With Jacob's successful completion of his mission, we are now done with our tracking and discussions.
The KML file functionality should still work, which might be of interest to those who want to make something like that, but there will be no further updates at this end, and the actual track of positions might disappear as well.
At some point we will compile our many ASCAT overlays and when that is done we will post it on our own nav blog.
Congratulations to Jacob and his supporters.
Friday, July 5, 2019
Saturday, June 8, 2019
15z Jun 8—Jacob Arrives in north part of Cairns. Voyage complete!
After a very difficult last 10 miles, Jacob has safely arrived at Trinity Beach, Yorkey's Knob marina according to local newspapers. We do not have any word from him to confirm any details. Readers must buy a subscription to read the articles... no teasers; no samples! Once the newspaper gets the story onto their facebook page there might be a link to read it.
A historic voyage completed, with many records under his belt.
I thought he might have anchored last night, but it seems he did not... just powered on through.
Friday, June 7, 2019
01z Jun 8—Why Jacob's Anchored positions are more uncertain than underway
Update, the next morning: He did not anchor, as speculated here, but indeed went straight through to land in Trinity Beach (Yorkeys Knob Marina), north part of Cairns.
We can see on the Google Earth presentation of Jacob's track that the reported GPS positions are more scattered over a larger range than when he is anchored than when he is underway. You can see this in the Google Earth presentation online. Zoom into the track before he anchored at Flynn Reef. Below is a sketch of the situation.
I apologize for all of these rough sketches in this note. This is a passing thought (and timely) that does not justify, and i hope not require, finer artwork.
The yellow range shows the position reports from an anchored position. They spread over about 4.5 miles range. GPS has an inherent accuracy of about 100m or better. The pink positions are his reports from the same system once underway. In both cases, our presentation of each hourly position report is a sliding average over the past 3 hr.
Here is a plausibility argument of why the position scatter might be larger when anchored.... and indeed an argument that he might be anchored once again (03z Jun 8).
The position accuracies are poor because the GPS antenna is below decks with a limited view of the horizon. With limited view, it sees only a few satellites, and the intersection angles are narrow, which introduces large fix uncertainties.
Here schematically we see LOP1 intersecting with LOP2, and then consider a small error in LOP2 called 2'. We see the resulting error in intersection is large, whereas with a steeper intersection (ie nearer 90ยบ intersection) the same small error in one of them has less effect on the fix. And on top of that, a 2-d GPS fix (ie elevation at sea level is known) actually requires 3 LOPS. The third one is key to how GPS works; it is used to remove the time uncertainty in the signals—the "LOPs" are actually range rings measured by how long it takes the signal to get to the GPS antenna from the satellite.
Here is a schematic of the restricted view of the sky from within the vessel...
The outer circle is the sky; the areas on the sky are what is seen through two port light windows on either side of the vessel—I do not know the real geometry of this on Jacob's boat. When the boat rolls, one side sees higher, the other looks into the water. When the boat yawls, one window looks more forward; the other more aft, and so on.
When anchored the boat does move around at the end of the anchor line, but if the wind is strong, it is likely to be held more or less in line, and if it does sail back and forth some in the wind, it will be a relatively slow change.
It seems the view of the sky will change with time when anchored, but that it will be much slower and less dramatic than when sailing (rowing).
When underway, this theory is that the two portlight views sample much more of the sky during a fix than they do at anchor, which gives the GPS access to more satellites and hence better fixes than when anchored with limited view.
This may or may not be true. There may be other factors at play. I am standing by to hear your thoughts on this. Post a comment if you have another interpretation of any support for this idea.
For now, and for the moment, I will use this argument in a video below that he has anchored again, near Cairns anchorage CA1 or CA4. I say that because his track progressed normally from the last anchorage to this location and then just stopped and scattered.
The alternative is he is fighting against the wind and not making progress, which is effectively like anchoring, when it comes to sampling the sky through limited access.
I have not heard from his since he left Flynn Reef, so i do not know the answer.
Here is a video discussion of the points above and others related to his current position:
We can see on the Google Earth presentation of Jacob's track that the reported GPS positions are more scattered over a larger range than when he is anchored than when he is underway. You can see this in the Google Earth presentation online. Zoom into the track before he anchored at Flynn Reef. Below is a sketch of the situation.
I apologize for all of these rough sketches in this note. This is a passing thought (and timely) that does not justify, and i hope not require, finer artwork.
The yellow range shows the position reports from an anchored position. They spread over about 4.5 miles range. GPS has an inherent accuracy of about 100m or better. The pink positions are his reports from the same system once underway. In both cases, our presentation of each hourly position report is a sliding average over the past 3 hr.
Here is a plausibility argument of why the position scatter might be larger when anchored.... and indeed an argument that he might be anchored once again (03z Jun 8).
The position accuracies are poor because the GPS antenna is below decks with a limited view of the horizon. With limited view, it sees only a few satellites, and the intersection angles are narrow, which introduces large fix uncertainties.
Here is a schematic of the restricted view of the sky from within the vessel...
The outer circle is the sky; the areas on the sky are what is seen through two port light windows on either side of the vessel—I do not know the real geometry of this on Jacob's boat. When the boat rolls, one side sees higher, the other looks into the water. When the boat yawls, one window looks more forward; the other more aft, and so on.
When anchored the boat does move around at the end of the anchor line, but if the wind is strong, it is likely to be held more or less in line, and if it does sail back and forth some in the wind, it will be a relatively slow change.
It seems the view of the sky will change with time when anchored, but that it will be much slower and less dramatic than when sailing (rowing).
When underway, this theory is that the two portlight views sample much more of the sky during a fix than they do at anchor, which gives the GPS access to more satellites and hence better fixes than when anchored with limited view.
This may or may not be true. There may be other factors at play. I am standing by to hear your thoughts on this. Post a comment if you have another interpretation of any support for this idea.
For now, and for the moment, I will use this argument in a video below that he has anchored again, near Cairns anchorage CA1 or CA4. I say that because his track progressed normally from the last anchorage to this location and then just stopped and scattered.
The alternative is he is fighting against the wind and not making progress, which is effectively like anchoring, when it comes to sampling the sky through limited access.
I have not heard from his since he left Flynn Reef, so i do not know the answer.
Here is a video discussion of the points above and others related to his current position:
17z Jun 7—On the Entrance Channel to Cairns
Jacob got started later start than anticipated, but he did leave and indeed got by the two reefs he needed to pass. Now on the entrance range to Cairns, about 9 nmi off.
We shall see how he proceeds in this last short leg. It will be light in about 2 hours.
Thursday, June 6, 2019
00z Jun 7—Jacob underway from Flynn Reef to Mission Bay
Background: Notes here on our Google Earth tracking of Jacob Adoram Index of Google Earth overlays. Download the KLM file.
Just got word from Jacob that he is getting underway shortly. We can watch him on Google earth; download the KML file above and drag to Google Earth.
This is likely the most exciting leg of the entire year-long voyage.... this last 20 nmi getting across the Great Barrier Reef!
* * * NOTE: our GE positions are 3-hr averages, so we will not get a good track until 3 hr after he leaves. At 00z he said "in a few hours," maybe 9z or so we might see the track.
20z Jun 6—Cairns in Sight; again waiting on the wind
Background: Notes here on our Google Earth tracking of Jacob Adoram Index of Google Earth overlays. Download the KLM file.
New KML online now with new charts and routes
Safely anchored off of Flynn Reef, Jacob is still waiting for lighter wind.
We discuss in the video below the situation, including charting anomalies, and glimmers of faint hope in the forecast for tomorrow... which is just about 10 hr from now.
See https://www.jacobadoram.com/blog for a nice long review from Jacob on present conditions.
We are watching the wind with several posts in our blog:
One on the things we think we are learning is the Oceanic version of the National Blend of Models might provide best extended forecast. We have one more test of this underway that is Jacob oriented, but then we can do the same thing across the globe by watching conditions at several buoys that have live data to compare with. We are homing in on the best ways to present this. The best source of data is clear, namely LuckGrib, because it is the only source and viewer for the probabilistic data from NBM and the statistical data from the GFS Ensemble runs, GEFS.
Here is the link for the Metop-A tracking site that we are using to watch for daylight times at Jacob's location: http://www.lizard-tail.com/isana/tle/plot/?terminator=true&catalog_number=29499&color=white
Another nice way to do both is the free PC app Orbitron, but our forthcoming video on how to use it will be helpful.
Monday, June 3, 2019
00z Jun 4—Anchored and moored waiting for less wind
Background: Notes here on our Google Earth tracking of Jacob Adoram Index of Google Earth overlays. Download the KLM file.
New KML online now with new charts and routes
We got word yesterday that the wind was relentless at 170 to 180T at 30 kts gusting to 35. This was simply unmanageable so he looked for first opportunity to anchor and wait it out. He found a place just on the west side of Flynn Reef, and we made a new chart insert to show this on the google earth. Please update the KML to see it.
As luck would have it, after his anchor caught (a 16# Danforth, with 200 ft of line) and he played out the line, he noticed a mooring buoy right there so he is tied to it and his anchor...which is good news as the winds are still strong.
Below is a pic Jacob just sent.
Jun 4 03z. Notice the prominent streaks on the waves. That is a typical telltale sign of wind approaching 30 kts.
It's hard to see in this pic, but he says he can see the green water ahead where the reef is located. ("Green water" and green reef on the chart is a coincidence of course. The latter simply means that at zero tide height the reef is exposed... depending on the waves.)
We also see here his two radar reflectors; the antenna on the top is maybe his AIS transceiver to monitor traffic and be monitored. The white instrument looks like a sonic anemometer. The boat is moored at the bow.
We also see here his two radar reflectors; the antenna on the top is maybe his AIS transceiver to monitor traffic and be monitored. The white instrument looks like a sonic anemometer. The boat is moored at the bow.
I thought his discovery of a mooring buoy was really unusual, but these are what the dive boats hang onto while diving the reef. He is just off the reef to the west, both anchored and moored.
You will also notice on the Google Earth display a huge spread in the GPS fixes. This is not normal! This comes about because his GPS receiver antenna figuring the tracking positions is on Iridium Go box and that is below decks, in fact even worse, under a solar panel. The GPS antenna can barely see the horizon, which limits the view to only a few intermittent satellites, maybe even in the same direction, and hence to poor fixes. In this case really poor fixes. If we had this GPS in hand, it would be warning us of this; the tracker code does not do that.
Users of the popular Iridium Go should be aware that the GPS antenna used for the tracking signals is in the stubby antenna connected to the box. Even if you have a very nice external antenna that enhances the satellite connections this does not improve the GPS. There is no GPS receiver in that external antenna.
Below is our system, which is a sliding average over the past 3 hrs of PredictWind positions.
True position is the red and yellow dot. The red line is 4.5 nmi long, which shows a huge range in GPS positions, all artificial. A GPS with good antenna would be well within a 100 meters or so. Dotted circles are the averages of past 3h reported positions from PredictWind tracker, shown below
Blue dot is the true position. In this static collection of data points, it is not clear if the Starpath averaging is improving the display, but underway it is definitely better which can be seen by comparing our GE display with the PW display.
We will watch the weather to see when he might get underway again. ASCAT passes show strong will still, and models do not show relief this week.
See how we evaluate the forecasts at this note on crucial weather routing. Our conclusion is that the FV3 GFS model did the best for the longer term (~96h) forecasts. The Oceanic National Blend of Models was the best for short term (day or two).
We can see the tides in that region from within OpenCPN, where we have the AU charts installed. The tide data come with OpenCPN. We see below that the tide in this region has a range at the moment of about 2m or about 6.5 ft. That seems to imply that he might see the reef dry briefly if the waves don't interfere.
Tide stations near Flynn Reef, viewed in OpenCPN.
See how we evaluate the forecasts at this note on crucial weather routing. Our conclusion is that the FV3 GFS model did the best for the longer term (~96h) forecasts. The Oceanic National Blend of Models was the best for short term (day or two).
We can see the tides in that region from within OpenCPN, where we have the AU charts installed. The tide data come with OpenCPN. We see below that the tide in this region has a range at the moment of about 2m or about 6.5 ft. That seems to imply that he might see the reef dry briefly if the waves don't interfere.
Tide stations near Flynn Reef, viewed in OpenCPN.
Below is a video discussion of these topics...
You can see the live Cairns report at: http://www.bom.gov.au/qld/forecasts/cairns-coast.shtml. Not looking good at the moment.
Weather Situation
A high pressure system [1039 hPa], moving slowly eastwards over the Great Australian Bight, will extend a firm ridge over northern Queensland waters for the next few days with fresh to strong southeasterly winds.
Forecast for Tuesday until midnight
Strong Wind Warning for Tuesday for Cairns Coast
- Winds
- South to southeasterly 20 to 25 knots, reaching up to 30 knots in the late morning and afternoon.
- Seas
- 1 to 1.5 metres, increasing to 2 to 3 metres outside the reef.
- Swell
- Easterly 1 to 1.5 metres outside the reef, decreasing to around 1 metre later in the evening.
- Weather
- Partly cloudy.
Wednesday 5 June
Strong Wind Warning for Wednesday for Cairns Coast
- Winds
- Southeasterly 20 to 25 knots, reaching up to 30 knots inshore north of Cape Grafton in the afternoon.
- Seas
- 1 to 1.5 metres, increasing to 1.5 to 2.5 metres outside the reef.
- Swell
- Easterly 1 to 1.5 metres outside the reef, tending southeasterly 1 to 1.5 metres during the morning.
- Weather
- Partly cloudy.
Thursday 6 June
- Winds
- Southeasterly 20 to 25 knots.
- Seas
- 1 to 1.5 metres, increasing to 1.5 to 2.5 metres outside the reef.
- Swell
- East to southeasterly 1 to 1.5 metres outside the reef.
- Weather
- Cloudy. 70% chance of showers.
Sunday, June 2, 2019
04z Jun 3—Anchored off of Flynn Reef
Background: Notes here on our Google Earth tracking of Jacob Adoram Index of Google Earth overlays. Download the KLM file.
New KML online now with new charts and routes
Jacob is now anchored off of Flynn Reef. Southerly winds of 30 kts gusting to 35 were too much to cover come. He missed first attempt to grab an anchorage, but caught the next one and is anchored now waiting for new wind... looks like he may not see that till Thursday.
You can get Cairns marine weather at
Here are a few short video notes and links.
Jun 2—Jacob now transiting the Great Barrier Reef
Background: Notes here on our Google Earth tracking of Jacob Adoram Index of Google Earth overlays. Download the KLM file.
New KML on line now with new charts and routes June 2 1524 PDT
For those who might be following this blog post, now is the time to turn on Google earth for hourly updates.
Jacob has turned to enter the region of the reefs so this is the last crucial step of the voyage. Positions online are updated hourly, but they are the average of the reported positions over the past 3 hours... we have to do that because the raw GPS data from the vessel is uncertain for reasons we explained earlier.
Also keep in mind it is pitch dark (no moon) where he is at the moment, so he is "flying by instruments," which he is well accustomed to as a former combat pilot.
PS... he did not choose to enter in the dark! In these strong winds without a sea anchor or drogue, he cannot slow down. He is there, when he is there.
This is 12:11 PM Seattle time, which is 0511 in AU, which we see here is still dark. It is winter there. The meridian lines shown on this map are 2 hr a[art, so he has about 2 hr more of darkness at this time.
This screen cap is from the free PC program called orbitron, which i am running on a Mac using WINE. I will post a couple articles about this program in our Starpath nav blog. We use it to predict passing times of Metop-A and Coriolis, the scatterometer satellites.... the daylight terminator is a bonus to us, but crucial to those who want to visually see the satellites cross the sky.
A video note on this announcement:
Saturday, June 1, 2019
Jun 1—Great progress; ETA in hand
Background: Notes here on our Google Earth tracking of Jacob Adoram
Index of Google Earth overlays. Download the KLM file.
We are updating frequently now, so best to download the KML file and update your Google Earth.
Jacob is making good about 2.3 kts, on course to Flora Pass, which at 18z on Sat Jun 1 is just 62 nmi off. He is getting some help from the currents, and wind is strong and right on the stern. We see this in the ASCAT images, but strangely the WindSAT data do not agree. This we will look into elsewhere. (We also have to consider that Jacob has indeed seen periods of wind at 10 kts from 070, so maybe there is some chance the WindSat captured this unusual transient wind.)
We note that the local coastal forecast from Cairns is still 20 to 25 kts, but we have at least one example where this was an overestimate. For Jacob and his boat, 20 kts is difficult to steer in, but 25 kts is notably more difficult, with much limited range of headings.
Below is a video discussion of these points and others...
Jacob is making good about 2.3 kts, on course to Flora Pass, which at 18z on Sat Jun 1 is just 62 nmi off. He is getting some help from the currents, and wind is strong and right on the stern. We see this in the ASCAT images, but strangely the WindSAT data do not agree. This we will look into elsewhere. (We also have to consider that Jacob has indeed seen periods of wind at 10 kts from 070, so maybe there is some chance the WindSat captured this unusual transient wind.)
We note that the local coastal forecast from Cairns is still 20 to 25 kts, but we have at least one example where this was an overestimate. For Jacob and his boat, 20 kts is difficult to steer in, but 25 kts is notably more difficult, with much limited range of headings.
Below is a video discussion of these points and others...
Thursday, May 30, 2019
May 31—Final approach; A lot going on
Background: Notes here on our Google Earth tracking of Jacob Adoram
Index of Google Earth overlays. Download the KLM file.
We are updating frequently now, so best to download the KML file and update your Google Earth.
Jacob had been holding back waiting for better forecast before completing the last leg of his voyage, up to Flora Pass (160 nmi), though the Great Barrier Reef and on into Cairns. A total run of about 185 nmi.
That better forecast did not show up, so he has taken off now, with hopes of getting there before the worst of it. The video below goes over the route and mentions our study of the wind forecasts at
http://davidburchnavigation.blogspot.com/2019/05/tools-for-crucial-weather-routing.html
It is an interesting ongoing study of the models, hoping to learn which one was most successful in this difficult to forecast atmosphere.
Not mentioned in the video is our concurrent study of the scatterometer wind data from ASCAT and WindSAT. We look for cases where they are close passes and see if they read the same winds. This is long overdue. If the WindSat data are reliable, this is another large set of real wind measurements sailors can use.
See http://davidburchnavigation.blogspot.com/2019/05/compare-ascat-and-windsat-scatterometer.html
We have half a dozen new samples that we will add on Friday May 31.
He is close enough now to look ahead to actual wx forecasts at Cairns, sort of equivalent to our VHF weather. Here is the latest report:
Weather SituationA high [1035 hPa] over the Great Australian Bight extend a strengthening ridge along far northern Queensland waters with fresh to strong southeasterly winds developing.Forecast for Friday until midnightStrong Wind Warning for Friday for Cairns CoastWindsSoutheasterly 20 to 25 knots, reaching up to 30 knots south of Cairns in the late afternoon and evening. Lighter southerly winds inshore south of Innisfail in the late morning.Seas1 to 1.5 metres, increasing to 1.5 to 2.5 metres south of Innisfail by early evening.SwellEast to northeasterly around 1 metre outside the reef.WeatherCloudy. 80% chance of showers.Saturday 1 JuneStrong Wind Warning for Saturday for Cairns CoastWindsSouth to southeasterly 20 to 25 knots, increasing to 25 to 30 knots inshore north of Innisfail.Seas1 to 1.5 metres, increasing to 1.5 to 2.5 metres outside the reef.SwellEasterly 1 to 1.5 metres outside the reef.WeatherCloudy. 95% chance of showers.Sunday 2 JuneWindsSouth to southeasterly 20 to 25 knots, reaching up to 30 knots at times north of Cairns.Seas1 to 1.5 metres, increasing to 1.5 to 2.5 metres outside the reef.SwellEasterly 1 to 2 metres outside the reef, decreasing to 1 to 1.5 metres during the morning.WeatherCloudy. 70% chance of showers.
So we see there are indeed strong winds forecasted for the moment. He would be there now on about June 3.
You can read the latest report online at http://www.bom.gov.au/qld/forecasts/cairns-coast.shtml
Wednesday, May 29, 2019
May 29—Waiting out the forecasts.
Background: Notes here on our Google Earth tracking of Jacob Adoram
We are updating frequently now, so best to download the KML file and update your Google Earth.
Jacob is poised and ready to finish this epic voyage, but on hold due to the longer term forecasts. His next leg is a 160 nmi run to the NW to the entrance of Flora Pass, which takes him though the Great Barrier Reef, and then on to Cairns, about 40 nmi from there.
The problem now is that last turn into Flora Pass and the passage through the Reef. The strong SE winds are excellent for running up to the Pass, but not good at all for turning to south of west to transit the Reef area. His large boat cannot be controlled with strong winds on or near the beam.
Details of the passage through the reef can be seen in the Google Earth overlay.
He has been watching this forecast now for several days, and it has not been very encouraging. First the winds are strong at the turning time (up to 28 kts, often to 20+) and second, the models do not agree on the forecasts. We have an article in another blog that compares these models along with other models that even provide probabilities of winds.
In any event, it looks like the strong wind forecast is not going away anytime soon. It could be well into next week. Furthermore, Jacob knows by direct hard first hand experience that these trades can crank up to 15+ and stay that way for weeks. So this is a time for patience.
Below are weather maps from BOM that show the source of these strong trades.
We see that the isobars where we care about are affected by the High over AU as well as fronts moving around to the SE of AU.
I am not sure if models used by BOM are independent of the ones we follow in the link above, but here is what they forecast for this period... we are using 12z on Fri as a benchmark. These are taken directly from our Google Earth overlay on Jacob's track. The data are from BOM.
Here are now the maps from Thursday May 30:
We see the main problem by looking at the 1016, 1020, and 1024 isobar as they approach Queensland from offshore. They get closer together and that is what makes this strong wind near the coast. There is some indication here that this is weakening on June 3, but we have to wait and see.
Sunday, May 26, 2019
May 26—Back on Course, 280 nmi to go, another challenge on the horizon.
Background: Notes here on our Google Earth tracking of Jacob Adoram
We are updating frequently now, so best to download the KML file and update your Google Earth.
With such great progress under the belt now, it is easy to forget that any ocean voyage is not complete until the boat is tied up at the dock. All looks great for the moment, but there is a forecast for strong winds right at the finish line, about 8 or 9 days out now, which i am sure Jacob is thinking about already. The forecast might not pan out; this is a change 5 days out, so that would not be a surprise, but this is a classic case of spotting something early, and then watching it at every forecast until decision time arrives.
On present schedule he would turn north on Wed 30th UTC, then the wind starts to build on Thursday or Friday. Here is the meteogram from LuckGrib.
We will watch this forecast every 6 hr going forward. We are using the FV3 GFS model, which will become the official US GFS model on June 12. After that, there will not be two models, just GFS.
We note in the video below that the ASCAT data is gone missing. Something is wrong. We can see the data at KNMI, but not at the OSWT site that we rely on.
Here is a video discussion with nautical charts...
Saturday, May 25, 2019
May 25—Good progress continues.
Background: Notes here on our Google Earth tracking of Jacob Adoram
We are updating frequently now, so best to download the KML file and update your Google Earth.
Good progress continues. We added the Navy WindSat scatterometer (on satellite Coriolis) to the ASCAT scatterometer (on the satellite Metop-A). It is not often we can compare the data for the same time exactly, but we will try to do that when possible.
Here is a preliminary comparison.
and then the ASCAT data 14 hr later...
We have also added new range rings at 100 nmi, and shut off in default mode the 400-mile rings. He is now well under 350 nmi to go, which could seem like a lot until we remember he has rowed something approaching 9,000 miles!
Check back later for a video discussion and demo to date... discusses charts and lights, as well as relative climate... ie Cairns is "south of Jamaica." [This has been postponed till tomorrow's post.]
We will also be adding shortly a note and video on how to track the scatterometer satellites to predict future passes.
Thursday, May 23, 2019
May 23—Congratulations Jacob! Major Accomplishment.
Background: Notes here on our Google Earth tracking of Jacob Adoram
Please download a new copy of the KML file. We have added several features, including WindSAT scatterometer data and new charts,
Jacob has gotten around the Lihou Reef which was a tremendous amount of work for him, fighting the 25 + kt SE trades. This has lightened up as forecasted, thank goodness, and now he is doing well on course to meet the next one: Tregrosse Reefs, which are about 60 miles off, which is a bout a day and a half.
Wind forecast is favorable for this, but it is still a lot of work in rowing this big boat of his. A LuckGrib meteogram assuming 1.6 kts on the indicated course is below.
We see the wind staying below 15 kts which is manageable. You can view the climatic winds at the Google Earth posting, which we home maintain or go lighter for the duration of the voyage.
We will post shortly a new tool for noting if Jacob is in daylight or darkness. Plus we have to make a post on a fantastic new source of nautical charts.
Here is a short audio discussion.
Here is a WindSat image from our GE overlays that was valid at 21z on May 23. This was not processed yet at the time this note was originally posted. It could be the WindSat data takes longer to process than the ASCAT. I need to check that. We do get good wind data this way in most cases. I think if the WindSat and ASCAT disagreed in any circumstance, most meteorologists would go with the ASCAT.
Tuesday, May 21, 2019
May 21 — Challenges ahead
Background: Notes here on our Google Earth tracking of Jacob Adoram
The main challenge at the moment is getting south of LiHou Reef, or deciding very soon to turn and follow the wind over the top. Jacob is fighting hard at the moment to keep the track south of west. Recall his boat Emerson is big (28ft x 5 ft), and in strong wind (he has sustained 20 kts +, often a steady 25 kts, sometimes approaching 30, from the SE) it is very difficult to control the boat. He is in huge trade wind seas as well to deal with.
The situation is discussed in the video below. This morning there are signs he could turn south a bit so that is very good. The meteogram of forecasts is below, showing there is some slight improvements on Thursday and Friday, but Wed, tomorrow, still is a big challenge. The winds pick up to solid 25, which we also see in the ASCAT, and even veer a bit more to the SE. So the key now is getting past Wed.
We have a new KML file with chart segments loaded. Also found this very nice link to Sat images over AU. http://satview.bom.gov.au/
AU tides for this region are also online. There is a station at the top of the reef. Tide range is about 6.5 feet in this area. Tides affect not just the depth, but also the currents running between the cuts or passes in the reefs.
Progress now is judged not day by day, but hour by hour. The KML file is updated hourly.
Update 1640z tuesday last 4 hours very good course to the south.
Below is the GFS ensemble model, which outputs a standard deviation (SD). we expect 67% of all winds within 1 SD, but deviation could be higher or lower than mean. we see see SD about 1 for Tuesday meaning forecasts 18±1 kt, then 1.5 on wed and thurs is more uncertain with ± 2kts, then strangely Friday is back to ± 1.5. Generally the SD just gets bigger with time. Average pressures gradually falling with back to about 1015± 1 on Thursday Friday.
I think this is all pretty normal for a normally good forecast. When the forecast is bad, the SDs can get very large. For TC Ann sometimes the SDs equaled the wind speeds!
this plot is from present position on a heading of 266 T at 1.6 kts. Possible routes do not affect this too much, but as all is better to the south, the winds are also a bit lighter to the south as well.
This is from LuckGrib, which has a nice option to display the SDs.
Thursday, May 9, 2019
May 12 -— A Brush with a Tropical Storm
Background: Notes here on our Google Earth tracking of Jacob Adoram
We see favorable currents on the horizon, which he might be able to reach.
An ASCAT pass shows real wind speeds. Purple is 50+. This storm is moving quickly to the west, toward about 290 T. It had come down from the north, then stopped, then turned and went West. It was first forecasted to cross the rhumbline and keep going to the southeast. Then it was forecasted to dissipate at the rhumbline, then a day or so ago the track got better... but the wind speed forecasts did not.
Compare that to the GFS forecasts below of 30 kts. This and other issues are discussed in the video link below.
Tuesday, May 7, 2019
May 8 — Major Milestones Achieved; Still Challenges Ahead
Background: Notes here on our Google Earth tracking of Jacob Adoram
I started this on May 2, when it was true that: After covering 5,400 nmi made good across the globe from Neah Bay to his present position, accomplished by actually rowing a staggering 8,500 nmi (over one third of the earth's circumference) along the twisted course dictated by wind, waves, and current.
Jacob is now well past the 1,000 miles to go mark. This morning he is 961 miles from Cairns and making good progress. Conditions look good for the next 4 days, but there is a storm on the horizon that he will have to negotiate.
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It is now May 8, and a lot has happened. First he is well into the past 1,000 mile mark and getting closer to approaching another milestone of 800 nmi off. This leaves just one more of our 400 nmi range rings to cross.
He has also set the milestone in that there is just one more island group (Coral Sea Islands) to get past before Cairns. He is essentially past the dangerous Indispensable Reefs, with open water for about 600 nmi till the Coral Islands Group. We may need to do some digging to get charts of these reefs.
The real challenge at hand has been a loose cannon storm that has been since May 3rd a classic case of impossible to forecast. He will start to feel the winds of this tomorrow, one way or the other, but it could get deeper. I illustrate present and past forecasts of this in the video below, but need to make a better demo of just how wrong the forecasts have been.
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