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Pacific Hurricane Season Ho-Hum: Blame the Cool Water

| posted on July 22, 2010

El Nino and La Nina play a definite role in the intensity of both the Atlantic and Pacific hurricane seasons. That large area of warmer or cooler water off the coast of NW South America has some unreal affects on worldwide weather, especially tropical activity. Generally tropical activity will be suppressed in one ocean or the other. Rarely will you get enhanced activity in both oceans. A strong El Nino tends to increase the activity in the Eastern North Pacific due to warmer waters in the area. On the other hand El Nino will decrease activity in Atlantic since associated southwesterly flow throughout the area creates shear that prevents or inhibits development. This year we have gone back to a neutral year. This along with other factors is contributing to a very active Atlantic season while the Eastern North Pacific has been rather uneventful with only one swell-generating hurricane so far, excluding Hilary.

One other factor is causing problems for NE Pacific hurricanes. Waters off the tip of Southern Baja are much cooler than normal right now. And when tropical development is concerned, a few degrees means quite a bit. This pool of cooler water can probably be blamed on a few things. First, we had a very abnormal winter. Contrary to many TV Weathecasters it was NOT El Nino’s fault. That sure does pull in the viewers though. This was actually caused by a large, persistent blocking high in the Gulf of Alaska, which caused the jet stream to over amplify all the way into Southern California and further at times. This event, plus typical springtime N winds, appears to be the culprit. This build up of cooler water begins almost exactly where Southern California’s swell window opens up. Along 20N latitude (even with Manzanillo) the extreme eastern side of the swell window begins around 113W, which will send in swell from 160 degrees. Unfortunately this is almost exactly where the water becomes too cool to sustain a tropical system.

Hurricane Hilary: Right now it is Monday afternoon at 3pm PDT. Hurricane Hilary is almost directly over the general area I mentioned above. Convection (tstorm development) in the NW quadrant of the storm is already looking much worse than even a few hours ago due to this cooler water. It has begun a weakening trend already and looks to continue to do so as it holds on a WNW path. Ideally, if this water were 80 degrees Fahrenheit, it could keep strengthening and supply us with perfect 8 to 10’ punchy, 12 wave set, peaky, barreling hurricane swell– haha. We should see some swell, but right now it’s looking mainly in the 2-4’ range for select areas (steep 155-175). Check the Wavewatch.com tropical updates and your local forecast for details.