TC Pam Summary

CHRIS NOBLE, MANAGER PUBLIC WEATHER SERVICES

Now that Cyclone Pam has passed the Chatham Islands, here’s a look back at events of the last couple of weeks…

History

Tropical Cyclone Pam began life as a tropical disturbance north of Vanuatu, officially numbered “TD11F” on the 6th March by RSMC Nadi in Fiji.  Over the following days the system slowly strengthened, reaching tropical depression status on 8th March, and following further intensification was named as Tropical Cyclone Pam at 7pm NZDT on 9th March.  Initial forecast tracks suggested TC Pam would continue to intensify and pass between Vanuatu and Fiji, before moving out of the tropics and southeast towards East Cape, New Zealand.

TC Pam strengthened quickly and eventually moved directly across the southern islands of Vanuatu during Fri 13th and Sat 14th March as a powerful category 5 cyclone, causing widespread destruction on some islands, as well as sadly leading to a number of fatalities.  At its peak, just south of Vanuatu, the central pressure reached 896hPa at 1pm NZDT on 14th March, with sustained winds of 250km/h near the centre of the system, making Pam one of the most intense and deadly cyclones on record in the South Pacific.

A microwave image of Severe Tropical Cyclone Pam soon after its peak intensity and crossing Vanuatu on Saturday 14th March. This type of imagery provides a unique view of the structure of cyclone by looking through the cold cirrus clouds and into the convective rainbands spiralling around the centre.
A microwave image of Severe Tropical Cyclone Pam soon after its peak intensity and crossing Vanuatu on Saturday 14th March. This type of imagery provides a unique view of the structure of cyclone by looking through the cold cirrus clouds and into the convective rainbands spiralling around the centre.

 

TC Pam Track Map

The full track for Tropical Cyclone Pam, through to 1am this morning (Wednesday 18th March), is shown below. Times in this image are in UTC (add 13 hours for NZDT).

2015-03-17-1200-tc-pam-track

 

 

Initial MetService commentary and forecasts for New Zealand

On Monday 9th March, before TC Pam was named, MetService meteorologists began regular issues of both press releases and blog entries to keep New Zealanders up to date with the latest official advice.

By Wed 11th March, two days before TC Pam moved across Vanuatu, the following Severe Weather Outlook was issued, focusing on the potential for adverse weather in the northeast of the North Island:

The Severe Weather Outlook issued at 2:34pm on Wednesday 11th March.
The Severe Weather Outlook issued at 2:34pm on Wednesday 11th March.

At this early stage, TC Pam was expected to track southeast from the Tropics and offshore from the North Island, although computer models differed somewhat in how close Pam would pass to East Cape.  For example, here’s the snapshot of a selection of global models posted to the MetService blog on the Wed 11th looking at the forecast position of the centre for 1am Monday 16th March:

Pic3

As you can see above, some models initially expected the centre to pass close to East Cape, while others took a track further offshore.

By Thursday 12th March, the day before TC Pam moved onto Vanuatu, the forecast track in the global models was becoming more certain and the following track map was issued late afternoon. It showed the centre passing offshore from East Cape, with the range of possible tracks including the centre crossing the northeast of the North Island:

Forecast path of cyclone Pam

 

First Severe Weather Watches and Warnings for NZ

As model forecasts converged and the track for TC Pam became clearer, the first Severe Weather Watch was issued at 9:52am on Friday 13th March for gales and heavy rain starting from Sunday night. This Watch included gales affecting Northland, Coromandel Peninsula, Great Barrier Island, eastern Bay of Plenty and Gisborne, and heavy rain affecting eastern Northland, Coromandel Peninsula, Gisborne and northern Hawkes Bay.  An updated Watch on Friday afternoon also highlighted the threat of dangerous wave conditions affecting eastern coasts of the North Island starting near Cape Reinga and eventually spreading as far south as the Wairarapa.

The following morning (Saturday 14th March), at 9:13am, the first Severe Weather Warning was issued alerting to heavy rain in Gisborne, northern Hawkes Bay and the ranges of eastern Bay of Plenty, and severe gales affecting Bay of Plenty (east of Edgecumbe) and Gisborne.  Subsequent warnings issued Saturday evening and on Sunday added eastern Northland and Coromandel Peninsula to the heavy rain warning, and eastern Northland, Great Barrier Island and Coromandel Peninsula to the strong wind warning.

 

Oceanic Warning handover from Fiji to New Zealand

As with all tropical cyclones moving out of the tropics and crossing latitude 25S, official warning responsibility passes from RSMC (Regional Specialised Meteorological Centre) Nadi in Fiji to the Wellington Tropical Cyclone Warning Centre in New Zealand.  For TC Pam, this happened in the early hours of Sunday morning (the 15th) with Nadi issuing their last high seas warning at 1am on Sunday, followed by Wellington issuing at 7am Sunday. The hand-over process requires careful co-ordination between the forecasting centres in Nadi and Wellington.

 

Re-classification

As Pam moved over colder oceans and into stronger upper level winds in the atmosphere, its structure changed.  Tropical cyclones in the Tropics are “warm-cored” in nature and have a near vertical structure, but as they move into the mid-latitudes strong upper level winds help “shear” the circulation, moving the supporting convection away from the storm’s centre and allowing colder air to wrap into the system. This process is called extra-tropical transition, and when it occurs, the responsible warning centre “reclassifies” the cyclone.  Note however, this does not necessarily mean that weather conditions improve.  Instead, the cyclone can, and did, remain very powerful and gales and heavy rain can spread further from the centre affecting a wider area.

 

Impacts on New Zealand

As TC Pam approached northern New Zealand, rain set in over the Far North during Sunday morning while winds over the upper North Island steadily increased.

The period from Sunday morning to Tuesday morning captures the main rainfall over the North Island associated with the passage of TC Pam to the east.  The following maps show the 24 hour accumulations from Sunday morning to Monday morning and from Monday morning to Tuesday morning respectively:

24-hour-rain-maps

Peak wind gusts recorded at MetService North Island weather stations were:

Kaeo Radar: 148km/h Sunday evening
Channel Island: 144km/h Sunday night
Hicks Bay: 144km/h Monday afternoon

The pressure trace at Hicks Bay (closest North Island weather station to the track of Pam) shows how the pressure there responded to the approach and passage of Pam with a lowest pressure of 974.7hPa at midday on Monday:

hix-pressure
This graph covers the 72 hour period from 1pm Sat 14th to 1pm Tuesday 17th March.

As well as wind and rain, very large seas were expected to affect eastern coasts of the North Island.  Surfers in Mt Maunganui commented that the swells were some of the largest they had witnessed while roads around East Cape were inundated by debris as highlighted in the following photos:

In summary, here’s the event records:

tc-pam-stats

 

 

Warning Verification

As with all Severe Weather Warnings issued by MetService, warnings for this event were logged and verified. The following images highlight the areas covered by warnings with a selection of observations:

rain-verification

wind-verification

 

Final words…

Pam has now passed the Chatham Islands and is moving away to the east over the Pacific Ocean as an intense extra-tropical cyclone. Conditions on the Chatham Islands should gradually ease as detailed in the recent Strong Wind Advisory, while an Oceanic Storm Warning remains in force for the system over the Pacific.

During this event, in addition to the numerous regular forecasts produced daily, MetService meteorologists published frequent blog posts, press releases and briefing statements for our clients across all sectors in New Zealand including emergency managers, various media agencies both locally and internationally, along with the general public. MetService.com set a new record for visitor numbers on Sunday 15th March – exceeding stats from TC Lusi one year ago in March 2014.

While New Zealand largely escaped the wrath of Pam, the same cannot be said for Vanuatu. Please spare a thought for our neighbours to the north as the disaster relief effort there continues. A number of aid agencies are appealing for donations including:

New Zealand Red Cross

Unicef New Zealand

Oxfam New Zealand

Save the Children New Zealand

 

Tropical Cyclone Pam Updates – Saturday 14 March 2015

Updated Saturday 14 March 2015 11 pm

BILL SINGH, METSERVICE METEOROLOGIST

Severe Tropical Cyclone Pam was located about 400km east of Noumea, New Caledonia at 7 pm Saturday evening. The cyclone is moving south-southeast at about 25km/hr, away from Vanuatu and New Caledonia. The visible satellite imagery at 7pm shows tropical cyclone (TC) Pam still has an eye, indicating hurricane force winds close to the centre. TC Pam is a Category 5 cyclone with 230 km/hr winds close to the centre. On its current track, the system is expected to move south of 25S, into MetService area of responsibility by 7 am this morning (Sunday, 15th March) and continue to weaken.

Visible imagery at 7 pm
Visible imagery at 7 pm
TC Pam track map issued by RSMC Nadi issued at 9pm
TC Pam track map issued by RSMC Nadi issued at 9pm

TC Pam is expected to have a large impact on New Zealand weather as it heads towards the southeast. The centre of TC Pam is expected to be located about 550 km northeast of Auckland early Sunday evening and about 150 km east of East Cape around midday Monday, 16th March. Image below shows a good agreement with the positons of TC Pam from 3 weather models (UK, ECMWF and GFS) during Sunday and Monday.

Position of TC Pam from three global models
Position of TC Pam from three global models

What happens when a cyclone moves south of 25S?

MetService will take responsibility from Fiji once TC Pam crosses south of 25S (from 7 am Sunday morning) and will issue all tropical cyclone warnings for the cyclone.

A tropical cyclone gets its energy from warm tropical oceans, and once it moves over cooler waters, the structure of the cyclone gradually changes. The eye which is clearly visible now would get filled by upper clouds as the height of the tropopause lowers. The intensity of the cyclone will gradually weaken as wind shear over the system increases, however the maximum winds around the centre are still expected to be of hurricane intensity north of 35S. The area of gales is expected to become larger than its current size to conserve momentum. At this stage, TC Pam is expected to remain warm cored (a signature of all tropical cyclones) till around 35S, then cooler air is expected to intrude the system as it moves towards 40S.

Impact of TC Pam on New Zealand

TC Pam is expected to have a large impact on New Zealand weather, bringing heavy rain and gale force winds to parts of the North Island. The latest warnings and watches for New Zealand can be found here . A warning for heavy rain has been issued for Gisborne, Hawkes Bay and the ranges of Eastern Bay of Plenty. A warning for severe gales has been issued for Great Barrier Island, Coromandel Peninsula, Eastern Northland, Gisborne and eastern areas of Bay of Plenty.

Watches for severe gales have been issued for a broader area including the remaining parts of Northland, northern part of Auckland and northern Hawkes Bay. A watch for heavy rain has been issued for Eastern Northland and Coromandel including Great Barrier Island. The watch is also an alert for dangerous coastal conditions over the east coast of the North Island from Cape Reinga to Wairarapa.

Cyclone Pam is expected to bring heavy swells and very large waves to eastern coastal areas of North Island. The image below shows at least 7 metre waves affecting eastern coastal areas, starting near Cape Reinga during Sunday evening then spreading to Gisborne coastal areas during Monday morning.

Combined Waves during Sunday evening and Monday morning
Combined Waves during Sunday evening and Monday morning

The next update will be issued by 6 am Sunday 15 March.

Update Saturday 14 March 2015 5pm

DAVID MILLER, METSERVICE METEOROLOGIST

As at 4pm today, severe tropical cyclone Pam was located about 200 nautical miles south of Port Vila and about 200 nautical miles east of Noumea in New Caledonia. The Tropical cyclone is then expected to move southeast over the next couple of days. Refer to the latest TC track map issued by RSMC Nadi at 2:18pm today.

Latest infrared satellite image at 4pm local time, showing the position of severe TC Pam.
Latest infrared satellite image at 4pm local time, showing the position of severe TC Pam.

 

 

Latest TC forecast track map issued by RSMC Nadi at 2:18pm.
Latest TC forecast track map issued by RSMC Nadi at 2:18pm.

 

Once the eye of Pam moves south past 25S, Metservice takes over responsibility of issuing Tropical Cyclone Bulletins and associated warnings from RSMC Nadi. The diagram below shows the areas of responsibility for tropical cyclones. At this stage, Pam is expected to cross 25S around 7am tomorrow morning (Sunday).

 

Tropical cyclone warning centres area of responsibility.
Tropical cyclone warning centres area of responsibility.

As well as issuing warnings over land, Metservice routinely issues high seas forecasts within our area of responsibility. These bulletins describe areas of strong winds, heavy swells, and areas of poor visibility, and refer to warnings in the area. You can find a link to the subtropics bulletin here http://www.metservice.com/marine-surf/high-seas/subtropic.

Aviation forecasters will also be busy issuing warnings for the aviation industry known as Sigmets (short for Significant Meteorological conditions). These warnings are written in standardised code for ease of use around the world.

The latest warnings and watches for New Zealand can be found here www.metservice.com/warnings/home . Cyclone Pam is expected to have a large impact in New Zealand. A warning for heavy rain has been issued for Gisborne, the northern Hawkes Bay ranges and the ranges of Eastern Bay of Plenty. A warning for severe gales has been issued for the Bay of Plenty, especially in the east and for Gisborne. Watches for severe gales have been issued for a broader area including Northland, Coromandel, Great Barrier Island and northern Hawkes Bay. A watch for heavy rain has been issued for Eastern Northland and Coromandel including Great Barrier Island, and Hawkes Bay (except northern Hawkes Bay where a Warning is in force). The watch is also an alert for dangerous coastal conditions over the east coast of the North Island from Cape Reinga to Wairarapa.

Note that sea conditions are expected to become extremely dangerous on the north and east coasts of the North Island. This is a map showing swell height in metres at midday on Monday. This swell is exceptionally large, especially in Gisborne and the Bay of Plenty where it could be about 7 metres. This is likely to lead to widespread coastal erosion. Anyone considering venturing near or into the water should take extra precautions and be sure to check the latest forecasts for expected dangerous conditions.

Swell forecast from the ECMWF for noon on Monday, height in metres.
Swell forecast from the ECMWF for noon on Monday, height in metres.

The next update will be issued by 11pm.

 

Update Saturday 14th March at 10:00am

HORDUR THORDARSON, METSERVICE METEOROLOGIST

Tropical cyclone Pam has been severely affecting Vanuatu this morning with the centre passing just east of the capital city, Port Vila on the island Efate. From there it has moved south-southeast to the islands Erromango and Tanna. It is expected to lie just south of Tanna at noon today. This is one of the most intense storms on record with a central pressure estimated at near 890 hectoPascals and sustained winds of around 250 kilometres per hour near the centre. Winds of this strength have the potential to cause catastrophic damage with dangerous flying debris and structural destruction.

caption

Infra red image from 7:32am this morning:

 

For imagery showing an animation of the eye of the cyclone please use this link:

http://tropic.ssec.wisc.edu/real-time/mimic-tc/2015_17P/webManager/basicGifDisplay48.html

 

Caption

A snapshot from the animation, showing the tropical cyclone early this morning as the centre passed just east of Efate in Vanuatu, on course towards the islands to the south-southeast

South of Vanuatu,Severe Tropical Cyclone Pam should be affected by a north-westerly flow at upper levels. This flow should steer Pam onto a south-easterly track that should bring it into the area northeast of New Zealand on Sunday. There is still some uncertainty with respect to the track, so people are advised to keep up with the latest forecasts, watches and warnings on our webpage, www.metservice.com.

Cyclone Pam is expected to have a large impact in New Zealand. A warning for heavy rain has been issued for Gisborne, the northern Hawkes Bay ranges and the ranges of Eastern Bay of Plenty. A warning for severe gales has been issued for the Bay of Plenty, especially in the east and for Gisborne. Watches for severe gales have been issued for a broader area including Northland, Coromandel, Great Barrier Island and northern Hawkes Bay. A watch for heavy rain has been issued for Eastern Northland and Coromandel including Great Barrier Island. The watch is also an alert for dangerous coastal conditions over the east coast of the North Island from Cape Reinga to Wairarapa.

Note that sea conditions are expected to become extremely dangerous on the north and east coasts of the North Island. This is a map showing swell height in metres at midday on Monday. This swell is exceptionally large, especially in Gisborne and the Bay of Plenty where it could be about 7 metres. This is likely to lead to widespread coastal erosion. Anyone considering venturing near or into the water should take extra precautions and be sure to check the latest forecasts for expected dangerous conditions.

caption
Swell forecast from the ECMWF for noon on Monday, height in metres.

 

Update Saturday 14th March at 5.00am

MATTHEW FORD, METSERVICE METEOROLOGIST

Infrared satellite image of TC Pam 3.44am Sat 14th March 2015
Infrared satellite image of TC Pam 3.44am Sat 14th March 2015

At 1am this morning (NZ local time) severe tropical cyclone Pam was located about 70km east of Port Vila, Vanuatu. TC Pam is still a category 5 cyclone, and has intensified slightly overnight with the central pressure dropping to an estimated 899hPa and winds close to the centre of about 250km/h. The area of gales (65km/h winds) is estimated to extend up to 380km from the centre of the cyclone, affecting much of Vanuatu. TC Pam is still moving slowly south, and is expected to cross the southern Vanuatu islands of Erromango and Tanna during the next 12 hours while intensifying slightly.

The above image is an infrared satellite picture of TC Pam taken at 3.44am this morning. Infrared images are colour coded to show the temperature of the cloud tops, which may extend high up into the atmosphere. The eye of the tropical cyclone is the light coloured dot in the middle surrounded by the dark blue (cloud tops of about -82C). What this image shows is the intensely cold cloud tops of thunderstorms surrounding the relatively warm eye of the tropical cyclone. This temperature contrast is one of the ways forecasters can estimate the intensity of a tropical cyclone from satellite imagery.

The latest forecast track map for TC PAM was issued by RSMC Nadi, Fiji at 2.24am this morning. The map shows that TC PAM is expected to take a southeast track to the northeast of New Zealand over the next couple of days. Although the map shows that the category of the system will change as it approaches New Zealand, decreasing from 5 at the moment to 1 south of 30S, this just reflects the fact that the system is moving out of the tropics and is losing its tropical character. The cyclone will remain a very intense storm, with heavy rain, severe gales and high seas associated with it. Please refer to the latest severe weather watches and warnings issued by MetService for more information on its possible impact on New Zealand’s weather.

TC Pam track map issued by RSMC Nadi 2.24am 14th March 2015
TC Pam track map issued by RSMC Nadi 2.24am 14th March 2015

 

Sources:

Fiji Meteorological Service / RSMC Nadi Tropical Cyclone Warning Centre

MTSAT satellite imagery courtesy of Japan Meteorological agency

 

 

 

Tropical Cyclone Pam Updates – Friday 13 March 2015

Update Friday 13th March at 7:00pm

FRANCES RUSSELL, METSERVICE METEOROLOGIST

Satellite picture for the Tropics at 7pm NZDT 13th March
Satellite picture for the Tropics at 7pm NZDT 13th March

Confidence continues to grow in the projected path for Severe Tropical Cyclone Pam. There is currently a Severe weather watch in force, http://www.metservice.com/warnings/severe-weather-watch. Watches and Warnings will continue to be added and updated on our website and this is the first place that they will appear. Meanwhile, The Ministry of Civil Defence and Emergency Management are encouraging those in possibly affected areas to head on over to http://getthru.govt.nz/disasters/storms/ for more information.

What can we expect as TC Pam moves towards New Zealand?

The forecast shows TC Pam is expected to decay to Category 4 once it moves south of New Caledonia, but models show it will have remarkable persistence as it travels on towards New Zealand. MetService has issued a Severe Weather Watch for northern and eastern parts of the North Island. This covers the period when the storm tracks to the east of the North Island during Monday and Tuesday and highlights the risk of severe gales and heavy rain and large seas.
Large waves, as well as storm surge, are likely to have a significant effect as the cyclone passes by New Zealand. Very large, long period waves are likely from Cape Reinga to East Cape on Sunday and Monday, extending south to include Gisborne to the Kaikoura Coast on Monday and Tuesday. Waves of this size have significant potential for coastal erosion, especially combined with gales and storm surge.

How is TC Pam affecting the Pacific right now?

TC Pam is currently Category 5 located 120km northnortheast of Port Vila and 100km eastsoutheast of Lamp, Vanuatu, tracking southsouthwest over Vanuatu, where a Tropical Cyclone Warning is in place for destructive winds, torrential rain and phenomenal seas today and Saturday morning before things ease. The red rings around TC Pam indicate areas of destructive storm force winds and very destructive hurricane force winds. Wind speeds near the centre are currently 240km/h and the area of gales around the storm extends out greater than 300km. In the last 6 hours from 1pm Pekoa Aiport on the island of Espiritu Santo in Vanuatu recorded 107 mm of rainfall.

The latest forecast track map from RSMC Fiji, 1423 NZDT  Friday 13 March 2015.
The latest forecast track map from RSMC Fiji, 1423 NZDT Friday 13 March 2015.

The next update to this blog will be around 6am Saturday 14 March.

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Update Friday 13th March at 1:00pm

ROB KERR, METSERVICE METEOROLOGIST

Satellite picture for the Tropics at 1pm NZDT 13th March
Satellite picture for the Tropics at 1pm NZDT 13th March

Confidence continues to grow in the projected path for Severe Tropical Cyclone Pam and MetService has issued a Severe Weather Watch for northern and eastern parts of the North Island. This covers the period when the storm tracks to the east of the North Island during Monday and Tuesday and highlights the risk of severe gales and heavy rain. Watches and Warnings will continue to be added and updated on our warnings page and this is the first place that they will appear (you can sign up here to receive them by email, another great way to stay right up to date). Meanwhile, The Ministry of Civil Defence and Emergency Management are encouraging those in possibly affected areas to head on over to http://getthru.govt.nz/disasters/storms/ for more information.

What can we expect as TC Pam moves towards New Zealand?

The forecast shows TC Pam is expected to decay to Category 4 once it moves south of New Caledonia, but models show it will have remarkable persistence as it travels on towards New Zealand. These two images show the output from the various models for 1pm Monday afternoon and 1am Tuesday morning.

1pm Monday:

An updated selection of different global models showing mean sea level pressure for 1pm NZDT on Monday 16th March. Pressures lower than 1000hPa have been coloured blue.
An updated selection of different global models showing mean sea level pressure for 1pm NZDT on Monday 16th March. Pressures lower than 1000hPa have been coloured blue.

1am Tuesday:

An updated selection of different global models showing mean sea level pressure for 1am NZDT on Tuesday 17th March. Pressures lower than 1000hPa have been coloured blue.
An updated selection of different global models showing mean sea level pressure for 1am NZDT on Tuesday 17th March. Pressures lower than 1000hPa have been coloured blue.

Whilst there is still a little variation in the timing of its passage, the path of the storm shows excellent consistency across all these models.

How is TC Pam affecting the Pacific right now?

Meanwhile, TC Pam is currently tracking southwards and affecting Vanuatu, where a Tropical Cyclone Warning is in place for destructive winds, torrential rain and phenomenal seas today and Saturday morning before things ease. The red rings around TC Pam indicate areas of destructive storm force winds and very destructive hurricane force winds. Wind speeds near the centre are currently 220km/h and the area of gales around the storm extends out 300km.

The latest forecast track Map from RSMC Fiji, issued at 8:24am Friday Morning
The latest forecast track Map from RSMC Fiji, issued at 8:24am Friday Morning

Large waves, as well as storm surge, are likely to have a significant effect as the cyclone passes by New Zealand. Very large, long period, waves are likely from Cape Reinga to East Cape on Sunday and Monday, extending south to include Gisborne to the Kaikoura Coast Monday and Tuesday.

Wave spectra for Whakatane and Gisborne respectively below. Note the very long period waves (14-18 seconds) and the size (4+m). The longer the wave period, the more energy is contained within these waves and the better they reflect around obstacles such as islands and headlands.

Wave spectra chart for Whakatane
Wave spectra chart for Whakatane
Wave spectra chart for Gisborne
Wave spectra chart for Gisborne

[end]

Update Friday 13th March at 8:30am

JOHN LAW, METSERVICE METEOROLOGIST

Satellite image for 7am NZDT 13th March 2015
Satellite image for 7am NZDT 13th March 2015

Severe Tropical Cyclone Pam, currently a Category 5 cyclone moves southwards across Vanuatu while TC Nathan, Category 2, lingers off the coast of Queensland and is forecast to return to the east across the Coral Sea.

Just visible on this image is another tropical feature, this one is on the other side of the equator in the northern hemisphere. Tropical cyclone Bavi is forecast to move northwest over the next few days. Notice how the cloud wrapping into TC Pam is clockwise while in the north it is anticlockwise.

The Meteorological service of Vanuatu have issued warnings for many parts of the county for gales, heavy rain and large swells.

Tropical Cyclone Pam Updates – Thursday 12 March 2015

Update Thursday 12th March at 5:30pm

JOHN LAW, METSERVICE METEOROLOGIST

The forecasting team continue to monitor the progression of Tropical Cyclone Pam. By comparing the forecast tracks of several models the team have compiled a best track forecast for the position of the centre of the system as it tracks southwards.

Using the most recent data the system is forecast to pass just to the east of East Cape during the Monday. However, there is still a large degree of uncertainty in the exact path of the cyclone and although the centre may not pass over New Zealand, Severe Weather is likely to affect parts of the country – especially the northeast of the North Island. Stay up to date with the latest warnings here: http://metservice.com/warnings/home

In the diagram below the best forecast positions are indicated by the red line while the surrounding grey envelope gives an idea of the spread in the tracks the cyclone could take. Adverse weather associated with the cyclone may spread much wider than this envelope of tracks. With still several days to go, the forecast is likely to change and the team will continue to bring you the latest information.

Forecast path of cyclone Pam
Forecast track of Cyclone Pam shon in red, The surrounding grey envelopegives an idea of the spread in the tracks the cyclone could take.

The latest Severe Weather Outlook has been issued providing more information of severe weather forecast later in the weekend and into the early part of next week. Find out more at http://metservice.com/warnings/severe-weather-outlook

Find out more about what we mean by Severe Weather in this blog post: http://blog.metservice.com/2013/10/warnings-watches-and-outlooks/#

[end]

Update Thursday 12th March at 11.00am

JOHN LAW, METSERVICE METEOROLOGIST

Tropical Cyclone Pam remains in the tropics and continues to intensify. Currently a category 4, which by definition has mean winds between 86 and 107 knots (157-198 km/h), the track of the system remains southward just to the east of the southern Solomon Islands and Vanuatu.

TC Pam position as at 10am 12 March 2015
TC Pam position as at 10am 12 March 2015

The latest forecast from the Fiji Meteorological Service is for the cyclone to become a category 5 (mean wind speeds in excess of 107 knots or 198 km/h) at around 7am on Friday 13th (New Zealand time); at this stage the forecast position is to the east of northern Vanuatu.

TC Pam track from Fiji Met Service

Staying in the tropics, Tropical Cyclone Nathan remains off the coast of Queensland and is joined by another Tropical Cyclone, Olwyn, which is off the coast of Western Australia and will not affect New Zealand. For more information about these cyclones, head to Australia’s Bureau of Meteorology website.

What are the impacts on New Zealand?

We are still several days away from the cyclone reaching New Zealand waters and there is still plenty of uncertainty in the models. Knowing where the system moves is important in calculating the severity of the impacts on New Zealand.

MetService’s forecasting team look at information from a selection of different global models which use equations to model the physical properties of the atmosphere. Here are the latest model outputs for 1pm on Monday 16th March:

Model outputs for 1pm on Monday 16th March

 

As you can see, the general consensus of the models is for the lowest pressure to stay off to the north and the east of the country – but that does not mean we will avoid getting some stronger winds, heavy rainfall and high seas with this feature.

For the very latest thoughts from MetService’s meteorologists, head over to the Severe Weather Outlook which is updated by 15:00 NZST every day.

[end]

 

Tropical Cyclone Pam Updates – Wednesday 11 March

Update Wednesday 11th March, afternoon

JOHN LAW, METSERVICE METEOROLOGIST

From the Severe Weather Outlook issued at 2.34pm today, here’s the latest view on Pam’s potential effects on New Zealand:

Severe Weather Outlook
For the latest information head to http://metservice.com/warnings/severe-weather-outlook

A weak front should cross southern New Zealand on Friday, followed by a ridge of high pressure. The ridge should remain over the South Island until Monday. A southeast flow should develop over the North Island on Saturday and strengthen on Sunday as TC Pam moves out of the tropics and southeastwards.

TC Pam is expected to remain east of New Zealand, but parts of the North Island are likely to be affected by severe weather on Monday, especially Gisborne and northern Hawkes Bay, where there is a high confidence of warning amounts of heavy rain and severe southeast gales, possibly starting late Sunday.

For Northland, northern Auckland and the Coromandel Peninsula there is a low confidence that rain could become heavy late Sunday and southeast gales could become severe. However, the confidence increases to moderate on Monday, for both warning amounts of heavy rain in these areas and also severe gales. Southeasterlies are expected to turn southwest as the low tracks further south on Monday and there is also a risk of severe southwest gales.

Further south, there is a low confidence of rainfall accumulations reaching warning criteria in central and southern Hawkes Bay and also Wairarapa on Monday.

In addition, strong southeasterlies are likely to affect the remainder of the North Island and there is a moderate confidence that these could become severe about Auckland City, Waikato and Bay of Plenty. Winds may turn southwest later Monday about Auckland, and these southwest gales could also be severe. There is a low confidence of severe southeast gales for the rest of the North Island and the Marlborough Sounds on Monday.

Also of significance, unusually heavy northerly swell is expected to affect exposed coastlines from Cape Reinga to East Cape from later Sunday and during Monday. This swell has the potential to cause coastal damage and dangerous sea conditions.

The Chatham Islands are also likely to be affected by gales, heavy rain and unusually large swell from later Monday.

There is still considerable uncertainty regarding the track of TC Pam and severe weather watches and warnings will be issued as the situation evolves.

[end]

Update Wednesday 11th March, morning

JOHN LAW, METSERVICE METEOROLOGIST

Tropical Cyclone Pam continues to move southwards across the Pacific around 170E. The current track of the cyclone, which strengthened to a category 3 overnight, is between Vanuatu and Fiji.

TC Pam 11 March 8am

The meteorological service division of the Solomon Islands government has now issued a tropical cyclone warning for Temotu, Malaita and Makira provinces. For the latest information check their website http://www.met.gov.sb/

The latest forecast track for TC Pam from RSMC Nadi (based on data at 7am NZDT this morning) shows a maintained southerly movement and an expected intensification to category 4 during tomorrow (Thursday).

2015-03-10-18UTC-threat-track-map

 

For more information about the different categories head to this previous blog post.

The longer range forecast for the system continues to keep the centre to the north of the North Island before moving southwards to the east of New Zealand at the start of next week.

Pic3
An updated selection of different global models showing mean sea level pressure for 12UTC on Sunday 15th March (1am Monday NZDT) from the 1am model run from this morning (11/03/2015). Pressures lower than 1000hPa have been coloured blue.

 

 

Although the windiest and wettest weather looks likely to be offshore, there is still the possibility of southeasterly gales and rain affecting the northeast of the North Island. Strong winds and heavy rain may also be an issue for Raoul Island on Sunday and the Chatham Islands during the start of next week. For impacts over New Zealand, keep up to date with the latest Severe Weather Outlook over the next few days: http://www.metservice.com/warnings/severe-weather-outlook

As well as windy and wet weather, the system is also likely to bring high swells to the northern and eastern facing coasts during the weekend and into Monday. As always, please make sure you stay up to date with the latest forecasts before heading out onto the water.

In addition to Tropical Cyclone Pam, meteorologists across the South Pacific are also keeping an eye on Tropical Cyclone Nathan which has formed over the warm waters of the Coral Sea overnight last night. Although this system is currently forecast to remain offshore, the Australian Bureau of Meteorology has issued watches and warnings for parts of the Queensland coast.

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Tropical Cyclone Pam Updates – Tuesday 10 March 2015

Update for Tuesday afternoon, 10 March 2015

JOHN LAW, METSERVICE METEOROLOGIST

The latest guidance and advice from the Fiji Meteorological Service has upgraded Tropical Cyclone Pam to a category 2. This means that sustained wind speeds close to the centre of the system are in excess of 90km/h. The system is forecast to continue strengthening as it moves slowly to the southeast. At 1pm, New Zealand time, TC Pam was located at 9.7°S 170.4°E, with a central pressure of 985hPa. The latest track and position information can be found on the Fiji Met Service website.

Locating the centre of the tropical system is an important task and can be complicated by the presence of large amounts of high cloud and the lack of surface observations over the Pacific. One tool at the disposal of tropical specialists is microwave imagery of the tropical cyclone – which provides a unique view inside the cloud bands surrounding the cyclone.

Microwave imagery of TC PAM
This microwave image, from the American Naval Research Lab, has been coloured to highlight the deepest and most active cloud bands around the cyclone, shown in red and orange. Microwave imagery such as this can “see through” high cirrus cloud that might otherwise obscure the cyclone in traditional satellite imagery.

Where is Pam heading?

As the tropical system heads southwards it will be closely monitored by the meteorologists at MetService. This is just one of many possible tracks based on global model data. Note that while there is a general consensus on a track like this, the actual track and speed of the cyclone may be different and it will be important to keep up to date with the forecast.

Forecast Track TC Pam
This images shows one of several possible forecast traks for the tropical system.

One of the models that the forecasting team will be looking at is the one from the UK Met Office. You can find the latest output from this model here on metservice.com: http://www.metservice.com/maps-radar/rain-forecast/rain-forecast-5-day. Again, this is just one of many possible solutions, but as we’ve shown in the multi-model images, most of the models are in broad agreement. As the system moves southwards out of the tropics it will move over cooler waters causing the system to weaken.

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Update for Tuesday morning, 10 March 2015

JOHN LAW, METSERVICE METEROLOGIST

The track map for TC Pam issued earlier today by RSMC Nadi shows the cyclone intensifying to a Category 3 (on the Australian intensity scale) during Wednesday. As the cyclone moves south, it should begin to accelerate to the east of Vanuatu over the next few days, reaching almost as far south as Fiji by Friday morning.

2015-03-09-18utc-track-map
Forecast track map for TC Pam issued by RSMC-Nadi based on the analysis position at 7am, 10th March 2015. The grey shaded area shows the range of possible tracks the cyclone could take in the future.

The latest satellite image shows TC Pam over open waters north-northeast of Vanuatu, surrounded by a broad area of convection.

Infrared satellite image from midday (NZDT) Tuesday 10th March, 2015. Image courtesy JMA.
Infrared satellite image from midday (NZDT) Tuesday 10th March, 2015. Image courtesy JMA.

 

Whilst this is still a long way from New Zealand, MetService will continue to monitor TC Pam closely, as we issue a series of South Pacific Guidance charts every day as part of our responsibilities to the WMO’s Severe Weather Forecasting and Disaster Risk Reduction Demonstration Project (SWFDDP).

As an example, below is the chart valid for midnight on Wednesday. The dotted line indicates a change in threat level for swell heights: to the south a minimum of 3.5m swells are considered significant, whereas to the north where there are many low lying island nations, swells of 2.5m or more are considered significant. The core of strongest winds associated with TC Pam should not affect any of the land areas in the region over the next couple of days, but the swells those winds generate will fan out and could pose a significant threat to places like Tuvalu.

Part of the Southwest Pacific Guidance set produced each day by Lead forecasters at MetService. This chart is valid at 1am on Thursday 12th March.
Part of the Southwest Pacific Guidance set produced each day by Lead forecasters at MetService. This chart is valid at 1am on Thursday 12th March.

Looking further ahead to when TC Pam will reach the New Zealand area, the image below shows the low centre tracking east of New Zealand late on Sunday, according to a variety of global computer models from different agencies. This image is for 1am Monday 16th March, 24 hours after the image posted in the Monday 10 March blog.

TC Pam multi-model 12UTC 15th March
A selection of global models showing mean sea level pressure for 12UTC on Sunday 15th March (1am Monday NZDT). Pressures lower than 1000hPa have been coloured blue.

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