Irene Watch: Second Rapid Intensification Cycle may be Beginning

Although major hurricane Irene has been struggling a bit with too many islands in its’ path creating unstable circulations in its’ fractured eyewall, it has continued to slowly improve its’ overall satellite presentation in the last day of two. This afternoon (Thursday, 1 PM), the storm has healthy outflow in all directions and a well-rounded central dense overcast, though the vertical structure of that CDO is a bit ragged. It may have undergone one eyewall replacement last night as it crossed the Central Bahamas, and today, as it crosses Grand Bahama, it is definitely undergoing another replacement – very visibly changed center-points and reforming the eyewall in the last two hours. These kinds of things are common even in intense hurricanes, but particularly when the eye is over land.

The central pressure of Irene continues to hover near 950 mb, but as the storm lifts north away from the islands, I expect pressures to fall further and the CDO to re-flare one last time. Starting tomorrow around midday, the storm will begin feeling the effects of the westerlies with WSW shear increasing over the storm from 5-10 m/s to 20 m/s as it nears Cape Hatteras Saturday. The shear will initially cause the storm to become more asymmetrical, and eventually cause it to weaken, but only slowly, as it is a very large circulation and will take time to spin down.

The trend westward with track continues in today’s modelling, suggesting that the heaviest rains may get back into the I-95 corridor south of Philly a little further than I was thinking last night. A large area of greater than 3 inches of rain will overspread the coastal plain from southern North Carolina to interior upstate New York and all points east…however the heaviest rain, which will be in excess of 10 inches, will be confined to a band from eastern NC through the Old Dominion of Virginia, Lower Southern Maryland, the DelMarVa Peninsula, the Phi9lly metro area, most of the state of New Jersey, lower Upstate New York and far Western New England.

The strongest winds with the storm will be felt on the3 outer banks of North Carolina and in the southern Tidewater of VA, however, hurricane force winds also seem likely in extreme coastal new Jersey and most of Long Island, at least in gusts. The further inland track than earlier forecasts had suggested implies lesser impacts for eastern New England, where there had been concerns for hurricane conditions prior to last night.

However, a large area of 20-30 foot waves and 5-10 foto storm surges will impact the outer banks of North Carolina, the Tidewater of Virginia, the Southern coast of the DelmarVa Peninsula, all of coastal New Jersey and all of the southern Coasts of Long Island, as well as Nantucket, Block Island, Martha’s Vinyard (take THAT, Obama!!) and Cape Cod. Although the storm is expected to weaken to a category one hurricane by the time it makes final landfall in Long Island of coastal New Jersey, it will have carried a wall of water that gained momentum from earlier, stronger parts of it’s history, and because it’s such a large storm, a large area will be affected.

Many in Long Island were around to witness Hurricane Gloria, which impacted very near the current forecast landfall site and did tremendous damage even to western Long Island. I expect impacts form this storm to be similar…perhaps a tad worse in spots due to the shear size of the circulation of Irene. As level-headed as I tend to be during weather disasters (and as much as I make fun of people running to the store to buy toilet paper and bullets every time there’s a storm), even I’m going tonight to acquire emergency provisions in case I am without power for an extended period of time. I recommend anyone in the affected coastal locales do the same.

One thought on “Irene Watch: Second Rapid Intensification Cycle may be Beginning

  1. UPDATE: 8 PM EDT Thursday 08/26

    Irene, now fully away from the Bahamas, is indeed showing signs of gathering strength. The eye has decreased in size, as has the Central Dense Overcast, though there is still a large circulation overall and the storm still possesses a wide swath of outflow and feeder bands. As well as shrinking its' core, the storm has become much less ragged and better rounded in all quadrants, and hurricane hunters have found that the central pressure has fallen 5 mb in the last three hours to 946 mb.

    Based on the continued health and power of the storm's much smaller and more complete single eyewall, I believe it is about to undergo a rapid intensification that will carry it to category four intensity. The stronger the storm gets now, the more power it will have behind it as it moves up the coast and weakens, so this bears watching.


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