A weekly update describing soil moisture across the country to help assess whether severely to extremely dry conditions are occurring or imminent. Regions experiencing these soil moisture deficits are deemed “hotspots”. Persistent hotspot regions have the potential to develop into drought.
Facts: Soil Moisture
Across the North Island, soil moisture levels have generally decreased since this time last week. Substantial decreases were observed in the East Cape, western Bay of Plenty to southern Auckland, and along the east coast in the Central Hawke’s Bay, Tararua, and Masterton districts. Smaller decreases also occurred in much of Northland, Bay of Plenty to Hawke’s Bay, and Wellington. Meanwhile, small increases in soil moisture levels were observed in northern Manawatu-Wanganui, eastern Taranaki, and southern Waikato. The driest soils across the North Island compared to normal for this time of the year are found along the coast in the Central Hawke’s Bay and Tararua districts, while the wettest soils for this time of the year are found in the northern Coromandel Peninsula, central Bay of Plenty, and much of Wellington. In the North Island, hotspots are now in place in coastal areas of Central Hawke’s Bay and Tararua districts and in the East Cape.
Across the South Island, soil moisture levels have generally not changed significantly since this time last week. However, soil moisture levels did decrease in coastal Hurunui district, where a hotspot is now in effect. Other small decreases were observed in northern Marlborough, Nelson, and central Canterbury. Meanwhile, increases in soil moisture levels were observed in southern Canterbury, much of Southland, and along much of the West Coast. The driest soils in the South Island compared to normal for this time of the year are still found in northern Canterbury, while the wettest soils for this time of year are found in coastal Otago.
Outlook and soil moisture
For the North Island, a few showers will move across northeastern areas today and on Friday (2nd December), bringing as much as 10 mm of rain to regions such as Bay of Plenty, Gisborne, and Hawke’s Bay. However, little if any rain is expected elsewhere. An odd shower or two will be possible on Saturday and Sunday, but any rainfall would be minimal. Isolated showers may occur in central and southern areas from Monday to Wednesday (7th December), but rainfall totals there will likely be 10 mm or less.
With low rainfall expected across much of the North Island, soil moisture levels are generally expected to decrease in the next week. This will likely lead to an expansion of the hotspot located from southern Hawke’s Bay to the northern Wairarapa, and the hotpot in the East Cape may get slightly stronger as well. While no official hotspot is expected, drier soils will also continue to develop from western Bay of Plenty to southern Auckland.
For the South Island, a few showers will move up the east coast tonight through Friday (2nd December), generally producing 5-10 mm of rain in Canterbury, and isolated amounts up to 15 mm. A few light showers will be possible on both Saturday and Sunday, but rainfall totals will likely be no more than 5 mm. Showers along the West Coast on Tuesday (6th December), may produce up to 15 mm. On Wednesday there is the chance for a storm to bring significant rainfall (>25 mm) to the West Coast, but eastern areas would likely only receive a few millimetres.
With generally low rainfall amounts expected in the eastern South Island, the hotspot in coastal Hurunui district will likely strengthen and may extend south into Waimakariri district. However, no other hotspots are expected to develop.