NWS Forecasts.

[Walleye Express]

A board member on my site wrote a letter to the NWS concerning our Wind/Wave forecasts for Saginaw Bay. I was surprised he got any answer back and thought you might find he short answer as interesting and thought provoking as I did.

Jim Hert wrote to Wayne Weeks National Weather Service.

Hi Wayne,

I just wanted to comment on the Near Shore Marine Forecast I hear for the Outer/Inner Saginaw Bay.

I have noticed that the wave forecast seems to only be dependent on the wind knots per mile.

For example with wind 5 to 10 knots the waves forecast are almost always the same, say 1-2 feet.

Obviously though the wind direction has a major impact on the size of the waves. If the wind is out of the SW to the NW the waves could be 1 foot or less with wind speed of 5 to 10 knots. If the wind is out of the NE to the E, coming all the way across Lake Huron, the waves could be 3 to 5 feet! A big difference. We have witnessed this many times. We drive from Hale MI to Au Gres and if the forecast is for 1 foot or less and we find 5 footers when we get there, it is a bit of an inconvience. Now I understand that this is Mother Nature and no forecast is always going to be perfect, but I think the system could use some upgrades and improvements. I'm not the only one with this opinion, most all of the fishermen I know are complaining about how these forecast are not accurate nor reliable and they are constantly looking for other sources of

information.

Thanks,

Jim Hert

Grand Ledge, MI

Dear Mr. Hert...

Thanks for your comments on wave height forecasts for Saginaw Bay. That area has been a frequent trouble spot for us... and we continue to make tweaks to our wave models and product formatters to account for higher waves in those conditions. We made an additional adjustment today, so we'll see if that helps. The new model accounts for some fetch (wind vectors/water transfer) across Lake Huron quite well, but doesn't handle as well the predominant circulation out of the Bay that results in more wave steepness with an east or northeast wind. At some point, we hope to actually have real-time wave measurements on the Bay to help us calibrate the wind/wave relationship there (depends on funding and priorities, as usual). Until then, we would appreciate additional feedback you might be able to give us as we move into the fall season. When you report to us, keep in mind that we are calibrating for "significant waves" (average of the highest 1/3 of the wave spectra) vs. maximum waves.

Thanks again for your feedback and assistance.

Personal observation.

I personally found the word "Fetch" as they used it interesting. I always considered the wind vectors manufactured by the Bays dynamics as having an effect on the forecasts. But never considered the "PUSH" that the outgoing water must have and create on the Bays waves when the wind is pushing NE and straight up the middle of the bay. This may explain why our waves are so close together during high wind events. The smaller ones between the bigger ones must be created by the element and wave echo that is fetch.

[EdB]

Interesting info, thanks for sharing.