The worst thing I can think of is a Cruising Boat getting caught in the middle of the Sea of Cortez when the north wind kicks up. I did it once and decided I needed to learn a few more things about Predicting Mexican Weather. I hope this will help a few people out.

The Sea Of Cortez from the months of November to May can and does have a clear sky-high wind system caused by a High Pressure system in the Great Basin region of the United States. This can last from 2 to 5 days at a time, with North to Northwest winds from 20kns to 50kns. The Sea is known for its short and very steep wave action. With very high winds and 10 to 15 foot waves that can get into a life threatening or boat damaging situation fast. So hear is what I have learned from the school of getting my rear kicked.

First the Great Basin is the high plateau east of the Sierra's and west of the Rocky Mountains including most of Nevada and Utah. Around late October the Pacific High slides south allowing low-pressure systems to move thru the Northwest region of the U.S. When the cold front of these system passes the Rocky Mountains it allows an over pressurization to fill in the Great Basin. This sets a condition called Santa Anna Winds. These winds pass thru the passes of the Sierra's to the Pacific and down the Sierra's and Rockies between California and Arizona and into The Sea of Cortez. This normally happens two to three days after the low-pressure system clears the Rocky Mountains. There is normally a 24-hour time lag in the Sea from time the Santa Anna starts in California and the beginning of the high winds in the Sea. The same with the calming of the winds. In the mid-winter months the storm systems start back up in the North Pacific and start moving thru the northwest in a faster cycle normally causing more but shorter Santa Anna conditions. Then in late winter the cycle slows down causing fewer but more intense wind conditions. When late winter or early spring arrives the deserts of the southwest starts warming up and a Thermal Low begins to build over the Yuma area of the U.S. These are non-weather low- pressure systems. They are caused by warm air rising from the warming deserts of the Southwest. The Yuma low blocks the Santa Anna winds from interring the Sea of Cortez. In late winter or early spring the Yuma Lows are knocked out by another Pacific storm moving thru the Southwest and opening the Sea for another Santa Anna blow. Then by Mid April or early May the Pacific High moves north forcing the North Pacific storms to move thru Northern Canada and ending the cycle of the Great Basin High and allowing the Yuma Low to fill in as a full time Low blocking the North Winds.

That is Why and now things to watch for.

1. Pacific Low Pressure Systems moving thru Northwest from November thru May
2. High Pressure filling over Great Basin area.
3. Santa Anna Winds blowing in California. (Remember 24 Hr. Time Lag)
4. Large Pressure Gradient between San Diego and La Paz (Higher in San Diego)
5. Thermal Low building over Yuma (Cruisers best friend)

A few things I have learned over the years by my Mexican Fisherman Friends most of the times they know more than the experts.

1. If you see Mares Tail Clouds this is a good sine of Northers coming within 24 Hr.
2. If Shrimpers don't go out at night sleep in tomorrow.
3. If the wind starts a night sleep in late.

Hope this will help out all the New Cruising people in the Sea of Cortez. The one thing I think every boat should have on board is either a Ham Radio or a Ham Receiver. The Cruising Ham Nets are the best place to get up to date Weather. The people running these Nets have been doing this for years and are very knowledgeable about Mexican Weather and local conditions for the waters of the Sea of Cortez. If you are New to the Sea just ask any of the Cruising Community for help or advice they will be glad to help you out. Fare Winds and be Safe

Capt Juan
S/V Wand-rin Star