| "...Seas 3-5'..." | | | | good reason.) According to the NOAA website, wave |
| How does this statement make you feel? Safe? | | | | height is expressed in terms of what is the average |
| Secure? Just another "calm, nothing can go wrong" | | | | height of the highest 1/3 of all waves in that region. |
| day on the ocean? It SHOULDN'T!! Let's look at just | | | | Here's an example they give for a significant wave |
| exactly what it means: | | | | height of 10 feet: |
| Three to five feet. For most of us that about from our | | | | 1 in 10 waves will be larger than 11 ft |
| waist to our shoulders. No big deal, right? Typically, no. | | | | 1 in 100 waves will be larger than 16 ft |
| ASSUMING that the waves absolutely do not get any | | | | 1 in 1000 waves will larger than 19 ft |
| bigger. We all know what assuming does however, | | | | There are occasional reports of "rogue" waves of an |
| right? "Assuming" is the name of the city where | | | | even greater ratio |
| Murphy lives. (In case you haven't met Mr. Murphy, you | | | | Therefore, assuming a wave period of 8 seconds, for |
| are an extremely lucky individual!! He lives by the belief | | | | a significant wave height of 10 feet, a wave 19 feet or |
| that what can go wrong, will go wrong at exactly the | | | | higher will occur every 8,000 seconds (2.2 hours). |
| wrong time!!) | | | | We can see that the danger waves pose to a vessel |
| What exactly are waves? How are they formed? | | | | is both a function of the height of the wave and the |
| The waves you see lapping the side of your boat are | | | | period (that is, how frequent the waves come.) If we |
| formed by two sources: | | | | reduce the wave period in half to 4 seconds, then we |
| - Local WIND waves | | | | find that big 19' wave every 4,000 seconds or 1.1 hours. |
| - Distantly generated SWELL waves | | | | If we are out on the open seas for half a day, say 4-6 |
| The wave height is measured from crest to trough, or | | | | hours, chances are very good we will see one of |
| the top of the "hill" to the bottom of the "valley." The | | | | these 19' waves. |
| NOAA computes wave height by the following | | | | This information isn't meant to scare anybody into not |
| formula: | | | | believing the weather service, or deter you from |
| SEAS =√(s^2 + w^2), where S is the height of | | | | enjoying sailing where wave height is of a concern. |
| the swell waves and W is the height of the wind | | | | Keep in mind, however, that nothing is absolute, the |
| waves. If we take a wind value of 7', and a swell | | | | weather changes as fast as predictions are made, |
| value of 7' also and use the formula we come up with | | | | and in the end all we can rely on is our experience and |
| an answer of 9.9' seas. Now, does this mean that no | | | | training. Being well informed is half the battle. The other |
| waves will be over 10'? NO! The National Weather | | | | half is what we do with that information!! |
| Service is fairly conservative in their estimation (for | | | | |