360 KM SOUTH-SOUTHWEST OF SUVA AT 10:00PM TODAY AND 375 KM SOUTH-SOUTHWEST OF KADAVU OR 475 KM SOUTH-SOUTHWEST OF SUVA AT 10:00AM TOMORROW.
DESTRUCTIVE WINDS MAY BEGIN SEVERAL HOURS BEFORE THE CYCLONE CENTRE PASSES OVERHEAD OR NEARBY.
FOR KADAVU, BEQA, VATULELE AND NEARBY SMALLER ISLANDS:
DAMAGING GALE FORCE WINDS WITH AVERAGE SPEEDS UP TO 85 KM/HR AND MOMENTARY GUSTS TO 110 KM/HR. PERIODS OF HEAVY RAIN WITH SQUALLY THUNDERSTORMS WITH FLOODING OF LOW LYING AREAS. DAMAGING HEAVY SWELLS WITH SEA FLOODING OF LOW LYING COASTAL AREAS.
FOR THE REST OF FIJI:
STRONG WINDS WITH AVERAGE SPEEDS TO 55 KM/HR AND MOMENTARY GUSTS TO 85 KM/HR. PERIODS OF RAIN, HEAVY AT TIMES AND SQUALLY THUNDERSTORMS.
FLOODING INCLUDING SEA FLOODING OF LOW LYING COASTAL AREAS.
The following information is provided especially for the mariners:
HURRICANE FORCE WINDS AND PHENOMENAL SEAS NEAR THE CYCLONE CENTRE. STORM FORCE WINDS WITHIN 30 NAUTICAL MILES OF CENTRE AND VERY HIGH SEAS. GALE FORCE WINDS AND HIGH SEAS TO ABOUT 100 NAUTICAL MILES FROM CENTRE. ELSEWHERE, STRONG WINDS AND ROUGH TO VERY ROUGH SEAS. HEAVY SWELLS.
The next Special Weather Bulletin for Fiji on Severe Tropical Cyclone Evan will be issued at or around 12:30PM today.