07 January 2014

Weather Forecasts. The Good, the Bad and the Ugly.

I have quite a bit of catching up to do in terms of posts, sorting out photos and videos of the trip, etc. I have also decided to do a few posts about things related to but not directly concerning the trip.

This one is a bit of a rant.  Be warned.

If you're a sailor (and I am one, so I know) then marine weather forecasts are critically important for your way of life.  In some cases, the correct marine weather forecast may decide whether you live or die.  So forgive me for being a bit brutally honest here.

This is the official website of the Australian Bureau of Meteorology:  http://www.bom.gov.au/ -- it gives a map, some major city day forecasts, and a set of large clickable (OK, butt ugly, but easy to find) buttons down at the bottom.  One of those buttons is marked "Marine".  That button takes me to a page sorted by state, and I can click on the "Local and Coastal Waters" forecast on the NSW tab, go to a map of NSW and see a map of sea areas.  The Hunter sea area is clearly shown on the map.

At sea, sailors tend to have very limited internet access.  They either rely on mobile phone connections that tend to drop in and out, or they rely on satellite phone, or they rely on VHF or HF weather forecasts.  Fortunately, I can tune my VHF radio to channel 16 (the standard calling channel) anywhere on the NSW coast, and hear a weather forecast broadcast approximately hourly.  If I am in the vicinity of the Hunter region, I will hear a weather forecast that commences with "Hunter, between Seal Rocks and Broken Bay, and 60 nautical miles seaward" (I have heard this forecast so many times I have the litany committed to memory).

This is the official web site of the "Meteorological Service of New Zealand Ltd" -- it's not really obvious from that name weather it's an official government bureau or whether it's a company that happens to provide weather forecasts, but oh well, this is the one I stumbled into:  http://www.metservice.com/national/home

When I hover my mouse over an area on that page (grrr ... hover over links often don't work with limited bandwidth) I see a sort of map thingy with sea areas marked on it.  Perhaps I don't see the map and just see a list of sea areas.  If I can't get the map up then I can listen to VHF channel 16, or maybe 21 or 22 (channels seem to vary up and down the coast) and hear a weather forecast for "Conway".  A friend of mine who happens to be familiar with the coastal regions of NZ says "well that must be the area off the Conway river in Canterbury".  Myself, as a visitor to NZ, I have no way of figuring out what area "Conway" is.  In fact, I passed through three areas of NZ coastal waters, listening to or attempting to fetch the forecast multiple times without really knowing what those areas were called.  None of the cruising books or guides I purchased gave a list of these areas.  There were no broadcasts of what these areas were on the VHF stations, and I finally resorted to calling Marine Radio Wellington on VHF 16 to ask what weather zone we were in (at the point of hearing a gale warning on the radio I figured it was best for us to know whether that applied to us or not).

So, between Nelson and Lyttelton we travelled through 3 sea areas.  We received, over a period of time, a total of 5 weather forecasts for those areas.  None of those forecasts gave either the correct wind direction or speed for any part of those areas that we travelled through for any part of the day in which we were travelling.  The forecast for day 1 leaving Nelson was for light south westerlies, we got strong north easterlies.  On day 2 we were forecast strong south westerlies and heavy rain -- we received light north westerlies and sunny conditions.  Sailing down the east coast we were forecast westerlies and got northeries, then we were forecast north easterlies changing to north westerlies and got north westerlies changing to south westerlies.  None of the forecast wind strengths were accurate (forecasts can be out by 40% in gusts, we assume this, but the forecasts were frequently out by 100% or more).  It was as if we were sailing in one country and receiving weather forecasts for a different country.

Yes, I know NZ weather is changeable.  I know it can be patchy in places.  However, at one point (just south of Kaikoura) we were hit by a southerly front.  I could see the frontal clouds approaching for a few hours before.  I speculated how much rain would be involved.  I suspected that the winds would turn sharply south west, and intensify.  This was information I gathered by looking out the window at the clouds.  Apparently, the Meteorological Service of New Zealand Ltd doesn't have windows, because they were unable to predict the front.  A southerly front (northerly front in the northern hemisphere) is the easiest weather system to predict -- it is preceded by high cirrus clouds and contains a band of strong winds and rain followed by clear, windy, cold weather.  This is basic high school science project weather forecasting.

The marine weather forecasts I was given seemed to be wind averages over a 12 or 24 hour period.  This isn't really suitable as a coastal weather forecast, and in an area with winds and weather as changeable as the coastal regions of the South Island of New Zealand, it's not really a useful forecast at all.

At various stages of the trip I was downloading GRIB data.  These are digital weather forecasts that can be overlaid onto an electronic marine chart.  The GRIB files I were using were supplied by NOAA, which is a US weather agency.  The data in those files was significantly more accurate than the marine weather forecast given by the NZ met service web site or by the VHF marine weather broadcasts.  At this point I have to question the existence of the NZ met service -- if an overseas agency can provide data significantly more accurate to local conditions than your own data, then why do you provide your own data?

So, there are clearly some things that need changing in the NZ marine weather forecasting system:
  • Make the web site actually navigable, paying attention to potential users of that web site (sailors who may be some distance off shore while navigating the site).  A useful mobile site might be of some use.
  • The weather forecast zones are clearly too large.  There was no relationship between the "Conway" weather north of Kaikoura and the "Conway" weather in Pegasus Bay, they should obviously be separate weather zones.
  • Make the weather zones known to users of the service, include the description of the zones in the weather broadcasts, and include a guide to the weather zones in some way accessible to sailors visiting NZ for the first time.
  • Make the weather forecasts themselves more granular.  If it's known that a southerly front with winds around 35 knots is going to pass through a weather zone around 4pm then include this information in the weather forecast, not just give a rough overview of the average winds during the day.
  • Stop smoking whatever it is you're smoking and give some forecasts that are approximately correct at the very least.  If NOAA can get it right then the met service should be able to get at least close, considering that most of the same data is available.
OK, end of rant.  In general, sailing the NZ coast was a generally pleasant experience, in spite of the efforts of the met service.