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October 2012

Sandy Strengthens to Cat 2, Now Lashing Bahamas, Likely to Become Historic Nor’easter

   Posted by Levi at 4:57pm on October 25, 2012

Hurricane Sandy strengthened at a somewhat unprecedented rate last night, and made landfall in eastern Cuba as a strong Cat 2. Sandy is now back over the water and is lashing the Bahamas as a slightly weaker Cat 2 hurricane. Some restrengthening is likely as the storm moves through the Bahamas, and Sandy could potentially become a Cat 3 hurricane, though due to dry air likely to start plagueing the storm permanently now that the core has been disrupted, the forecast keeps her peak at upper-end Cat 2 intensity. Regardless, the Bahamas will be lashed for at least the next 24-36 hours due to a slowing of Sandy’s forward movement in response to a steering flow change. Thereafter, as Sandy moves away from the Bahamas, her maximum winds are likely to slow, despite the fact that the central pressure will likely remain steady or fall. This will be due to an expansion of Sandy’s windfield, such that the core will not be as tight as it is now. The intrusion of dry air into Sandy’s massive circulation will be partially responsible for this, along with baroclinic influence from a mid-latitude trough to the northwest. Sandy will likely retain hurricane-force winds through her probable landfall somewhere in New England as she begins to take on extratropical characteristics.

Sandy’s track forecast reasoning remains the same as it has been. The current NNE motion should switch gradually to NNW or NW over the next 24 hours as the mid-level ridge axis to Sandy’s north moves by, changing the steering flow temporarily. After 36-48 hours, Sandy should resume a NNE to NE motion as a large mid-latitude trough comes in from the northwest. Due to Sandy’s likely strong northwest side of the circulation at this time, and the 200mb trough to her west that will be following her northeastward, the storm should easily phase with the longwave trough and be drawn back to the north and northwest into New England by Day 5 and 6. The track forecast has not changed much since yesterday, but has acquired greater confidence in the long range. The GFS, which has been flip-flopping terribly, seems to now be finally settling on a landfall solution instead of a northeast track out to sea, a correction that was expected this model would have to make given its mishandling of the baroclinic dynamics. The ECMWF remains the most consistent of all the models, and the forecast track lies fairly close to the ECMWF ensemble mean.

Sandy has the potential to be a very historic storm for New England, and impacts are expected to be severe over a widespread area. Interests in this region should begin preparations for an event that could surpass Hurricane Irene from last year in many areas.

We shall see what happens!