National Climate Summary Jan 2010: Wet and Cloudy

NATIONAL CLIMATE CENTRE Tuesday 2 February 2010

National Climate Summary – January 2010: Wet and cloudy for much of the country.

• Rainfall: Exceptionally wet in the east of the North Island and parts of the Waikato following heavy rainfall on the 31st. Above normal rainfall for most other regions of New Zealand – the notable exceptions being Northland and parts of coastal Canterbury and north Otago, which recorded well below normal rainfall.
• Soil moisture: Severe soil moisture deficits continue in Northland.
• Temperature: Near average temperatures across much of the country. Small pockets of below average temperatures in Manuwatu-Wanganui, Wairarapa and southern Hawkes Bay, south Canterbury and in the Clutha.
• Sunshine: Extremely cloudy over the lower North Island, and eastern South Island. Very sunny in Northland.

Overall, January 2010 was an unsettled month, being wet, slightly cool, and extremely cloudy. The month was characterised by lower pressures than normal over the country.

The most significant extreme weather event to impact on the country in January was the heavy rainfall event on January 31st, which affected the eastern and central North Island, as well as Waikato and Coromandel. A moist, easterly air stream brought heavy rain and embedded thunderstorms to these areas, causing flooding, slips, and road closures. Particularly hard hit were Gisborne and Hawkes Bay. This one event produced most of the month’s rainfall total in these regions. More than double normal January rainfall was recorded in Gisborne, Hawkes Bay, the Wairarapa and in parts of the Waikato. Above normal rainfall (between 120 and 150 percent of normal) was also recorded in most other regions of New Zealand. The notable exception was Northland, which experienced well below normal rainfall (less than 50 percent of January normal) with severe soil moisture deficits continuing through to the end of January. Other areas which experienced below normal rainfall (between 50 and 70 percent of January normal) were coastal Canterbury and north Otago.

Overall, January temperatures were near average (between -0.5°C and 0.5°C of average) across most of New Zealand. The exceptions were small pockets of below average temperatures (between 1.2°C and 0.5°C below average) in Manawatu-Wanganui, the Wairarapa and southern Hawkes Bay, south Canterbury and in the Clutha district. The New Zealand national average temperature for January was 16.7°C (0.4°C below the long-term January average).

January sunshine totals were well below normal (below 75 percent of normal) over the lower North Island, and the entire eastern South Island, from Blenheim to Dunedin. In contrast, Northland experienced a very sunny month, with sunshine totals between 110 and 125 percent of normal. Elsewhere, sunshine totals were close to normal.

Further Highlights:
• The highest temperature was 34.3°C recorded at Blenheim on the 1st (not a January record). The lowest temperature of -0.3 °C was recorded at Alfredton on the 24th (not a record for January).
• The highest 1-day rainfall was 202.6 mm, recorded at Franz Josef on the 6th (not a January record).
• The highest wind gust was 165 km/hr, recorded at Stewart Island on the 1st (not a record for January).
• Of the six main centres, Tauranga was the warmest and sunniest, Hamilton the wettest, Dunedin the coolest, and Christchurch the driest.

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RAINFALL: EXCEPTIONALLY WET IN EAST OF NORTH ISLAND AND IN PARTS OF WAIKATO. ABOVE NORMAL RAINFALL IN MOST OTHER REGIONS OF THE COUNTRY. CONTINUING DRY IN NORTHLAND, COASTAL CANTERBURY AND NORTH OTAGO.

The most significant extreme weather event to impact on the country in January was the heavy rainfall event on January 31st, which affected the eastern and central North Island, as well as Waikato and Coromandel. A moist, easterly air stream brought heavy rain and embedded thunderstorms to these areas, causing flooding, slips, and road closures. Particularly hard hit were Gisborne and Hawkes Bay. This one event produced most of the month’s rainfall total in these regions. More than double normal January rainfall was recorded in Gisborne, Hawkes Bay, the Wairarapa and in parts of the Waikato.

Above normal rainfall (between 120 and 150 percent of normal) was also recorded over most other regions of New Zealand. The notable exception was Northland, which experienced well below normal rainfall (less than 50 percent of January normal) and which continues to be in a drought state, with severe soil moisture deficits persisting through to the end of January. Other areas which experienced below normal rainfall (between 50 and 70 percent of January normal) were coastal Canterbury and north Otago.

Record or near-record January rainfall totals were recorded at:

Location Rainfall total (mm) Percentage of normal Year records began Comments
Matamata 138 179 1951 2nd-highest
Hamilton 192 239 1935 2nd-highest
Takapau Plains 189 273 1962 3rd-highest
Castlepoint 321 601 1902 Highest
Gisborne 171 307 1905 3rd-highest
Napier 195 365 1870 4th-highest
Waipawa 188 497 1945 3rd-highest
Wairoa, North Clyde 281 292 1964 2nd-highest
Ohakune 198 191 1961 Highest
Lumsden 140 136 1982 2nd-highest

Oamaru 18 35 1898 4th-lowest

TEMPERATURES: NEAR AVERAGE FOR MUCH OF COUNTRY. SMALL POCKETS OF BELOW AVERAGE TEMPERATURES IN MANAWATU-WANGANUI, WAIRARAPA, SOUTHERN HAWKES BAY, SOUTH CANTERBURY AND THE CLUTHA.

Overall, January temperatures were near average (between -0.5°C and 0.5°C of average) across most of New Zealand. The exceptions were small pockets of below average temperatures (between 1.2°C and 0.5°C below average) in Manawatu-Wanganui, the Wairarapa and southern Hawkes Bay, south Canterbury and in the Clutha district. The New Zealand national average temperature was 16.7°C (0.4°C below the long-term January average).

Record or near-record January mean maximum daily air temperatures were recorded at:

Location Mean maximum air temperature (°C) Departure from normal (°C) Year records began Comments
Whangaparaoa 23.9 1.6 1982 2nd-highest

Kaitaia 22.4 -1.5 1967 Lowest
Kumeu 23.0 -0.6 1978 4th-lowest
Castlepoint 18.7 -2.8 1972 2nd-lowest
Wanganui 20.4 -1.7 1987 Lowest
Cape Campbell 18.5 -3.5 1953 Lowest
Cheviot 22.4 -0.7 1982 3rd-lowest
Orari Estate 19.9 -2.4 1972 4th-lowest
Balclutha, Telford 17.7 -2.4 1964 2nd-lowest
Nugget Point 16.0 -1.7 1970 3rd-lowest

Record or near-record January mean minimum daily air temperatures were recorded at:

Location Mean minimum air temperature (°C) Departure from normal (°C) Year records began Comments
Kaitaia 12.8 -2.3 1967 4th-lowest
Warkworth 13.6 -1.5 1966 3rd-lowest
Dunedin 8.6 -0.6 1947 2nd-lowest

SUNSHINE: EXTREMELY CLOUDY OVER LOWER NORTH ISLAND, AND EAST OF SOUTH ISLAND. VERY SUNNY IN NORTHLAND.

January sunshine totals were well below normal (below 75 percent of normal) over the lower North Island, and the entire eastern South Island, from Blenheim to Dunedin. In contrast, Northland experienced a very sunny month, with sunshine totals between 110 and 125 percent of normal. Elsewhere, sunshine totals were close to normal.

Record or near-record January sunshine hours were recorded at:

Location Sunshine (hours) Percentage Of normal Year records began Comments
Kaitaia 277 121 1985 4th-highest

Martinborough 173 75 1986 Lowest
Wallaceville 164 72 1939 3rd-lowest
Stratford 172 76 1963 3rd-lowest
Blenheim 221 85 1947 3rd-lowest
Cheviot 181 76 1983 2nd-lowest
Lake Tekapo 193 77 1928 4th-lowest
Cromwell 214 89 1979 3rd-lowest

JANUARY CLIMATE IN THE SIX MAIN CENTRES

It was an extremely wet January for Tauranga, Hamilton and Wellington, with at least double normal January rainfalls experienced. Near normal rainfall was recorded in Auckland and Dunedin, while Christchurch experienced below normal January rainfall. Monthly temperatures were below average in Auckland, Wellington and Dunedin, and near average in Tauranga, Hamilton, and Christchurch. Sunshine totals for January were near normal in all main centres except for Wellington and Christchurch, which both recorded about three-quarters of usual January sunshine. Of the six main centres, Tauranga was the warmest and sunniest, Hamilton the wettest, Dunedin the coolest, and Christchurch the driest.

January 2010 main centre climate statistics:

Location Mean temp. (°C) Departure from normal (°C) Rainfall (mm) % of normal Sunshine (hours) % of normal
Aucklanda 19.0 -0.7 Below average 51 84% Near normal 239 104% Near normal
Taurangab 19.5 +0.3 Near average 178 244% Well above normal 262 104% Near normal
Hamiltonc 18.3 +0.1 Near average 192 239% 2nd highest since 1935 233g 100% Near normal
Wellingtond 15.9 -1.0 Below average 165 229% Well above normal 181 74% Well below normal
Christchurche 16.6 -0.5 Near average 33 76% Below normal 174 76% Below normal
Dunedinf 14.3 -0.9 Below average 69 96% Near normal 171 96% Near normal
a Mangere b Tauranga Airport c Hamilton Airport d Kelburn e Christchurch Airport f Musselburgh g Ruakura

HIGHLIGHTS AND EXTREME EVENTS

• Temperature

The highest temperature in January 2010 was 34.3°C recorded at Blenheim on the 1st (not a January record at this site).

Record or near-record warm afternoon conditions were experienced at several sites at the end of the month (29th, 30th, 31st January), linked to sub-tropical, easterly conditions. Notably, several sites recorded near-record high temperatures on the 31st of the month on the West Coast of the South Island, showing foehn warming with these easterly winds.

Record or near-record low afternoon temperatures were recorded over the lower North Island on the 16th, over the south-eastern South Island on the 8th, and over the far south of the country on the 11th.

Record or near-record daily maximum air temperatures were recorded at:

Location Extreme maximum temperature (ºC) Date of extreme temperature Year Records began Comments
Kaitaia 28.4 29th 1985 Equal 3rd-highest
Whangaparaoa 28.6 30th 1982 Highest
Wallaceville 30.3 29th 1939 3rd-highest
Hawera 26.6 20th 1977 2nd-highest
Westport 28.5 31st 1937 Highest
Hokitika 27.7 31st 1963 3rd-highest
Milford Sound 27.9 31st 1934 2nd-highest
Puysegur Point 23.1 17th 1978 4th-highest
Le Bons Bay 28.7 2nd 1984 3rd-highest
Woodbury 33.0 1st 1973 4th-highest

Kaitaia 18.8 23rd 1971 3rd-lowest
Martinborough 14.4 16th 1986 3rd-lowest
Ngawi 13.3 16th 1972 4th-lowest
Napier 16.0 16th 1973 Lowest
Wellington 13.3 16th 1972 Equal 2nd-lowest
Westport 15.0 10th 1966 Equal 3rd-lowest
Greymouth 13.8 4th 1972 Lowest
Puysegur Point 10.6 11th 1978 Lowest
Arthurs Pass 9.6 10th 1973 Equal 4th-lowest
Dunedin 12.0 8th 1972 3rd-lowest
Queenstown 11.0 8th 1972 Equal 3rd-lowest
Tiwai Point 11.9 11th 1972 4th-lowest
Balclutha, Telford 11.8 8th 1972 Equal 4th-lowest

The lowest temperature recorded in January 2010 was -0.3 °C, recorded at Alfredton on the 24th (not a January record at this site).

Record or near-record daily minimum air temperatures were recorded at:

Location Extreme minimum temperature (ºC) Date of extreme temperature Year Records began Comments
Kaitaia 7.8 10th 1967 Equal 3rd-lowest
Warkworth 6.4 10th 1966 Equal lowest
Whangaparaoa 11.1 12th 1982 2nd-lowest
Taupo 2.0 9th 1976 4th-lowest

Whangaparaoa 19.8 31st 1982 3rd-highest
Whakatane 20.0 26th 1975 Equal 2nd-highest
Hamilton 19.0 21st 1972 Equal 4th-highest
Napier 22.0 4th 1973 2nd-highest
Waipawa 19.3 4th 1945 Equal 3rd-highest
Greymouth 18.4 17th 1972 Equal 2nd-highest

• Heavy rain, flooding, lightning and hail

The highest 1-day rainfall total for January was 202.6 mm recorded at Franz Josef on the 6th (not a January record at this location). Record high 1-day rainfalls for January were also recorded at several locations in the Waikato, Bay of Plenty, Gisborne and Hawkes Bay regions on the 31st, associated with moist easterly conditions and embedded thunderstorm activity over North Island. On January 21st, several central Otago and Southland sites experienced near-record high January 1-day rainfall totals, also linked to thunderstorm activity.

Record or near record high extreme 1-day rainfall totals were recorded at:

Location Extreme 1-day rainfall (mm) Date of extreme rainfall Year Records Began Comments
Matamata 85 31st 1951 Highest
Tauranga 120 31st 1910 2nd-highest
Whatawhata 61 31st 1952 3rd-highest
Hamilton 78 31st 1935 3rd-highest
Masterton 84 22nd 1926 Highest
Castlepoint 160 22nd 1907 Highest
Gisborne 58 30th 1937 4th-highest
Waipawa 66 22nd 1945 3rd-highest
Wairoa, North Clyde 83 31st 1967 2nd-highest
Lumsden 53 21st 1982 2nd-highest
Cromwell 48 21st 1949 2nd-highest
Alexandra 39 21st 1983 2nd-highest

On 3 January, SH6, south of Fox Glacier, was closed for more than six hours after the northern bank of Bullock Creek broke.

In the 10 minutes before 2 pm on 7 January, Invercargill Airport recorded 8.4 mm of rain. The intense rainfall was caused by an intense mid-afternoon thunderstorm, with hail covering northern and central Invercargill. Buildings throughout the CBD, including the Southland District Council and the Invercargill Public Library, were flooded by water pouring in from outside. The thunderstorm also caused electricity cuts, which affected 3500 customers in south Invercargill, Bluff and Awarua. A horse died instantly when it was struck by lightning in a paddock on the outskirts of Invercargill. On the West Coast, the rain caused slips, flooding and closed roads. The Totara River, north of Ross, cut a new course about 1 pm, spilling into a paddock, closing SH6 for over an hour. The road was also closed by flooding between Fox Glacier and Haast, but re-opened about 2.30 pm. Surface flooding closed the Kaniere-Kowhitirangi Road from mid-afternoon.

The Desert Road was closed by heavy rain about 10.30 pm on 15 January, and re-opened the following morning.

On 16 January, heavy rain flooded campsites in the Wairarapa, and closed Paekakariki Hill Road, north of Wellington, when a slip and large trees blocked both lanes. The Wairoa A&P Show, held over the weekend of 16-17 January, was also affected by heavy rain, with events such as woodchopping, equestrian, and
shearing either cancelled, cut back, or moved to an alternative location.

On 21 January, thunderstorm activity associated with a complex low over the country affected the Ida Valley, Central Otago, producing very intense rainfall rates. On the same day, thunderstorms and lightning affected the water treatment plant in Hamilton.

On 22 January, heavy rain flooded streets in Flaxmere, near Hastings, and closed SH50 between Ongaonga and Tikokino. The flash flooding was caused by downpours from thunderstorms in the area. Overnight on 22-23 January, Hawkes Bay experienced about 2000 lightning strikes. On 23 January, heavy rain caused a large slip on SH5, near Titiokura Summit, with one lane closed, and other sections of the road affected by flooding.

On 26 January lightning struck the central North Island, especially Taranaki, Taumarunui and South Waikato. On 27 January, torrential rain caused flooding in the Fairy Springs Road area of Rotorua, and blocked SH1 near Lake Karapiro. Several homes in Cambridge were flooded. Again, the downpours were caused by thunderstorm activity, with a severe electrical storm centred directly over Hamilton City.

Exceptionally heavy rain, associated with moist easterly conditions and numerous embedded thunderstorms, affected the North Island on 31 January, causing slips, and floods, and closing SH5 between Napier and Taupo, and SH2 north of Gisborne. Rising floodwaters and debris buckled a bridge on the Waipaoa River, isolating more than 30 people at Waipaoa Station. Mangatuna village residents were moved out in the morning as the Uawa River rose, allowed to return several hours later, but were evacuated again in the afternoon. In the Coromandel, Hahei and the Hot Water Beach area were cut off by flooding on Hot Water Beach Road, 200 m from SH25, SH25a, was closed by flooding near Hikuai and Duck Creek, Tairua was accessible from the north but not from the south, and SH25 at Onemana near Opoutere was blocked by flooding. In the Auckland region, homes were flooded on the Whangaparaoa Peninsula, North Shore, Auckland City, and Howick. A woman was trapped in her car by rising floodwaters underneath a motorway overpass in Ellerslie, and another driver was trapped by flood water in Remuera.

• High winds

Gales hit the bottom of the South Island on 1 January damaging trees in Invercargill. In South Canterbury, SH 8 between Lakes Pukaki and Tekapo was closed at about 6pm to motorcycles and high-sided vehicles. In Wanaka, a power line was brought down by the gale, disrupting power supplies. The highest wind gust for January was 165 km/hr, recorded at Southwest Cape (Stewart Island) on the 1st (not a January record at this site). Gore also recorded near-record high gusts on this date.

On 3 January, winds created havoc during the annual New Year Regatta in Napier, with one girl concussed, and another fished out of the water after boats collided. About half of the 120 boats, competing in 12 classes, withdrew from the regatta. Strong winds were also recorded in Wellington, with Mt. Kaukau recording an extreme gust of 145 km/hr.

On 31 January, gale force winds battered Taranaki, bringing down power lines and trees. The electricity supply was cut to parts of New Plymouth city, Bell Block, and Patea. SH45 near Lucy's Gully, and SH3, just south of Egmont Village, were partially blocked by fallen trees. Some flights in and out of New Plymouth airport were cancelled.

Near-record high extreme wind gusts for January were recorded at:

Location Extreme wind gust speed (km/hr) Date of extreme gust Year Records Began Comments
Mt. Kaukau (Wellington) 145 3rd 1969 Equal 3rd-highest
Gore 115 1st 1987 2nd-highest

• Fog

On the morning of 18 January, Wellington airport was affected by fog, with more than 20 outbound flights cancelled, and five incoming flights diverted.

Wellington city was affected by fog in the evening of 26 January, and on the morning of 27 January.

Fog closed Wellington Airport again on the morning of 29 January, forcing cancellations and delays.

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