Tuesday 17th March 2015 4pm

HANNAH MOES, METSERVICE METEOROLOGIST

At midday on Tuesday the centre of Cyclone Pam was located about 280km northeast of the Chatham Islands, with a central pressure of 945hPa.

Enhanced infra-red satellite image from Tuesday at 3pm New Zealand time showing Cyclone Pam to the east of the country. Enhanced infra-red satellite image from Tuesday at 3pm New Zealand time showing Cyclone Pam to the east of the country.
Modis high resolution polar-orbiting satellite image of Cyclone Pam near the Chatham Islands at 2.45pm 17/03/2015 Modis high resolution polar-orbiting satellite image of Cyclone Pam near the Chatham Islands at 2.45pm 17/03/2015

Cyclone Pam remains an intense extra-tropical low, but will gradually move southeast away from the Chatham Islands over the next 48 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 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 pressure at the Chatham Islands has been steadily falling as the centre of Cyclone Pam moved closer to the Islands over the last 24 hours. The below chart shows the relationship between falling pressure and increasing wind strength.

In this image the wind speed is shown in the top graph, steadily increasing, while in the bottom graph the pressure is falling rapidly as the system moves closer and closer to the weather station at the Chatham Islands site. In this image the wind speed is shown in the top graph, steadily increasing, while in the bottom graph the pressure is falling rapidly as the system moves closer to the weather station at the Chatham Islands site.

Rain began falling at the Chatham Islands around 5pm yesterday (Monday), and rainfall accumulations recorded there have since reached 61mm in the 22 hours to 3pm today. A severe weather warning remains in place for further rainfall there until late Wednesday.

Southeast winds peaked at severe gale 83 km/h gusting 109 km/h at 9am this morning. Winds turned southwest this afternoon, and are expected to remain at severe gale strength until Wednesday evening.

Large northerly swells are now easing at the Chatham Islands. Easterly swells are forecast to rise to 4 metres this evening, before easing tomorrow (Wednesday) morning. Finally, a southerly swell of 4 metres will begin to affect the Islands during tomorrow.

Please note, all times specified above are in New Zealand Local Time (NZLT) unless otherwise stated. Universal Co-ordinated Time (UTC) is NZLT-13 hours. Chatham Islands Local Time is NZLT+45 minutes.

Tuesday 17th March 2015 11:30 am

JOHN LAW, METSERVICE METEOROLOGIST

An enhanced infra-red satellite image from Tuesday at 9am New Zealand time showing Cyclone Pam to the east of the country. An enhanced infra-red satellite image from Tuesday at 9am New Zealand time showing Cyclone Pam to the east of the country.

Cyclone Pam remains an intense extra-tropical low. At 9:00am on Tuesday morning the centre of the system was about 400km northnortheast of the Chatham Islands moving on a southeast trajectory.

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 Severe Weather forecasting team have been incredibly busy over the last few weeks updating the forecasts, watches and warnings. All Severe Weather Warnings and Watches were lifted this morning at 9.30 am, except for the Chatham Islands which continue to have warnings for gales, heavy rain and high swell amounts.

Although Cyclone Pam is pulling further away from the North and South Islands the conditions around the coast from East Cape to Banks Peninsula continue to be rough. Heavy swell and large waves are expected today (Tuesday), before easing on Wednesday. Please check the latest marine forecasts before heading out.

Chatham Islands Warning
Cyclone Pam, currently 400km northnortheast of the Chatham Islands, is expected to remain a very deep low while moving southeast to lie about 450km eastsoutheast of the Chatham Islands by midnight tonight (Tuesday). Damaging gales, rain and heavy swells are expected to last through into Wednesday evening.

Forecast for Land areas of the Chatham Islands:
Severe gale southeasterlies are expected to turn southwest this afternoon and remain severe gale, then gradually ease Wednesday evening. Peak winds are expected from later this morning (Tuesday) until tonight, with damaging gusts of 120 to 140km/h. Winds of this strength have the potential to topple trees, damage powerlines and structures, and make driving conditions hazardous.

In addition, heavy rain is likely to continue today (Tuesday), where another 40 to 60mm could accumulate on top of what has already fallen. This amount of rain could cause surface flooding and slips. Heavy swells of 6 metres and large combined seas of 9 metres or more are expected to affect the Chatham Islands through to Thursday. Initially, swell is expected to be from the northeast with a long period, then later on 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.

Next update: 9pm Tuesday 17 March 2015

Please refer to Marine forecasts for Coastal and High Seas information.

The last 24 hours of observations from the Chatham Islands show the link between the dropping pressure and the strengthening winds.

In this image the wind speed is shown in the top graph, steadily increasing, while in the bottom graph the pressure is falling rapidly as the system moves closer and closer to the weather station at the Chatham Islands website. In this image the wind speed is shown in the top graph, steadily increasing, while in the bottom graph the pressure is falling rapidly as the system moves closer and closer to the weather station at the Chatham Islands airport.

Tuesday 17th March 2015 5:00 am

HORDUR THORDARSON, METSERVICE METEOROLOGIST

At midnight Monday Cyclone Pam was located about 400 km east of the North Island and some 500 km north of the Chatham Islands. The system is intensifying as a mid latitude cyclone, and is moving southeast away from North Island. The central pressure is expected to be close to 940 hectoPascals late today, Tuesday.

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).

Rain accumulations from several stations in Gisborne and Hawkes Bay were in excess of 150mm during Monday but the rain has now eased.  Hicks Bay in Gisborne recorded southerly winds gusts of 78 knots (140 km/h) around 1 pm on Monday. Southerly gales in Gisborne and Hawkes Bay and heavy swells about the eastern coastal areas are all expected to ease today. However, the southerlies may rise to severe gale in Wellington this morning and a watch has been issued.

Infra red satellite image from 4am local time. Infra red satellite image from 4am local time.

On its current track, cyclone Pam is expected to be located about 260 km northeast of Chatham Islands at midday today, while continuing on a southeast track. A warning is in force for the Chatham Islands for severe gales, heavy rain and heavy swells. Peak winds there are expected this morning and early afternoon, with damaging gusts of 130 to 160km/h. A period of heavy rain is expected through to this evening and 80 to 110mm could accumulate.

 

Tuesday 17th March 2015 1:00 am

HORDUR THORDARSON, METSERVICE METEOROLOGIST

At midnight Monday Cyclone Pam was located about 400 km east of the North Island and some 500 km north of the Chatham Islands. The system is intensifying as a mid latitude cyclone, and is moving southeast away from North Island. The central pressure is expected to be close to 940 hectoPascals late today, Tuesday.

Rain accumulations from several stations in Gisborne and Hawkes  Bay are in excess of 150 mm in the last 24 hours. The latest radar image below shows that rain has eased in Gisborne and Hawkes Bay.  Hicks Bay, Gisborne has recorded southerly winds gusts of 78 knots (140 km/h) around 1 pm on Monday. Severe southerly gales in Gisborne and Hawkes Bay and heavy swells about the eastern coastal areas are all expected to ease today. However, the southerlies may rise to severe gale in Wellington this morning and a watch has been issued.

Rain radar at midnight showing that the main rainband has pulled away from the North Island Rain radar at midnight showing that the main rainband has pulled away from the North Island

 

 

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).

 

On its current track, cyclone Pam, denoted as an “L” on the track chart shown above,  is expected to be located about 260 km northeast of Chatham Islands at midday Tuesday, while continuing on a southeast track. A warning is in force for the Chatham Islands for severe gales, heavy rain and heavy swells. Peak winds there are expected this morning and early afternoon, with damaging gusts of 130 to 160km/h. A period of heavy rain is expected through to this evening.

 

Infra red satellite image from midnight. Infra red satellite image from midnight.