Hi, The April to June 2022 "packo predictions" for Port Phillip Heads are now available from the updated links at the top of the original post. Next expected 3 monthly update (July --> September 2022) will be posted around the 22nd of June 2022. cheers & stay safe both above and below the water packo Statistics: Posted by packo — Tue, 22 Mar 2022 1:53 am ..read more

Hi, The January to March 2022 "packo predictions" for Port Phillip Heads are now available from the updated links at the top of the original post. Next expected 3 monthly update (April --> June 2022) will be posted around the 22nd of March 2022. I have noted that sometimes that the image hosting site I used can be a little slow to download and sometimes the pictures in my post appear late and sometimes it "times out" with no image load occurring. It is possibly above my pay grade to fix, other than moving to another provider. This would involve a whole lot of work I'm not keen to do. I'll ..read more

Hi, The October to December 2021 "packo predictions" for Port Phillip Heads are now available from the updated links at the top of the original post. Next expected 3 monthly update (Jan --> March 2022) will be around the 22nd of December 2021. Gee the Covid-19 virus is still smashing the world! There has been a very large increase in views of this thread lately, probably by more non-ding folk. So to save a bit on everybodys data allowance I am dropping the display of the tables at the bottom of thread. If you are interested in the tables, please download them via the links at the top of t ..read more

****** Ex HMAS Bayonent and Gulf of Carpentaria GPS "Mystery Marks". ****** 5km lock-down (again) in July! Freezing wind rattling the windows and rain pattering on the roof. What on earth can scuba divers do in these circumstances? Well browsing the Scuba Doctor's dive site webpages is one way to feel "wet" again while staying perfectly warm and dry. I've directed my attention to a few alternative GPS "Mystery Marks" that Lloyd sometimes lists alongside the "Accepted Mark" for some dive sites. He has asked for help from anyone who may have visited and "sounded out" those "Mystery Marks" site ..read more

Hi, The July to September 2021 "packo predictions" for Port Phillip Heads are now available from the updated links at the top of the original post. Next expected 3 monthly update (October --> December 2021) will be around the 22nd of September 2021. Gee the Covid-19 virus is still smashing the world! Hope all those nasty variants can be prevented from taking off in Oz. I got Jab #2 yesterday - wahoo! (here's hoping a blood clot doesn't take me out.) The small scale versions of the monthly predictions appear below just to help ensure they might be caught up in google's (and others) image ..read more

***** Uphill Tidal Flow Through Port Philip Heads ***** No kidding at all! It does happen - for about the last 40 to 80 minutes before slack water. This "last run" of the tidal flow is going uphill, and against a growing uphill slope! Before the words "no-way" escape your lips, please take a long pause. That knee-jerk response would put you in good company with numerous recreational folk, and even many professionals. However the physics, the measurements, the data, the theory, and the numbers all line up to make this one true. It turns out the old adage "water only flows downhill" is not ac ..read more

***** The Bass Strait/Port Phillip Bay "Equal Levels" Moment ***** The equal levels moment at Port Phillip Heads occurs roughly every 6 hrs when the "outside" ocean water level matches the "inside" water level in the vast "main body" of the Bay. The "main body" region begins roughly 15 km inside the entrance. It is a whopping 1,700 square kilometres or so in area. It is the tidal breathing of the vast "main body" surface area with its fairly well synchronised tides that produces such high current speeds at the entrance. Between the entrance and the large "main body" area there is a wedge sha ..read more

***** Forward and Reverse Slopes in the Sea Surface Near Port Phillip Heads ***** Over each cycle of tidal flow, the level differences between Bass Strait tides and the delayed (and smaller) tides in the large "main body" of the Bay create both long duration "downhill slopes", and shorter duration "uphill slopes" in the sea surface across the connection between these two large water bodies. A surface slope is called "forward" if the height decreases in the direction of the tidal current, and "reverse" if the height increases in the direction of the current. The diagram below shows the predic ..read more

****** The "Slack Water Period" ****** One unfortunate consequence of the official "Little White Lie" is the belief that "slack water" has an extended period of no water movement. Scuba divers know this is misleading and with careful observation the current reversal can be seen to occur within just 1 or 2 minutes. As well, the incorrect notion of no or very small forces in play, leads to the view that as the water slows down, the "slowing rate" gets less and less up to the actual slack water moment. In fact in the 30 minutes leading up to slack water the slowing rate grows significantly beca ..read more

***** Water Momentum in Port Phillip Bay's Tidal Streams ***** Like everything else with mass, moving water has momentum. In Port Phillip Bay, circumstances have conspired to make the effect of the momentum of the tidal streams quite significant. Unfortunately the changes of tidal stream behaviour due to water momentum and inertia effects seem to have eluded a large number of government and non-government players who give some incorrect advice about how slack water occurs at Port Phillip Heads. (This area is generally known to Victorians as simply "The Heads" or "The Rip".) The discussion be ..read more