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Weather Prospects for the Transit of Venus

posted Jun 4, 2012, 12:36 AM by Mike White   [ updated Jun 4, 2012, 12:38 AM ]
With less than 48 hours to go what are our weather prospects for D-Day?
I have been monitoring and saving the predictions for this Wednesday since last Wednesday. I have taken the images from each of the four main sources that I use to determine the weather for my location or any prospective locale if I have to travel to see an event such as this. The sources that I use are METVUW at Victoria University, the Met Service, Dr Ryan Maue of the US, and the U.S. Naval Met site FNMOC. The latter two only have low resolution for New Zealand but give a great indication of the overall synoptic situation.
After what for us in the Manawatu has been two and a half months of very settled weather I guess it was asking too much for that to continue past the first week of June! To describe the current weather as un-settled is putting it mildly. This therefore makes the art/science of long and even short range weather forecasting not something for the faint hearted. I have saved the forecasts on a daily basis. Some of the sites put out more than one scenario a day. The unfortunate thing for those of us trying to make big plans for Wednesday is that every forecast has been different enough to cause doubt about any would-be plan for the day. At 48 hours out however the two main forecasters with detail on New Zealand that we use are coming closer to agreement.

Transit of Venus Weather Predictions

The files attached have a date stamp in U.T. on them. The transit starts at 10.30 a.m. N.Z.S.T. = 2012.06.05 22.30z, so the nearest chart to that time is the one for noon on Wednesday the 6th, or 2012.06.06 00z, the "z" standing for hours U.T. Attached are the views for the South Pacific and the North Island from METVUW and the whole of New Zealand from the Met Service as of this morning. I have put in 4 of the most relevant images from the Met Service who have pics for every three hours on the day.
The top half of the North Island: The Coromandel and northern B.O.P. may have broken cloud situations that will give them some hope initially but things look to deteriorate throughout the day!
Taranaki: Northern parts including New Plymouth and across the central plateau to East Cape look to be wiped out through most of the day. Local knowledge will come to the fore with regard to there being any chance of finding a leeward hole in the clouds downstream of the Mountain.
East Coast, Poverty Bay & Hawkes Bay: Both METVUW & the Met Service show this area to be the best opportunity of seeing anything in the N.I., especially early on. J.D, J.B. & Graham Palmer expect phone calls tomorrow night! I know the Hawkes Bay Astronomical Society will be setting up at the Hoult Planetarium. Those of us from further south could be joining them. However the Met service’s written brief for these locales do not look as favourable. We will have to wait and see.
Wellington & Wairarapa: Both met sites suggest that the chances of seeing the sun from there are less than 5%. Say no more! A cold southerly arriving in the afternoon will ensure a complete wipeout.
Manawatu & Horowhenua: The wind direction says it all really. West to Nor West = cloud. For the Kapiti Coast and Horowhenua it also = rain!! We will be traveling. Most likely over to Napier or further if we have to.
The South Island: As can be seen from the charts the top half all the way down to South Canterbury looks to be bearing the brunt of the bad weather on the day. Jessica Cullen our (P.N.A.S.)  most southern member in Dunedin may have a better chance of seeing the whole event, even if she maybe surrounded by snow?!
The Deep South: Met Service shows a southerly (although their written brief says westerlies) for Bob Evans on the coast at Invercargill. It may be better inland in a sheltered area.
Just a reminder that these charts do NOT show cloud but rain. Where there is no colour doesn't mean clear skies. Conversely with the METVUW charts where it shows an homogenous spread of colour doesn't mean that it is wall to wall cloud either.
It is only one of the rarest of predictable astronomical events, one that no one alive now will be able to partake in again. So by Murphy's Law we should have expected this type of weather from the outset. Speaking of Murphy's, if it gets even worse than this that's where you'll find me drowning my sorrows.
Sincerely wishing you all clear skies,
Ian Cooper