Evaluating wind models in 2025 Sydney-Hobart Race

 We have been following the TransPac52 fleet in the 2025 Sydney Hobart Race as a way to learn about evaluation of  currents and winds and routing for practice in our online marine weather and electronic charting courses. 

At about one and half days into the Race as boats approached Bass Strait, they were beating into strong southerlies (25 to 30 kts) flowing against some 2 kts of current, which created tremendously steep and violent seas.  Three of the five TP52 fleet have retired from the race, with some 17 others at this point. 

Of the two left, they are on different tracks, one that looks more favorable at this stage.  Here we will look at the wind models, comparing 1 GFS, 2, ECMWF, and 3 ICON.  Earlier in the race it appeared that ICON was more favored, but it also had winds too strong inland at the start.  We shot out of the Bay way to fast and once around the corner and into more dependable ocean winds, we hove-to to wait for the TP 52 fleet, then started the routing again, using ICON and enhanced OSCAR currents.

Below we see the situation with currents approaching the Strait, which we discussed earlier.

These are the OSCAR currents that match the AU studies. C would be logical place to be with 2+ kts of favorable current, but not when you are beating to the south against strong wind. Seas too big. Normally we would head to the beach, as Highly Sprung #2 has done to get out of the current—but current is likely flowing north there in this case. It looks like Frantic has found a nice wind median with light favorable current... assuming of course that this model, which matches the AU study (cited in the video above), is correct. 

The boat tracks shown are from the DCC option in qtVlm (menu Boat/Race Data DCC) that fetches and plots the boats from any major yacht race with standard tracking, such as YB. (I will add a note on that function after the race.)

As for wind, it looks like at this time in the race, at this location, the three models we have been following are in near agreement.  We look at the three points A, B, and C above, which we can compare to a corresponding ASCAT pass.

Viewed in qtVlm, Black is GFS, red is ECMWF, and Blue is ICON.  The above view is 1200 on 12/27/2025, and there is an ASCAT pass at 11:56 shown below (METOP-B, Ascending).  

Here we see the corresponding 25 at C, 15 at B, and 10 at A. In short, the three models agree with each other and with the ASCAT, so we can route with either of them... BUT, we are likely best to use GFS as it has the wave data in it, and then we can turn on some routing filters that account for sea state. More on this shortly..

More specially, here are meteograms at A, B, and C, which is from 1600 (4hr later), but with the same relative values and conclusions. 

Look at the winds on the far left for that time, and then note that the three models agree in speed and direction, numbered as above, now and for the next two days. Solid lines are wind speed; dots are wind direction.

The Three Sets of Nautical Chart Symbols We Need to Know

In 2025, all traditional paper charts were permanently discontinued, after which the only official NOAA nautical charts are the electronic navigational charts (ENC). The International Hydrographic Organization (IHO) set the standards for ENC, including the database of all possible chart symbols, which appears in the IHO document S-52. 

This standard includes the (questionable) option to offer two choices for many of the ATON symbols. One set they call Simplified Symbols and the other they call Paper Chart Symbols. 

"Simplified" symbols is a reasonable name for the first set, shown below, as they are indeed that, but "paper chart" symbols, also shown below, may not be so familiar to US mariners as they do not match common symbols that were used on NOAA paper charts. We have to just interpret the IHO paper chart symbol set as being more like the paper chart symbols we were used to than the simplified set is, which are not at all like paper chart symbols.

The IHO name of "paper chart symbols" makes perfect sense to mariners outside the US, because these are actually very similar to the International paper chart symbols, defined in IHO S-32. In the NOAA Chart No. 1 booklet, the column of symbols on the left headed INT are the international set. NOAA does use that set by default for many symbols, but the ubiquitous symbols for buoys, beacons, and lights are replaced on NOAA charts by their own set of symbols in the column headed NOAA.

Samples of IHO S-52 Simplified chart symbols. From what IHO calls the ECDIS Chart No. 1,  a custom set of ENC, also available in print in S-52

Samples of IHO S-52 Paper Chart chart symbols from ECDIS Chart No. 1.

In principle that would be the end of the discussion with regard to NOAA (US) nautical chart symbols, because we no longer have any traditional paper charts. But with the demise of the traditional paper charts, NOAA created an interesting new concept in paper charts called NOAA Custom Charts (NCC). These are charts we create ourselves with an online NOAA app, where we choose any region of US waters we want a chart for—it does not have to match past or present official chart boundaries—and we choose a scale and paper size we want, and then we create a high-res PDF nautical chart based on the latest ENC data for that area, which are updated daily. It is then our job to get these printed at the size we ask for, on the quality of paper we want, or send the file to one of a handful of companies already set up to print them. See notes on NCC at stapath.com/NCC.

We can even store a file on our computer that defines the choices we made for one or more specific charts, then if we want an update, we just use that file and do not need to redesign the chart—which can take some time to figure out the optimum set of parameters.

The NCC is a very promising chart concept, now a couple years old, but still developing with clear needs for improvement in several areas. One choice on the NCC that NOAA made (which could be questioned) is to use the historic NOAA paper chart symbols on these charts, even though the charts themselves are based on the ENC data, instead of using the official ENC "paper chart" symbols. The purpose of that choice was to make these new NCC appear more familiar to US mariners. 

Since many US mariners will indeed make NCC, if not for primary use, at lease as back up to the ENC on a computer screen, the NOAA decision to use that symbol set has the effect of extending the life of these traditional NOAA paper chart symbols into the future, where, in principle, we would have had just two symbol types: the IHO simplified symbols and the IHO "paper chart" symbols. In short, we now need to know three sets instead of just two.

I believe that eventually NOAA will change to using the ENC paper chart symbols on the NCC, and then the transition away from NOAA paper charts will be truly complete. I think they are just waiting for a generation of traditional paper chart users to become less active, while the new generation of electronic chart users becomes more active who will prefer their supplemental paper charts match their official working ENC.

Selection from NOAA Chart No. 1 booklet. The INT column is similar to ENC paper chart symbols. The NOAA column is what are used on NCC charts. For this category, the NOAA symbols and the NGA (Navy) symbols are the same. For other symbols these can differ.