Saturday, 24 January 2015

VOR 2401 - one and in...

The fleet as expected hit the coast, must be an absolutely stunning part of the world to race up...

The 1240z posreport shows DFRT with a significant loss over the last 6 hr, but still with a handy lead dead upwind of the fleet. Distances are to a mark approx where they will leave the coast.
1240z posreport

Optimal routing shows a very definite track for the fleet. Stepping offshore and a final tack to then being freed up all the way in. Shaded is a 60min sensitivity to the route for DFRT. Winds 0.25 deg GFS. Ocean and Tidal Currents from www.tidetech.org
0.25 deg GFS model
Results to SANYA - times UTC
Results are as expected. Not many opportunities exist. Options for the chasing pack are:
  1. Tack on DFRT line, and grind them down on Bsp only
  2. Tack with DFRT, therefore cutting the corner slightly and reducing miles sailed
  3. Go beyond DFRT line in the search of a slightly better angle in
Will be very interesting to see how this is played, and each team will have a different feel for it depending on their preferred angles and strengths. Go wide and hope for an increase in pressure? Go early and have a better angle in lighter airs? My polar suggests the peak speeds for the boats in 14kt TWS is between 110 and 120 TWA. Either side of that and Bsp drops quickly.

Wind fields suggest slightly better but headed pressure for the last 100nm in E and much lighter and lifted in the W. A very quick assessment looking at the GFS 0.25 suggests if you wish to get some leverage then get further W of DFRT, however will bleed miles very quickly as DFRT point at the mark. No consideration here for the best angle to approach the Island/finish.

An ensemble run using the GFS control and perturbations, the shape of the route remains the same, however it shows the options for timing of the course change to the N. A good mean cluster with only a few outliers.
GFS Ens control and perturbations
Current is still a factor, however will be the same for everyone and no alternative options seem to exist.
www.tidetech.org

And finally, a video of the run...



Friday, 23 January 2015

VOR 2301 - its been a while...

As the boats ease out into relatively open ocean after the confines of the straights - the collective sigh could be heard from here.

Looking at the 0040z position reports, still a very tight pack but DFRT is getting a little richer...and barring any failures (lets hope this is no jinx), if they play it smart then they should be able to defend.

A nice little gain in the last 6 hr over the fleet and back out to a 50nm lead. Reference mark is off of the E coast of Vietnam.

Optimising in Expedition the results speak for themselves (results are to Sanya)

Fleet routing GFS and TideTech


Although clear of the straights, this is possibly not the last the fleet will see of the coast...running the route with GFS 0.25 degree from saildocs, and currents from the Tide Tech tidal and ocean current forecast model shows the pack hitting the shore. What will SCA1 do?








Route only partly influenced by the current model up at around 10n.
Currents - Vietnam coast




















However, this route is relatively sensitive irrespective of currents - viewing a shading of a single run where shaded area shows a loss of no greater than 3hr when diverging from the optimal route - pretty insistent to stick to the optimised route. RED is a run without current, BLUE is with the current included
BLUE route run with currents

An animation...


Tuesday, 6 January 2015

VOR 06/02 - time to leave these shores...

Seems a relatively intense period for he fleet, 3 days of yet again measuring metre by metre gains and losses. I've been keeping an eye on progress, waiting for a move off the shore, and by all accounts it is about now that the fleet should start to take a right turn.

It looks like DFRT have been itching to head off, but the fleet bounced back to the shore at about 0830z and DFRT very smartly covered them. If the fleet had stayed then I'll bet DFRT would have kept going.

Running optimisations in Expedition starts to paint a picture of what the future holds.

Results

Reference point for results distances is wpt at the southern tip os Sri Lanka. It appears the VOR tracker is using a very similar waypoint.
Results
Results are from a run using GFS at 0.25 deg resolution, and using TideTech ocean and tidal current forecast, with the finish at Pulau We...still a long way to go from there...


Routing

Showing a drive to get offshore...
Using 0.25d GFS and TideTech

Laccadive Sea

The transit across the Laccadive Sea will pose some challenges - with some significant wind accelerations and very significant currents
GFS wind - 11 Jan 21z
TideTech current - 11 Jan 21z

The Bay of Bengal


The forecast would possibly change radically from this run - as looking at alternative models shows a significant anticyclone to deal with....this will make next week interesting to say the least.

Optimal routes are run with GFS - so the routes on GEM image below are not relevant...
GFS

GEM

Friday, 2 January 2015

VOR 02/01 - Leg 3 overview

This leg is relatively straight forward in terms of strategy, as the route is quite confined geographically. However options exist to let MAPF split and go their own way again...

My guess is the fleet will once again play it very safe and stay in contact and work on eking out metre after metre on their competitors.

As has been proven over the first two legs, anyone who splits becomes vulnerable and runs the risk of getting dropped. It is very difficult to stay at 101% performance out on your own, that is why the huge expense of two boat testing has proven time and time again to give value for money over one boat sailing and measuring data. Some things just cannot be measured virtually.

Once out on your own,  priorities: primary... focus on your own metre by metre performance gains and secondary... overview of routing/strategy options....can change places...

Here is a historical routing run with 35 years of 0.5 deg ECMWF reanalysis data since 1979. This does not represent options available on this leg, it shows the historical variations in routes run from 1000z 03 Jan 1979, 1980, 1981...etc.

A very real pattern emerges, however the high road or the low road from Sri Lanka to the straights can throw up some options.

Drag racing

High road or the low road - what will MAPF do???

An unpleasant part of the world to race through
Glad I'm not there - nice one Phil!

Averaged wind data for the 35 years of runs...

And...for this leg, here is a run with 0.5 deg GFS. The model is only out 16 days so stops just after Singapore. However the route is run to the finish with the last wind field in the model - plenty of pressure to be seen.

...and the route output. What is interesting here is the very high % of time spent in very light airs seen out of the gulf, approaching the straights and through the straights...this could well be an anomaly in the routing output however have not dug too deep into it so have left as it is...

Tuesday, 16 December 2014

Learning from the mistakes of others

Volvo Ocean Race is setting up an independent inquiry into the Vestas incident in Leg2. See release here

There are a large number of factors to consider in this report. I for one will be very interested to read the outcome from a technical and a human perspective.

A very undesirable outcome of this report may be new rules/legislation to go some way to prevent this from happening again - i.e. creating exclusion zones around land masses, or external/third party intervention.

This is already evident in races that now have restrictions/limits in place for ice, drastically changing the way oceanic races are run. Having experienced the over cautious and at times in my opinion ill conceived constraints placed on long Southern Ocean legs, the last thing adventurous races such as this require is more restrictions.

Also seen is the navigation restrictions placed at some large international regattas preventing well prepared and knowledgeable yachts from taking advantage of their research and knowledge. Les Voiles de St Tropez and some events run by YCCS in Porto Cervo place buoys off of charted but submerged rocks as a reaction to a yacht that had an issue with that rock.

There is a fundamental tenet in yacht racing (or any other navigation) that the safe navigation of a vessel is the sole responsibility of the Captain/Skipper/Person in Charge. When did it become the responsibility of event organisers to legislate against this principle?

If these events (specifically the likes of the VOR, Vendee etc) really want to start regulating how a boat should be safely navigated then they need to take a look at IRPCAS - as many parts of these fundamental rules are broken on a daily basis - just in terms of safe speeds and visibility etc. Place speed restrictions on yachts?

One part of me hopes that this will only serve to let us know what happened and assist us in learning from the disasters of others, and then just get on with it.

Saturday, 6 December 2014

VOR 06/12 0640 - It's not over

The fleet has made it's way to the second band of light airs and clouds, and running simulations from their 0640z positions, it's not over until...


The pressure will remain relentless, with eyes glued to the tracking in Expedition of AIS targets.

Positions show a significant loss by ADOR to the fleet in the last 6 hours as she felt the full force of the suction of the clouds.


ADOR does appear to be due to break free very soon...but will it be soon enough.

Two results present themselves, routing is now to finish as the finish area starts to come into range of higher res grib files...

0640z GFS 0.5 deg res

0640z GEM 0.25 deg res

Which ever solution above pans out it is clear the leading 3 have their own tustle, ALVI unsure who to play with, and the chasing duo/trio approx 24hr behind.

Both routes a very similar pattern, a drag race to the corner.





Wind distribution for the leg to the E tip of Oman:

Thursday, 4 December 2014

VOR 04/12 0040z - Is West Best?

At the 0040z report the fleet have lined themselves up and pointing at the mark...the big question now is who will have the best windspeed and angle to the corner.

Note that this run was from the 0040z position, at the 0340 report it appears MAPF has better pressure in the E...

Results at 0040z:

With a 370nm east-west spread, the big question is who will have the best angle and speed to the corner. The leaders are taking the safe option and covering both sides of the course. Deliberately or are they just sailing their own race? My feeling is a little bit of both.

Below shows the wind distribution for the E and W options. It appears the SCA1 side of the course has a greater distribution of TWA's, but on average higher TWS, the MAPF option shows similar (possibly tighter) angles but of a trend down the TWS scale.

Both charts run with an interpolation of the GFS and GEM 0.25 deg resolution models.



Route and results:


0.25 GEM 0040z
0.25 GFS 0040z


GEM
GFS

Current will be playing a factor in the leg but should be reasonably even across the fleet, potentially the W option with a better axis? Shown with the Ensemble run from ADOR position Blue is the GFS 0.25, Red GEM 0.25.


Video is from ADOR position, Ensemble run showing the two different weather models (GEM slightly more wind?). Displayed weather is the GFS 0.25 only.