13 Feb 2019
Atmospheric circulation has been gearing towards drier conditions and there is potential for this to continue, and escalate, over the next few weeks across the region. Since Christmas, weather patterns have changed to a predominant anticyclonic flow to the west of New Zealand, pushing more westerlies our way. The sea surface temperatures over the Tasman Sea have been significantly warmer than average, creating a marine heat wave for the second consecutive summer. At the same time, westerlies have caused localised upwelling of colder subsurface waters on the Kapiti coast, contributing to stable and dry conditions over the region. The Equatorial Pacific remains very close to El Niño threshold, and so is also potentially contributing towards dry conditions. As seen on the first link below, the latest national drought index is showing very dry conditions on the Kapiti coast, and normal to dry around the Wairarapa. The extended weather forecast suggests that the second half of the month will likely continue to be dry. However, there has been tropical cyclone activity over the Pacific Islands and there is a slim to moderate chance that the region might be influenced by an incoming ex-TC by the end of the month.
Cumulative rainfall totals and soil moisture levels for the summer to date have been relatively high compared with recent years. However, the current dry spell and lack of imminent rainfall, has the potential to induce water stress across the region in coming weeks. Rivers are now falling below minimum flow thresholds and water use restrictions are becoming widespread.
For the latest national drought index state, please visit: (https://www.niwa.co.nz/climate/information-and-resources/drought-monitor)
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|