Interpreting Coastal Forecasts

[FishDiver]

What's that the forecast for? It's not Monterey (I log the Monterey offshore
forecasts, and the Monterey Bay forecast will be smaller).

The wind waves and swells add up, but they have different effects. Wind
waves make for a nasty surface swim or small boat ride, but don't effect
the diving much. Swells affect the surface swim and small boat ride
a bit, but mostly create surge on the bottom and surf for beach entries.

NDBC - NWS Forecast
NWS Forecast
FZUS56 KMTR 162246
CWFMTR

COASTAL WATERS FORECAST
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
246 PM PST SAT JAN 16 2010

POINT ARENA TO POINT PIEDRAS BLANCAS AND OUT 60 NM INCLUDING THE SAN
FRANCISCO BAY AREA AND MONTEREY BAY

 

[Peter_C]

Use this one for Monterey. It is outside the bay which will give you a more realistic idea of the swells.

PZZ560-565-170530-
PIGEON POINT TO POINT PINOS TO 10 NM-
POINT PINOS TO POINT PIEDRAS BLANCAS TO 10 NM-

Surfs up Bro...

TUE
S WINDS 20 TO 30 KT. COMBINED SEAS 18 TO 22 FT. RAIN.

WED
S WINDS 20 TO 30 KT. COMBINED SEAS 20 TO 25 FT. RAIN.

THU
NW WINDS 5 TO 15 KT. COMBINED SEAS 20 TO 22 FT. RAIN.

 

[FishDiver]

Use this one for Monterey. It is outside the bay which will give you a more realistic idea of the swells.

PZZ560-565-170530-
PIGEON POINT TO POINT PINOS TO 10 NM-
POINT PINOS TO POINT PIEDRAS BLANCAS TO 10 NM-

Surfs up Bro...

TUE
S WINDS 20 TO 30 KT. COMBINED SEAS 18 TO 22 FT. RAIN.

WED
S WINDS 20 TO 30 KT. COMBINED SEAS 20 TO 25 FT. RAIN.

THU
NW WINDS 5 TO 15 KT. COMBINED SEAS 20 TO 22 FT. RAIN.

Link please.

 

[Peter_C]

It is the same one you are using just look for the third one up from the bottom which is PZZ560.

For the North Coast look to the buoy 10 miles offshore.

 

[FishDiver]

SAMPLE PROBLEM:

NOAA FORECAST (Using the correct region stated by Chuck and Peter C)
FRI
E WINDS 5 KT...BECOMING S IN THE AFTERNOON. WIND WAVES
2 FT OR LESS. W SWELL 7 TO 9 FT. CHANCE OF RAIN.
Wind will knock down waves a bit-result in W waves of 5-7 feet. Great diving day.

FRI NIGHT
S WINDS 10 KT. WIND WAVES 2 FT OR LESS. W SWELL
11 TO 13 FT. CHANCE OF SHOWERS.

SAT
N WINDS 5 TO 15 KT. WIND WAVES 2 FT OR LESS...BECOMING
3 FT. W SWELL 12 TO 14 FT. SLIGHT CHANCE OF SHOWERS.
Poor morning vis due to waves during previous night. North wind equals fair diving along shore in Monterrey Bay. 12-14 swell equals poor boat or shore diving outside the bay. Lousy day for diving.

SUN
N WINDS 10 KT. WIND WAVES 2 FT OR LESS. W SWELL 10 TO
12 FT.
Similar to Saturday, a bit more moderate. Visibility poor owing to Saturday's turbulence.

How did I do?

 

[Chuck Tribolet]

For Friday: WIND??? WHAT wind? And my experience is that it doesn't
knock the swell down at all, just makes the surface much more confused.
If the swell was going INTO the wind, it might knock it down, but the
forecasts consider that. In fact, the forecasts pretty much have two inputs:
Current swell conditions (there are satellites that measure this via RADAR)
Forecasted wind conditions (Other models predict this)

Independent of what the vis is like, Sat and Sun are over my maximums
AT THIS TIME based on that forecast. Navy WAM looks a bit better, esp.
for Sunday's Corry memorial.

 

[FishDiver]

For Friday: WIND??? WHAT wind? And my experience is that it doesn't
knock the swell down at all, just makes the surface much more confused.
If the swell was going INTO the wind, it might knock it down, but the
forecasts consider that. In fact, the forecasts pretty much have two inputs:
Current swell conditions (there are satellites that measure this via RADAR)
Forecasted wind conditions (Other models predict this)

Independent of what the vis is like, Sat and Sun are over my maximums
AT THIS TIME based on that forecast. Navy WAM looks a bit better, esp.
for Sunday's Corry memorial.

Well, I'm glad I asked!

I assumed the 2 foot wind waves from the east would mitigate the 7-9 foot swell from the west. The forecast is net of all these effects, then?

Did I at least get a B?

 

[Chuck Tribolet]

F. The energy in a wave is proportional to the second or third power of the
height (gotta dig out my copy of Willard Bascom, Waves and Beaches). The energy
in the wind waves is NOTHING compared to the energy in the swells. And
the forecasts take all of that into consideration anyway.

 

[Peter_C]

F.

Harsh Chuck! I give him a C- just for trying

With that said, Chuck has years upon years of watching the wave models and comparing them to actual conditions.

We checked the Bodega buoy one fine day and left home with a boat in tow. The forecast called for around 4-5' swells and less than a 10kt wind. Got out there and the wind was blowing hard. The swells were big enough we struggled to make it out of the harbor. We tried running North for a little bit, but there was so much water coming over the bow we turned and headed home. Checked the buoy again when we got home and it still showed the same conditions. Point being if the swell forecast looks like it could be diveable make the drive and stand at the dive site for a while and determine it for yourself. In our case it was not diveable.

 

[FishDiver]

Harsh Chuck! I give him a C- just for trying

Point being if the swell forecast looks like it could be diveable make the drive and stand at the dive site for a while and determine it for yourself. In our case it was not diveable.

How do the charter boats stay in business???

I have a three hour drive to the beach. I want to refine my forecasting skills to the max.