THURSDAY, OCTOBER 20, 2016
NIWA's Hotspot Watch
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 are near normal for most locations for this time of the year, with wetter
than normal soils for this time of the year for most of the Gisborne and Hawke’s Bay regions. However, soils are
slightly drier than normal for this time of the year in southern Taranaki. The driest soils compared to normal for this
time of the year are found in far eastern portions of Wairarapa and Tararua.
Across the South Island, soil moisture levels are near normal or wetter than normal for this time of the year for much
of the northern, western, and southern portions of the island with the wettest soils for this time of year in and around
the Nelson region as well as from northern Fiordland to Central Otago. Soils are slightly drier than normal in
southwestern Southland as well as southwest Canterbury. From mid-Canterbury to far eastern Marlborough soil moisture
levels are much drier than normal for this time of year. The driest soils compared to normal for this time of the year
are found in coastal areas north of Timaru, especially in eastern Selwyn, Waimakariri, and Hurunui districts.
Note that the driest portions of both islands mentioned above have been dry for a long period of time, dating back to at
least last summer.
Outlook and Soil Moisture
For the North Island, weak low pressure will bring generally 10 mm or less of rain to most locations on Friday and
Saturday morning. However, Auckland and Northland will only see minimal rain from this event. Meanwhile, an easterly
flow will enhance the rainfall across Gisborne and northern Hawke’s Bay, where amounts of 25 to 40 mm will be common.
The interior ranges of these regions may see isolated rainfall amounts as high as 75 mm through Saturday night. Sunday
and Monday will be primarily dry as high pressure takes control. More showers will arrive on Tuesday, bringing 10 to 15
mm of rain to most locations. A few showers may continue across the western and northern North Island into Wednesday,
but these would only produce a couple millimetres of additional rain.
While official hotspot areas are unlikely to develop across the North Island during the next week, little relief is
anticipated for the dry eastern Wairarapa region. Rainfall in the next seven days is unlikely to be enough to reverse
the trend, and thus soils in this area will likely become drier. However, there may be slight improvement in the dry
portion of southern Taranaki during the next week.
For the South Island, a southerly wind flow will bring beneficial rain to the eastern side of the island today through
Friday morning, with amounts of 15 to 20 mm possible. Lighter amounts of 5 to 10 mm will fall in the rest of the island.
Dry weather is likely across the entire South Island during the weekend as high pressure sits overhead. However, the
next storm will deliver heavy rain to the West Coast on Monday and Tuesday morning, with many locations picking up 25 to
50 mm. As this storm moves farther east on Tuesday and Wednesday the eastern South Island may receive light rainfall,
but likely less than 5 mm.
Rainfall in the eastern South Island over the next week will likely prevent dry regions of eastern and northern
Canterbury from getting worse, and slight improvement may even occur. However, soils in far eastern Marlborough may
become a bit drier in the next week, although an official hotspot is unlikely to occur.
ends