Showing posts from October, 2019

Florida Gulf Stream: An Exercise in Sources

... Well, that title is going to upset some folks right a way. Many feel that the name of the strong current off the east coast of Florida should be called the Florida Current. However, navigation and marine weather publications that make the claim to that name, very shortly move on to call it the Gulf Stream themselves—just as we will, and just as Benjamin Franklin did when he named the current system, 200 years ago.

We consider here a detail (our speciality!) of this current flow that stems from questions that came up in our online class about Question 16 in our online Weather Course Quiz 3: When sailing from West Palm Beach Florida toward Grand Bahama Island located some 70 nmi to the east, how far offshore would you expect to first run into the Gulf Stream Current?  And we give a Hint that such information is in the Coast Pilot, among other sources, including charts, and weather maps, and that we were not talking about the axis of the current, but rather when would we first start …

Southern Hemisphere Weather Maps by Email

Our main source of NWS weather maps for the Atlantic, Pacific, and Gulf of Mexico and Caribbean is the FTP folder located at

What may not be so well known is this folder also includes weather maps for the Central Pacific that extend all the way to Australia. Below is a sample map followed by the file names for these maps. How to access them is discussed below that.

WIND/WAVE CHARTS - CENTRAL PACIFIC                              NAME

00Z Pacific Wind/Wave Analysis 30S-30N, 110W-130E  PJFB89.TIF
12Z Pacific Wind/Wave Analysis 30S-30N, 110W-130E PJFD89.TIF
    Pacific Wind/Wave Analysis (Most Current) PJFB10.TIF

24HR Pacific Wind/Wave Forecast VT00Z 30S-30N, 110W-130E PWFE82.TIF
24HR Pacific Wind/Wave Forecast VT12Z 30S-30N, 110W-130E PWFE84.TIF
24HR Pacific Wind/Wave Forecast (Most Current)     PWFE11.TIF

48HR Pacific Wind/Wave Forecast VT00Z 30S-30N, 110W-130E PJFI89.TIF
48HR Pacific Wind/Wave Forecast VT12Z 30S-30N, 110W-130EPJFI91.TIF
48HR Pacific Wind/Wave For…

Equatorial Countercurrents

This topic comes up now as we are in contact with Jacob Adoram who is rowing his custom build Emerson non-stop from Neah Bay, WA to Cairns, AU, with the longest unassisted ocean rowing record on the horizon.  He has just passed HI (within smelling distance) after 5 months of rowing and is now headed SW towards Cairns, just over 4,000 miles off.  His next navigational challenge is crossing the equatorial current systems, and in particular the countercurrent that takes him the wrong direction. All small craft must navigate these currents when crossing the equator, but this is particularly of interest in a vessel whose average speed is rather slower than a leisurely walking pace.

But with this challenge comes a unique opportunity to learn something about these currents that could benefit other mariners. He can periodically stop rowing and measure the current set and drift and we can compare that with readily available predictions, namely the RTOFS model and the OSCAR analysis of the aver…

Tracking Jacob Adoram: An Exercise in Wind, Waves, and Currents

Jacob Adoram is rowing his custom vessel Emerson from Neah Bay, WA non-stop to Cairns, AU. He departed July 7, 2018 and now (Jan 26, 2019) is located about 1,100 nmi SW of HI making good about 40 nmi a day, with Cairns about 3,000 nmi to his SW.  He has good navigation and weather resources onboard as well as good satcom connections. His position is being posted online, updated hourly at his Where's Jacob? link at A segment of that display is shown below.

Figure. 1 Display of Emerson's position from his PredictWind tracking display, with a model wind and pressure forecast.
That report is being executed via a PredictWind app (PW) in an iPad connected to an Iridium Go (GO) satcom transceiver with wireless router. The GPS position is being transmitted automatically from the GO every hour to a PW website that is linked to from Jacob's webpage. These positions are updated at 43 min after each hour and labeled with that time, but the actual position shown is from…

Countercurrent Crossing Nav Problem Solutions

In an earlier note we posted a navigation problem asking for fastest way to row across the Pacific countercurrent, from 300 nmi off. The current is 1 kt flowing due east, over a 200 nmi span. The hypothetical rower can go 2.0 kts in any direction. The rhumb line route (RL) to the finish at Cairns, AU is 240T. We assume—not very realistically—that conditions on either side of the current are about the same and that we could indeed achieve a speed made good (SMG) of 2.0 kts in any direction outside of the current.

Please note:  this rowboat exercise is unique, but the problem itself is realistic and standard. Imagine, for example, that we change to sailboat, and consider the wind calm over the current (often in the doldrums) with a motoring speed of 6 kts, and then we put NE and SE trades on either side of the current belt and set sailing speeds to match the vessel.  The same types of current reckoning would still have to be carried out.

The challenge here is to find the best method to …