Update at 3:46 p.m. ET. Sandy Makes Landfall:

At 3:20 p.m. ET., Sandy made landfall about five miles east of Kingston, Jamaica, the Hurricane Center said in an update.

Our Original Post Continues:

The tropical cyclone Sandy has just crossed the threshold to become a hurricane.

As of the 11 a.m. ET. National Hurricane Center advisory, Sandy had winds of 80 mph and was moving north-north-east at 13 mph. It was just off the coast of Jamaica, where it is expected to make landfall later today. By Friday it will have moved across Cuba, and it is forecast to be somewhere off the east coast of Florida.

The Hurricane Center has issued a tropical storm watch for the peninsula that extends from Volusia/Brevard county line south to the upper keys.

Weather.com reports that "heavy rain, flash flooding and mudslides" are likely as the storm trudges through Cuba and Jamaica.

As for the United States, Florida and the Carolinas, Weather.com reports, are likely in for just some heavy surf.

One forecast scenario for early next week, however, could mean some fairly rough weather for New England and the Mid-Atlantic:

"Another track scenario is much more ominous for the East Coast."In this case, a so-called "blocking pattern" in the upper levels of the atmosphere over the Atlantic is so strong that it would not allow the storm to turn east into the open Atlantic, but, rather, drive northward just off the East Coast."Furthermore, the upper-level trough in the polar jet stream we referred to above would provide an additional turbo-charged boost to this low, producing an intense, East Coast storm!"

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