Miriam’s Tropical Sensations

Hurricane Miriam – NHC Advisory 11 (September 24, 2012 at 8:00 a.m. PDT)

The latest expected track for Hurricane Miriam is very favorable for Southern California. As of 8:00 a.m. PDT Miriam has become a major hurricane of category 3 strength, with maximum sustained winds of 120 mph, and is currently moving NW at 12 mph. The official forecast expects Miriam to gradually turn northward and decrease in speed over the next few days, with possible further intensification over the next 12-24 hours.

While the storm is already located in the Southern California swell window, the northward (possibly northeast) turn would focus more swell energy towards Southern California, which is good news for spots that favor moderate-period, south to southeast swell. Keep an eye on the Point Loma forecast and real-time reports, particularly mid-week, which is when the swell’s initial impact is expected to arrive.

Hurricane Miriam – NHC Advisory 13 (September 24, 2012 at 8:00 p.m. PDT)

Update – NHC Advisory 13 as of 8:00 p.m. September 24, 2012:

Hurricane Miriam has started to weaken, with maximum sustained winds now in the 105 mph range (category 2). Additional, slow weakening is expected over the next 48 hours, with hurricane force winds extending outward up to 35 miles from the center. Microwave images indicate that the inner eyewall has collapsed, and the storm has taken on an asymmetric structure, likely due to southwesterly shear. Miriam is still expected to slow and turn north within 48-72 hours, at which time it should weaken below hurricane strength.

As a result of the latest observations, the official forecast has been slightly downgraded. Unfortunately, this means the surf forecast should be downgraded as well. It would have been nice to have major hurricane strength persist as the storm slowed and turned towards California, but it’s looking like Miriam will only make a modest, moderate-period SSE impact later this week.

Hurricane Miriam – NHC Advisory 15 (September 25, 2012 at 8:00 a.m. PDT)

Update – NHC Advisory 15 as of 8:00 p.m. September 25, 2012:

Hurricane Miriam remains a category 2 storm, with maximum sustained winds near 100 mph. The forward speed of the hurricane has been slowing over the last 12-24 hours, and Miriam is currently moving west-northwest at 5 mph. A turn toward the northwest is expected later today, followed by a turn to the north-northwest on Wednesday. Hurricane force winds extend outward up to 35 miles, and tropical storm force winds extend outward up to 115 miles.

The decrease is tracking speed is favorable news in terms of swell production, as is the forecast path, however gradual weakening is expected to continue during the next 48 hours. A mixture of swell periods and directions are clearly visible in Wednesday’s San Clemente Basin forecast, with moderate WNW swell (4-5 feet at 12-13 seconds, 293°), moderate SSW swell (2 feet at 13 seconds, 203°), and moderate SSE swell from Miriam (2-3 feet at 12 seconds, 161°) all concurrently in the water.

Two things to note: (1) Buoy 46086 is located well offshore, and is exposed to much more swell energy than nearshore stations, so observations will be greater than those located closer to land. (2) Real-time primary swell reports over the next few days will likely be dominated by the longer-period WNW and SSW groundswells, but don’t be fooled, the SSE energy is still in the mix, it just isn’t expected to be dominant.

With all that energy in the ocean, expect some fun-sized combo-swell conditions on Wednesday and Thursday, but don’t expect to be sharing epic tales of Miriam with the kids twenty years from now. To truly make the most of the combo-swell conditions, you’ll need to find a spot with exposure to the WNW and SSE angles at moderate swell periods (think Dana Point and Oxnard), otherwise go with the SSE/SSW breaks.

Forecast Southern California/