KEY POINTS:
The North Island and the South Island had two completely different weather patterns yesterday with high humidity and hot northerlies blowing across the North Island and cold southerlies across the South Island eastern and southern regions. Timaru peaked at just 13 degrees while 32 was recorded in Napier. Further north and Aucklanders sweated at sunrise with a balmy 23 degrees. Combined with almost 100 per cent humidity and an official high of 27 degree the humidex reading was around 39 degrees - and that's how hot it felt! This morning similar temperatures, around 21 with 99 per cent humidity.
The very friendly lady at my local liquor store (I thought some white wine might help me sleep!) was originally from Bangkok... we were chatting about how hot it was, with her fan blasting away, and she told me that this weather was exactly the same as Bangkok. Humid, damp, no air. This is why the humidex reading is so important to those in the north - just as the wind chill factor is important to us all in winter, especially the South.
The low spiralling out in the Tasman Sea is slow and - as I said on Monday - unpredictable. I think our new Auckland weather forecasts were very accurate and kept up to date with the ever changing system. Sub-tropical lows are often very difficult to forecast - especially slow moving ones like this one. I also mentioned, in reply to a comment about me sitting on the fence on Monday, about the "chance of precipitation". On Monday there was a 50 per cent confidence (that doesn't mean flip a coin ... it means there's a moderate chance of rain!). On Monday, the prediction for Tuesday was just 10 per cent. So MetService had periods of rain for Auckland, I believe, and we had overcast with drizzle patches and the odd light shower. For today, the chance is just 10 per cent again, but with less cloud about it's unlikely to be a wet day in Auckland. (Sorry for the Auckland focus for others around the country - I'm just using it as an example!). Tonight the percentage climbs to 30 per cent ... an indication that drizzle or very light rain may develop as the humidity lifts after dark. It's a helpful tool for us at the Weather Watch Centre but we don't always take it as gospel... it just helps with our confidence on predicting rainfall.
Humidity is set to stick with the North Island until Friday. On Friday the high in the southern Tasman Sea should gain strength and cover the country - giving us a mostly sunny and dry weekend with lower humidity. It also means Valentines Day is looking mostly sunny. (Don't forget our Valentines Day updates - each day - here)
But on Monday another low in the Coral Sea/Northern Tasman Sea area will drift down as that southern Tasman Sea high weakens again (highs often 'breathe'...growing and shrinking). This means another humid and wet start to next week. This is great news for farmers and those on rain water tanks - but bad news for those who have enjoyed a relatively humid-free summer and don't sleep well in the muggy conditions.
In the South Island the West Coast enjoyed 23 degrees yesterday while the east coast was much cooler. This week sees similar conditions with that cooler southerly or easterly flow continuing right through until Saturday - with some cold nights in the weekend too.
February is certainly proving to be a changeable month weather wise!
Philip Duncan
