Monday 16th March 2015 7:35pm

BILL SINGH, METSERVICE METEOROLOGIST

At 6pm this evening Cyclone Pam was located about 350 km east of Gisborne. The system is intensifying as a mid latitude cyclone, and is moving southeast at 37 km/hr away from North Island. Rain accumulations from several stations in Gisborne and Hawkes  Bay are in excess of 150 mm in the last 24 hours. Pouturu Bridge and Te Puia stations have reported over  200mm of rain for the same period. The latest radar image below shows that rain has eased in northern parts of Gisborne, and this easing trend is expected to continue for Gisborne, northern Hawkes Bay this evening and remaining eastern areas early morning.  Hicks Bay, Gisborne has recorded southerly winds gusts of 78 knots (140 km/h) around 1 pm today. Severe southerly gales in Gisborne, Hawkes Bay, Wellington and heavy swells and very large waves about the eastern coastal areas are all expected to ease tomorrow.

Please keep updated with the latest watches and warnings here .

Radar image(left) and IR satellite image (right) at 6:30 pm today Radar image(left) and IR satellite image (right) at 6:30 pm today

On its current track, cyclone Pam, denoted as an "L" on the track chart shown below,  is expected to be located about 260 km northeast of Chatham Islands at midday Tuesday, while continuing in the southeast track. A warning is also in force for the Chatham Islands for severe gales, heavy rain and heavy swells.

The historical track of Cyclone Pam (red line) and its forecast track (blue line) with forecast positions marked as circled L’s in universal coordinated time (NZST = UTC +13 hours). The historical track of Cyclone Pam (red line) and its forecast track (blue line) with forecast positions marked as circled L’s in universal coordinated time (NZST = UTC +13 hours).

 

Monday 16 March 2015 1:30 pm

WILLIAM NEPE, METSERVICE METEOROLOGIST

RGB Cyclone Pam 16 March 2015 1051NZDT A composite RGB satellite image courtesy of NOAA taken at 10:51am NZST this morning. Cloud can be seen northeast of Gisborne wrapping around and into Cyclone Pam.

At 1pm this afternoon Cyclone Pam was located about 230 km east of East Cape, Gisborne. Pam's central pressure has remained about the same in the last 6 hours (962 hPa), but is expected to slowly intensify during today and tomorrow as it moves towards the Chatham Islands. A warning is in force for the Chatham Islands for severe gales, heavy rain and heavy swells expected tomorrow.

The historical track of Cyclone Pam (red line) and its forecast track (blue line) with forecast positions marked as circled L's in universal coordinated time (NZST = UTC +13 hours). The historical track of Cyclone Pam (red line) and its forecast track (blue line) with forecast positions marked as circled L's in universal coordinated time (NZST = UTC +13 hours).

The image below shows satellite derived winds over the ocean at around 10:48am this morning, with clockwise winds in excess of 45 knots (80 km/h) in the western and southern quadrants of Cyclone Pam, northeast of Gisborne. Hicks Bay, Gisborne has recorded southerly winds with hourly mean speeds of 50 knots (90 km/h) over the last 2 hours and gusts of 70 knots (130 km/h).

Satellite derived winds over the ocean at 10:48am NZST this morning showing clockwise winds about Cyclone Pam northeast of Gisborne .

Heavy rain continues to fall in the ranges of Gisborne, with accumulations at several stations now in excess of 150 mm in the last 24 hours.

A radar image from 12:51pm this afternoon showing rain falling into eastern and southern parts of the lower North Island.

Severe winds, heavy rain and phenomenal waves are expected to continue over eastern and southern parts of the North Island during today and tomorrow including the Chatham Islands. Keep updated with the latest warnings here http://www.metservice.com/warnings/home as well as the MetService Blog here http://blog.metservice.com/.

Monday 16 March 2015 10:30 am

WILLIAM NEPE, METSERVICE METEOROLOGIST

At 10am this morning Cyclone Pam was located about 230 km east-northeast of East Cape, Gisborne. Despite being re-classified as an extra-tropical cyclone in the early hours of this morning, the system still has severe weather which is affecting parts of New Zealand.

Cyclone Pam ("L") located about 230km northeast of East Cape at 10am this morning. The picture shows Cyclone Pam ("L") analysed about 230km east-northeast of East Cape at 10am this morning. The white lines show the mean sea level pressure in hecto-pascals. The JMA MTSAT infrared satellite image is overlaid and shows the displacement of the high cloud from the system centre, indicative of extra-tropical transition.

The image below shows Cyclone Pam's forecast track (blue line) over the next 36 hours and the systems historical track (red line) over the last 7 days. The system is moving south and should lie about 180 km east of East Cape around 1pm today (16/0000 UTC) and just northeast of the Chatham Islands around 1pm Tuesday (17/0000 UTC). It is expected to maintain its intensity or intensify slightly as it moves southeast.

The historical track of Cyclone Pam (red line) and its forecast track (blue line) with forecast positions marked as circled L's in universal coordinated time (NZST = UTC +13 hours). The forecast track (blue line) with forecast positions marked as circled L's in universal coordinated time (NZST = UTC +13 hours), and its historical track (red line) over the last 7 days.

The effect of Cyclone Pam is being felt over parts of New Zealand in particular Gisborne, with rain accumulations recorded in excess of 100 mm  in the last 12 hours, and wind gusts of 130 km/h in Hicks Bay. The system is also causing large waves along the east coast from Northland down to Gisborne, with reports of easterly waves in excess of 4 metres.

A radar image from 9:51am this morning clearly showing the rain falling into eastern and northern parts of the North Island, while western parts are sheltered. A radar image from 9:51am this morning showing the rain falling into eastern and northern parts of the North Island, while western parts are sheltered.

As the system continues moving south-southeast into tomorrow, it is expected to impact the Chatham Islands. A warning has been issued as follows:

Forecast for Land areas of the Chatham Islands:
East to southeast winds are expected to rise to gale Monday evening,
and south to southeast severe gale Monday night. The winds are then
expected to remain severe gale as they turn southwest during Tuesday,
then gradually ease Wednesday morning. Peak winds are expected to be
during Tuesday morning and early afternoon.

Gusts of 130 to 160km/h are expected with the severe gales.
Winds of this strength have the potential to topple trees, damage
powerlines, lift roofs and make driving conditions hazardous.
In addition, a period heavy rain is likely from Monday evening
through to Tuesday evening, when 70 to 90mm could accumulate,
although there is greater uncertainty as to the amount of rainfall.

Heavy swells of 6 metres and large combined seas of 9 metres or more
are expected to affect the Chatham Islands from Monday evening
through to Wednesday. Initially, swell is expected to be from the
north with a long period and should arrive tonight (Monday), then
during Tuesday expect a shorter period heavy easterly swell. Finally,
a heavy south to southwest swell is expected during Wednesday and
Thursday. These swells have the potential to cause damage, especially to
northern and eastern coastal areas. Please refer to Marine forecasts
for Coastal and High Seas information.
Next update: Midday Monday 16th March 

Severe winds, heavy rain and phenomenal waves are expected to continue over parts of the country during today and tomorrow. Keep updated with the latest warnings here http://www.metservice.com/warnings/home as well as the MetService Blog here http://blog.metservice.com

 

Monday 16 March 2015 7:30 am

WILLIAM NEPE, METSERVICE METEOROLOGIST

Cyclone Pam has now been re-classified as an intense extra tropical cyclone. It is expected to maintain its intensity or intensify slightly as it moves southeast. The satellite image below from 7am this morning shows Cyclone Pam (marked "L") was located about 300 km northeast of East Cape.  The system is moving southeast 30 km/h and is expected to lie about 150 km east of East Cape at midday today, and just northeast of the Chatham Islands at midday Tuesday.

Cyclone Pam located about 300km northeast of East Cape at 7am this morning. Cyclone Pam located about 300km northeast of East Cape at 7am this morning.

The effect of Cyclone Pam is being felt over New Zealand with wind gusts of 130-140 km/h observed in Northland last evening, and heavy rain has fallen in Gisborne with 100-150mm accumulated in some areas since 5pm yesterday.

Rain radar image from 6:51am Monday Rain radar image from 6:51am Monday

 

 

 

 

 

 

Extremely strong wind gusts, heavy rain and phenomenal waves are expected over parts of the country, and details can be found at http://www.metservice.com/warnings/home as well as at http://blog.metservice.com/ or http://www.metservice.com/national/home

 

Monday 16 March 2015 4:00am

HORDUR THORDARSON, METSERVICE METEOROLOGIST

Cyclone Pam has now been re classified as an intense extra tropical cyclone. It is expected to maintain its intensity or intensify slightly as it moves south-southeast. At midnight it was located some 450 kilometres north of East Cape. It is expected to lie some 150 kilometres east of East Cape at midday today. It is then likely to continue moving east-southeast and lie just northeast of the Chatham Islands at midday Tuesday.

This image from 1:30am Monday morning shows that westerly winds at upper levels have pulled the high cloud away from the cyclone’s centre marked by C. This is indicative of the transition from a tropical to an extra tropical cyclone.

 

Infra red image from 1:30am local time Infra red image from 1:30am local time

 

The effects of Cyclone Pam are already being felt in some areas. A wind gust to 150 kilometres per hour was observed near Kaeo in Northland and a gust of 144 kilometres an hour was observed at Channel Island between Coromandel Peninsula and Great Barrier Island Sunday evening. Rain has become heavy in Gisborne and and more than 100mm have already accumulated in some areas.

 

Rain radar image from 3:30am Monday Rain radar image from 3:30am Monday

 

Reclassification does not mean that “Pam” no longer poses any threat. Extremely strong wind gusts, heavy rain and phenomenal waves are still expected, and details can be found in http://www.metservice.com/warnings/home as well as in http://blog.metservice.com/ or http://www.metservice.com/national/home

Sunday 16 March 2015 1:00am

HORDUR THORDARSON, METSERVICE METEOROLOGIST

Category 3 Cyclone Pam was lying near 34S 178.5E at midnight, or about 450 kilometres northeast of Auckland and 450 kilometres north of East Cape on a track to the south-southeast as shown on the image below.

Track

The effects of Cyclone Pam are already being felt in some areas. A wind gust to 150 kilometres per hour was observed near Kaeo in Northland and a gust of 144 kilometres an hour was observed at Channel Island between Coromandel Peninsula and Great Barrier Island this evening. Rain is becoming heavy in Gisborne and and 70mm have already accumulated in some areas there.

Rain radar at 11pm Sunday Rain radar at 11pm Sunday

 

Pam is expected to be reclassified early this morning and will from then on be considered an extra tropical cyclone.

Infra red image at 11pm Sunday Infra red image at 11pm Sunday

Why will it be re classified? The reason for this is that the nature of the system changes. A tropical cyclone derives its energy from latent heat released in strong deep convection. Warm moist air over a warm sea surface rises, condenses, warms further and continues to rise. This is the energy that intensifies and maintains a tropical cyclone. Once the cyclone moves south out of the tropics and over cooler waters this energy source decreases. Normally this will lead to a slow weakening of the system.

There is however a new energy source that becomes available to the storm as it moves out of the tropics. This energy comes from the difference between hot and cold air. If there is a large temperature difference over a relatively short distance this can be a powerful source of energy that re-energises the storm as it moves out of the tropics.

The main differences between a tropical cyclone and an extra tropical cyclone are:

Tropical Cyclone                                                Extra tropical cyclone

No fronts                                                             Fronts

Winds max close the centre                           Wind maximum well away front the centre

Driven by latent heat release                         Strong temperature gradients

 

Reclassification does not mean that “Pam” no longer poses any threat. Extremely strong wind gusts, heavy rain and phenomenal waves are still expected, and details can be found in http://www.metservice.com/warnings/home as well as in http://blog.metservice.com/ or http://www.metservice.com/national/home