25 September 2019

Karen moving away from Puerto Rico, Lorenzo upgraded to 5th hurricane

Karen made landfall on the eastern side of Puerto Rico on Tuesday afternoon as a tropical storm and is now centered about 240 miles north of the island.  As of 11am EDT, the peak sustained winds are 45 mph and it is moving toward the north at 15 mph. The northward motion is expected to continue roughly through Friday, at which point things get messy.

The NHC forecast is in line with most of the model guidance, and shows a stall sometime around Friday, followed by a sharp left turn (there could easily be a little loop in the process) toward the west. That stall-and-turn or loop-and-turn depends on a subtropical ridge building and strengthening to its north, but it also depends on how strong the storm itself is since storms of different intensities are generally steered by different layers of the atmosphere.

Models all agree on a stall and/or loop of some sort, and the large majority show some degree of westward track after that.  But what's not shown on the map above are the intensities.  In some cases, there's barely a trackable system, and there's really no support among dynamical models for anything of hurricane intensity. Clearly, given the potential for impacts in the Bahamas and the southeast US, we'll be watching model trends very closely, but as of now, it's not a cause for concern.

Lorenzo became the season's 5th hurricane on Wednesday morning, and is fully expected to become the season's 3rd major hurricane in a few days.  It is far from land in the deep tropics west of Cabo Verde, and models all agree on a north turn to begin later this week which will keep it out in the middle of the ocean. As of Wednesday morning, the peak winds are 85 mph and the official forecast brings it up to 125 mph (Category 3) by Friday evening.

Tropical Storm Jerry has been transitioned to a post-tropical cyclone, but is still headed toward Bermuda.  It is nearly devoid of rain and thunderstorms, but does have tropical storm force winds associated with it.  It will make its closest approach to Bermuda late Wednesday night. If any rain showers or thunderstorms develop in it, there are radar loops at http://bmcnoldy.rsmas.miami.edu/tropics/radar/. Recall that Jerry formed last Tuesday and peaked as a Category 2 hurricane northeast of the Leeward Islands.

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