June 2015 – everything but the kitchen sink
The first week of June saw bursts of heavy rain and thunderstorms for the northern North Island and Nelson, and severe flooding in Dunedin (3 June).
Several snowfalls occurred at higher elevations of both Islands (10-11 and 14-15 June), before a significant winter storm produced extremely deep snow for parts of Otago and Canterbury on 18-19 June. Following this major snowfall, a high moved in, resulting in a severe frosty period 23-25 June, nationwide.
Minimum temperatures in Central Otago were particularly savage over these three days,dipping to -21C. This significant winter storm also produced flooding in Hokitika (18 June) after more than 200mm fell in the township, and intense rain on 19-20 June caused problems from Taranaki through to Palmerston North.
Major flooding occurred in Whanganui after the river broke its banks, and a state of emergency was declared in Whanganui, Rangitikei and Taranaki.
Temperatures yo-yoed during June. The month started and ended unusually mild, but it was extremely cold through the middle of the month.
Record June rainfall was observed in a number of towns. Palmerston North recorded its wettest June with treble normal rain (274mm), while Dunedin experienced its second wettest June (154mm). Hokitika recorded its third wettest June (a whopping 448mm of rain!), as did Whanganui (236mm).
The Ocean
The 2015 El Nino continues to strengthen. Sea temperatures are now more than 2.5C above average off the South American coast, and continue in excess of 1C above average elsewhere along the equator (this is the El Nino 'warm tongue').
This is the strongest 'warm tongue' since the 1997-98 El Nino. Seas around much of the New Zealand coastline are now colder than normal, and this will influence (cool) our coastal air temperatures through winter and spring.
The Southern Oscillation Index (SOI) has bounced around over the last few weeks, due to local weather patterns rather than any change in the broad scale El Nino event. International climate models indicate further intensification of this event, with a high chance (85% probability) that it will continue into early 2016. El Nino typically reaches full strength towards the end of the calendar year.
The outlook – July 2015
Overall, more southerly winds than normal are expected over New Zealand during July, with spells of high pressure over the country. This means we are likely to see a "relatively" dry July, noting that July is traditionally a fairly wet month.
July precipitation is expected to be below normal for northern and western regions of the country, and near normal along the east coast of both Islands. After a warm start to the month, temperatures are forecast to plunge below average next week. However, temperatures should then move closer to average for the second half of the month.
Bottom line
Temperatures continue to swing, but end up near average overall. A drier than usual July is expected for most, with near normal rainfall forecast for eastern regions.
