Tuesday, 11 December 2018

Passage planning - Weather

Squalls on the way to Tuvalu two years ago (Victoria photo)
INTRODUCTION

Our next planned passage is from Fiji towards Majuro.  Since we are far behind our intended schedule we will try to do it in one single passage but keeping options open for a stop in Tarawa if it appears prudent.  The passage is about 1600 nm down the rhumb line, starts in an active cyclone zone, crosses two convergence zones and two tradewind belts so there are some complexities.

We have been asked in the past how we assess weather windows so here is a brief blog post on how we look at the weather to decide when to go.  In a later post I will address how we look at navigation preparation.

STRATEGIC VIEW

As we plan our seasons we first consider how to avoid tropical revolving storms - cyclones in the South Pacific or what we would call hurricanes at home.   We try to not be in the cyclone zone during the season (rather unsuccessfully this year).  Like most things in nature, the "season" does not have a strict start and stop but rather increasing and then decreasing probabilities of cyclone formation.

From there we look at the likely winds and other conditions to be encountered along the desired route.  There are various sources for this:
  • Pilot charts - These are available for free from the US Government and show the average winds and directions and ocean currents as well as probabilities of gales or calms for each month of the year.  Open CPN also has a great plug-in to display much of the pilot chart data overlaid on your charts.
  • Jimmy Cornell's Ocean Atlas - This is a commercial product we have that is a refinement of the government pilot charts specifically for crossing oceans by sailboat. 
  • Noonsite usually has good country by country weather information as well.
  • Finally, we look at the previous year's weather with some historical grib data.  With qtVLm we can even simulate doing the route using actual weather data.
A zoomed in portion of the pilot chart.  The red arrows show our start and intended finish locations.  The blue circles with spokes show the average winds and directions while the green arrows are the average currents.


The same data but overlaid on Open CPN.
The degree of analysis depends on our assessment of the risk.  If we are heading downwind in the trades in the cruising season such as our recent sweet run from Tonga to Fiji we will not do much research.  This upcoming passage receives a bit more analysis, and the potential trip to Alaska next year receives a lot of consideration !

TACTICAL

As the desired departure time draws closer, it is time to start watching the weather patterns.  Again,  the perceived level of risk drives how soon we start and how hard we look.  Generally for the bigger passages we try to start a month ahead to get a feel for the weather patterns.
 
To "watch" the weather, we primarily use GRIBs downloaded over the internet if feasible/available or on our Iridium Go.  Depending on the area we are hoping to sail through, we also use weather maps or weather faxes to give us a better understanding of what is going on.  These maps are produced by the national meteorological agencies and are produced by actual meteorologists rather than just the output of a computer model like the GRIBs.  They are also labelled making it easier to understand where the frontal systems and convergence zones are located.

Fiji Met provides nice Analysis charts but unfortunately do not provide the synoptic charts showing the forecast conditions.

We download and view GRIBs with Predictwind Offshore.  We have used a lot of different software packages over the last almost ten years (over six in Fluenta and then STV Tuna prior to that) but Predictwind Offshore has been our favourite over the last two years.    It gives access to:
  • Four different weather models: the usual GFS model and the European ECMWF model, as well as two proprietary Predictwind modes.   We find having multiple models gives us an insight into the reliability of the forecast (i.e. do the models agree?) and shows multiple possible outcomes so we can get a heads up if there is an increased possibility of something unpleasant occurring.  While the GFS model is free to the public, the ECMWF model is only available through paid services such as our Predictwind subscription.  In our experience this model has been the most reliable in the areas we have been sailing.
  • Wind and Waves.  Wind is of course rather important to a sailboat but it is the waves and their direction and period that can make us really miserable!
  • Convective Energy (CAPE or convective available potential energy):  CAPE is an indicator of the instability of the airmass.  We find it useful as an indicator of the location and intensity of the convergence zones.  If you look at the winds in a convergence zone, you will notice that light winds are forecast.  The reality though, is usually mostly light winds interspersed with significant squalls and electrical storms.  Not really fun sailing or motoring!
  • Currents - Beyond the effects of the tidal streams, there are significant ocean currents swirling about on the open seas.  Even a 0.5 kt current makes a significant impact when you average 6 kts boat speed. 
  • Precipitation - At first it may seem like this is a funny thing to be concerned about, but the rain forecasts are a great way to see where the frontal systems are expected to be.  While weather faxes have the fronts drawn on them, the GRIBs do not show the frontal systems.  With the rain forecast data, the front locations can be inferred.
  • Routing - For long passages I used to look at the weather along our desired route by marking our expected locations for each day using our average daily runs and then using a spreadsheet to record what winds we could expect at those times and locations.   This is far less tedious now with the routing function on Predictwind Offshore.  I input the start and finish positions, set our minimum winds before switching to motoring, and press "download".  The routing is then done on the Predictwind server using the highest resolution wind, wave and current data and the end results are sent back to us in a small file (approx 6 kb) .  The forecast weather data and expected boat speed, direction and location can then be viewed on the chart, in tabular form or on a graph.  I have not done a "how to" on this as it is covered in the Predictwind website far better than I could ever do.
Here is a screenshot of the forecast winds according to GFS along with recommended routings based on the four weather models.  Looks like nice light sailing near Tuvalu until you look at the next chart.

From the CAPE data you can see that significant convective activity is forecast in the same area.  In this case it is the South Pacific Convergence (SPCZ).

Here is the ocean current data.  The HyCom model, associated with the GFS wind forecast, is shown  here.  The light green area at the green boat (GFS routing) is forecast to have 1.7 kts of current.  That is a nice boost with a boat speed of 6 kts.
For more complicated routes we also have used a weather router.   Our favourite weather guru is Bob McDavitt or Met Bob.  He is very knowledgeable with an excellent understanding of the South Pacific weather after decades covering the weather of this area.  He is also very affordable and you can tailor the services based on how much support you want.  We have used him for six passages between the tropics and New Zealand and our last trip from the South Pacific to the Marshall Islands and back. With any router it is important to do your own assessment first so you can look at the recommendations with a critical eye.  Further, you should be cognizant of the time delays in working with a router i.e. the data the routers use for their assessment may be quite dated by the time you actually download the email.  This is another reason you need to be able to download your own data and do your own routings and risk assessments in a timely manner. So, does one need a router ?  Absolutely not, but it is another tool to help increase the probability of a good passage.  It is also nice to have a router available if you have a problem or the weather does not cooperate.  The router is sitting in a dry stable office with real internet, a big screen, years of experience and is not likely to be sleep deprived or sea sick.

Me with Met Bob a few years ago.
ENROUTE

Finally, after patiently waiting for a "good enough" window you are at sea on passage.  Whew.  Once underway I download weather twice a day.  With the Iridium Go and unlimited data, we can be a lot more greedy downloading weather data than we were when we relied only on the SSB radio.  The routing is analyzed back at Predictwind's server so it is done with the best available data. Even so, it is nice to have an overall picture so we download the forecast weather for the remaining time of the passage as well.  The ocean current data is quite data intensive so it is nice that the ocean currents are incorporated into the routing.

Keeping up to date with the weather allows us to, at a minimum, mitigate the effects of undesirable weather.   We can try to avoid winds that are going to be too strong or too light.  In areas of forecast calms we can decided whether it is better to drift, sail slowly or motor, depending on what is forecast to happen after the calms or where and when the winds will fill in.  In the the tropics we will normally continue to sail as long as the sails are drawing.  Conversely, between New Zealand and the tropics, if the winds are calm it usually means the weather is just taking a break before it gets awful, so we will motor to maintain a minimum speed and reduce our risk exposure.

Arriving in New Zealand.

The forecasts also allow us to look at options for diversions.  For example, earlier this season sailing from New Zealand to Tonga we were mentally committed to pushing on to Tongatapu regardless of the headwinds.  However, when we looked at our options, it was clear that a diversion to Minerva Reef and two good nights of sleep anchored there would allow for better weather on the way to Tonga and only delay our actual arrival into Tonga by one day.

If the conditions are not matching the GRIBs we also have the option of contacting our weather guru to get his take on the weather.  We also can use the weather fax or download the Fleet Code to get another view.

Finally, do not forget about the old school methods of looking outside, Buys Ballots law and checking the barometer !

and sometimes it is just nice to be in the calm at anchor.  Here we are in Tuvalu two years ago.


Monday, 10 December 2018

Belated 50th Anniversary Trip to Fiji Adventure


The crew at the ever lovely Paradise Resort
It was not practical to fly back to Halifax for Liz's parent's 50th wedding anniversary so it was nice they could fly out to Fiji to join Fluenta Cruise Lines for a three week adventure with us.

Liz took a taxi up to Lambasa to pick them up and deliver her parents to Fluenta at the Copra Shed in Savusavu.  We spent a few wet days in Savusavu (1 on the cart below) before heading out.

We had never been to Dakuniba Bay (2) before and it was within a day's sail of Savusavu so that was our first destination.  We anchored in the very sheltered bay of Nasasobu right in front of George's house.  George's grandfather was a successful boatbuilder and sailor who settled his family in the bay when George was a baby. He hosted us ashore and we were delighted we could host his young family onboard Fluenta for dinner one night.  Of course, we dingied into the neighbouring village in Dakuniba for sevusevu and then back again the next day for church.  According to some of the ladies we were the first kaivalagi (white folk) to attend the church in their 20 year's of going to the church.  As often happens, we were hosted by a family before church and then invited to a feast afterwards followed by a yaqona session.

A few days later we took the rather tight inside route - between the island and the barrier reef - around to anchor off Dolphin Bay (3) resort to visit ashore (our first time there in 11 years) and to go snorkelling. And drink more kava ...

From there we went to the lovely Paradise Resort (4) on the south tip of Taveuni for the much belated 50th Anniversary celebration.  We had a relaxing few days there enjoying the nice resort, the excellent staff and great food.

Finally, we sailed back to Savusavu.

A screenshot from our Predictwind Tracking page showing the trip with Liz's parents: (1) Savusavu, (2) Nasasobu, (3) Dolphin Bay, (4) Paradise Resort.
Liz's parent arrived and were quickly put to work.  Here Johnathan and Wendall install Liz's much anticipated Lee Valley magnetic knife rack.

Wendall lying down on the job again.

and supervising Johnathan's cutting

Still some time for chess

and checking out the pearl farm

and the local market.  This is our friend Lisey from Tuvalu.

And, of course, eating at Arun's Taste of Hidden Paradise !

The entrance to Dakuniba and Nasasobu.  Note that the charts are off by about 600 ft - the red route is what Navionics and C-Map show as the entrance. You can also see the inside passage to Viani Bay to the south.


A day's sail away from Savusavu makes such a difference.  We anchored in the very protected bay at Nasasobu and were welcome by George and his family.

George was an amazing host.  When he heard that the kids love fruits he made regular deliveries from their extensive plantation.

We were so glad we could have his family over to Fluenta for dinner.

Dinner onboard Fluenta.

George's uncle, David, showing us lemon grass for tea with Fluenta anchored in the background.

Heading ashore to do our Sevusevu.  The Sevusevu is the Fijian traditional ceremony where one asks permission to visit a village through the presentation of kava.  We make sure we sevusevu whenever we go to a new village.  While some cruisers begrudge the tradition we actually like it as it provides a great opportunity to meet the key people in the village and ask lots of questions.

Sevusevu with the chief at Dakuniba

Not the easiest commute. A long walk through the mud flats from the dingy to the village.

Benjamin post-sevusevu in the village.  Johnathan, Benjamin and I have sulus for church and sevusevu.


We went back into Dakuniba for church the next day.  We were quite early so Ilitia invited us to his house to rest before church.  The villagers were fascinated with Jean's knitting.

and they kept us well supplied with coconuts.

and more coconuts.

of course, while we were lounging around the ladies in the village were cooking.

After church, we were invited back to a feast celebrating a baby's birthday.

After church, we were invited back to a feast celebrating a baby's birthday.

and a bigger audience for the knitting

While Liz and the ladies did the dishes.
 
while the men hung around and drank kava.




After Dakuniba we moved further along the island through the inside passage to Dolphin Bay Resort.  This is a not a village but rather a resort so no sevusevu is required.  We still drank some kava though !  Liz and I stayed here 11 years ago when visiting my parents for the first time in Fiji.

Kava time.


Fancy breakfast onboard with real maple syrup brought in from Halifax (funny story to the syrup as much of the text is in Arabic - A Nova Scotian syrup producer - Hutchinsons - was put into a rather "sticky situation" during the diplomatic row between Canada and Saudi Arabia as a massive order was cancelled.  Nova Scotians rallied and bought up the whole order.  Now one of their bottles is in Fiji and on its way to the Marshall Islands)

A belated celebration of their 50th Wedding Anniversary.  Sonny, one of our favourite characters at Paradise Resort, "borrowed" this sign from table setting for some actual newly weds staying at the resort

More amazing food at Paradise.

To celebrate Johnathan's birthday we of course went dingy surfing.


Final dinner at the Captains Table at the Copra Shed after a nice tour of the islands.
Fluenta moored off Paradise Resort.

Sunday, 9 December 2018

Return to Savusavu

We had a great passage to Fiji from Tonga.  We cleared into Fiji at Savasvau where, as usual, everything went smoothly.  We treated ourselves to a spot on the dock and started getting some "on the dock" projects completed and prepare for visitors.

Liz's birthday was on passage.  Not sure I would approve the lit candles on passage again ....


And then after we arrived it was Victoria's birthday !

A photo Johnathan took at the Botanical Gardens.

Emptying the V-berth for re-organisation.

And doing the 3 year service on the windlass.

Johnathan designed and is building a replica gun.

While I hung out in the lazerrete inspecting the steering, autopilot, heater etc.

Topping up the diesel tanks.

Some school (but I am not sure every kid uses a beer bottle box to write on)

Oops.  A quick trip to the hospital after Benjamin fell off a several foot high kerb.  Arun, the owner of one of our favourite restaruants - Arun's Taste of Hidden Paradise, shut down the restaurant and drove us to the hospital.  Later that night he and his wife drove to the hospital to give us a ride home ! Such nice people.  When we later had to leave Savusavu sooner than we had intended they dropped by the marina and gave us some delicious food to bring us for the passage.

We have been looking at what we will do when we get to Victoria.  As we are finding out, getting a berth in a marina as "liveaboards" is not easy.  Turns out our new neighbours, SV Sombrio, lived aboard in Victoria for seven years and provided usa lot of insights (and a recommended marina - fingers crossed we get a spot !...)

It rained.  And rained ... Victoria setting up our rain catching as the town's water was contaminated and the harbour was too murky to run the watermaker.

It made for the Copra Shed a great place to play tag though !