This webpage provides a brief summary of climate and hydrological conditions in the region. This service is only updated during periods in which closer monitoring is required (regardless of time of the year), in recognition that we are in a dry spell of weather. It does not define an official council position on drought or drought declaration.
A dry spell remains over most of the country and has potential to worsen. Most of the North Island and the north-eastern part of the South Island have been very dry. The national drought monitor index shows that Northland and Auckland are classed as having a severe meteorological drought, and MPI has declared this an adverse event for Northland.
For the Wellington Region, even though the situation is not nearly as severe as for Northland, the entire region is now classed as dry. The Wairarapa is classed as between very dry and extremely dry, according to the national drought index. Currently, there is no forecast of significant rain for the region until the end of the month, and so the dryness has potential to escalate.
The main climate influencers (i.e. “climate drivers”) such as ENSO (El Niño – Southern Oscillation) and Indian Ocean Dipole (IOD) are currently neutral, and therefore having little bearing on the evolution of the summer pattern.
The Southern Annular Mode (SAM) has been systematically on the negative side over the last few months. This climate mode helps explain the unusually strong south-westerly flow that has persisted from late spring into summer. Strong winds promote evaporation, and are a contributing factor to drying the exposed soil.
The westerly pattern is also preventing the formation of summer thunderstorms and moisture input from the subtropics, which would normally manifest during north-easterly flow this time of the year, when the sea surface temperature is sufficiently warm.
Air temperatures for the first half of the month are up to 2oC above average for most of the region, which is further contributing to increase the dryness.
Even though the region had near normal rainfall for spring, and above average rain in December in the west, the hydrological year accumulation (i.e. Jun to May) to date, and the overall dryness, are comparable to previous dry years.
River and stream flows have been receding through January and early February with only small and short-lived interruptions from one or two fresh flows from rainfall. In the west (Kapiti Coast and Hutt Valley) rivers are reaching mean annual low flow conditions but are already well below this in the Wairarapa.
Preliminary indications are that flows in the Wairarapa have already fallen to levels that are only expected once every five years (on average) and moving towards 10 years in some cases. Restrictions for water users are now in force across all catchments in this part of the region. With no significant rainfall in the near term forecast some fairly extreme low flows can be expected.
How different has recent rainfall/soil moisture been compared with the same time in previous years?
Click on the links below to see the relevant anomaly map
|Kapiti Coast (lowland)||Otaki at Depot|
|Kapiti Coast (high altitude)||Penn Creek at McIntosh|
|Porirua||Horokiri Stream at Battle Hill
|Wellington City||Kaiwharawhara Stream at Karori Reservoir|
|Hutt Valley (upper catchment)||Hutt River at Kaitoke Headworks|
|Upper Hutt||Upper Hutt at Savage Park||Upper Hutt at Savage Park AQ|
|Wainuiomata||Wanuiomata River at Wainui Reservoir|
|Wairarapa (high altitude)||Waingawa River at Angle Knob|
|Wairarapa Valley (north)||Kopuaranga River at Mauriceville|
|Wairarapa Valley (Masterton)||Ruamahanga River at Wairarapa College||Wairarapa College AQ|
|Wairarapa Valley (south)||Tauherenikau River at Racecourse||Tauherenikau River at Racecourse|
|Wairarapa (north-eastern hills)||Whareama River at Tanawa Hut||Whareama River at Tanawa Hut|
|Wairarapa (south-eastern hills)||Waikoukou at Longbush||Waikoukou at Longbush|