Drier than average March ahead but rain possible
The Metservice advises that a front preceded by strong north to northwest winds will move north over the South Island during Tuesday, bringing a period of heavy rain to the west of the Island and the Alps.
The front should then weaken as it moves north onto the North Island late Tuesday and during Wednesday.
There is high confidence of warning amounts of rain in Fiordland overnight Monday and Tuesday morning, and in Westland during Tuesday.
On Thursday, the front continues to weaken as it moves over northern New Zealand , while a ridge of high pressure builds across southern and central New Zealand.
Weatherwatch report that we are now seeing some breaks with the huge highs that have led to drought in parts of New Zealand.
“As we head through March we start to see some 'gaps' between the highs - or put another way, areas of possible rain and showers between the long stretches of dry,” says a WeatherWatch spokesperson.
For January and February much of the high pressure linked together over the North Island in particular, leading to drought which continues to expand.
With forecasting what to look for in March, WeatherWatch advise that the best chance for rain is when one high departs but before the next high rolls in.
“This brings a period of departing humid sub-tropical northerlies and then incoming cooler drier southerlies - this can then start to spin a low in between these highs and generate some rain.”
The best chances for this appear to be around March 3 and 4, then again around March 9, 10 and 11 and March 13 or 14.
“These are "wet weather opportunities" for both main islands of New Zealand, giving some better optimism that we can see now. Not locked in - but showing up in the data at least.
“Extra long range, to the very end of the month, there are some signs that weeks three and four of March could see another tropical depression or cyclone to NZ's north - we are, after-all, heading into the peak of the cyclone season now as sea surface temperatures reach their peak. So nothing locked in - but 'watch this space' for late March,” says a WeatherWatch spokesperson.
“In a nutshell nothing jumps out as a "drought reverser" but unlike our last update in February we have slightly more optimism for wet weather.
“February was strongly about "droughts will get worse before they get better", but March looks more like the start of a balancing act - while still drier than average in many places we do see at least three chances of wet weather for many dry zones. Rainfall totals may not be huge but it's still a silver lining.”
A warning still exists around droughts.
“Drought zones may still increase, or local conditions may not improve a great deal in March for everyone. Fifteen day rainfall data suggests Northland may benefit from the more showery, humid, easterly but Waikato may not.
“In the South Island the hints of autumn may encourage more west to north west winds, encouraging a dry pattern to continue in Canterbury. As we're so used to, it's hit and miss relief - but hopefully a bit more hit and little less 'miss' in March.
“Overall, we are entering a drier than average month again but the difference is we have some rainmaker opportunities. It will still be a bit hit and miss and there will be still areas that get drier still.
WeatherWatch say that NZ has some better chances of rainfall than in February with possibly three opportunities over the next four weeks.
“Not all opportunities will bring a soaking deluge to your property - but the chance of rain in the region is lifting slowly.
“Based on feedback from our past three climate reports we're making a bigger focus on dates around potential rainmakers in the NZ area and a more detailed rainfall forecast over 14 days.”
“Temperatures can be a little more predictable than rain when it comes to long term, with up to 65 per cent accuracy that far out. The trend for March isn't surprising - with temperatures looking likely to continue to lean above average overall, due to no real southerly changes to clear the air - plus additional sub-tropical flows helping keep the humidity up.”