Hurricane Florence Rapidly Intensifying, Likely to Hit North or South Carolina Thursday
Florence has rapidly intensified into a dangerous Category 4 hurricane, and appears destined to strengthen even further as it heads towards the Southeast U.S. Coast. Florence is likely to make landfall on Thursday evening or Friday morning on the coast of North Carolina or South Carolina, and the odds continue to increase that Florence will stall on Friday and meander near or over the coast for several days, making the hurricane a devastating rainfall and coastal flooding threat. Update: at noon EDT, Florence was upgraded to Category 4 strength based on hurricane hunter data. Top sustained winds were near 130 mph, with the estimated central pressure down to 946 millibars, a full 15 mb lower than the estimate from 11 AM EDT.
Florence was about 580 miles south-southeast of Bermuda at 11 am EDT Monday morning, moving west at 13 mph. Sea surface temperatures (SSTs) were a warm 29°C (84°F), which is about 2°F above average. Florence was embedded in an atmosphere with dry air (a mid-level relative humidity of 50%). However, with wind shear a light 5 – 10 knots, the hurricane has successfully walled off this dry air, and is now minimally affected by it. Satellite images on Monday morning showed that the storm was significantly more organized, with a prominent eye, a more symmetrical shape, impressive spiral banding, and a strong upper-level outflow channel to the northeast. Florence was a medium-sized hurricane, with tropical storm-force winds that extended out up to 140 miles from the center. This was 25 miles farther than on Sunday morning.
There is no recent hurricane hunter data from the core of the storm, though the NOAA jet is currently engaged in a dropsonde mission to help out the 12Z cycle of models. These will come out between noon and 3 pm EDT today. A NOAA hurricane hunter aircraft will fly a research mission out of Bermuda late Monday morning, and regular hurricane hunter missions by the Air Force will begin on Monday evening. The NOAA jet will fly another dropsonde mission on Tuesday. Special balloon launches are being performed across much of the central and eastern U.S. over the next few days to double the frequency of upper air data for the models to crunch. In short, we should have steadily improving model forecasts of just where Florence will go.
Intensity forecast for Florence: expect a Cat 4 by Tuesday
Florence’s environment is very conducive for intensification. The SHIPS model predicts shear will remain low through Wednesday night. SSTs will remain near 29°C (84°F) during this period, and ocean heat content will be high, near 35 – 50 kilojoules per square centimeter. Our top intensity models unanimously predict strengthening of Florence into a Category 4 hurricane by Wednesday, and the storm is also expected to increase in size. Florence will still be embedded in a relatively dry atmosphere, so it is possible the storm could suffer from dry air intrusions that would interfere with the intensification process, but this will likely not occur until Thursday, when wind shear is expected to increase to a moderate 10 – 15 knots.
Hurricane Florence is now a Category 4 storm and is “rapidly strengthening” as it heads toward the Carolinas coast, with “exceptionally heavy rain,” the National Hurricane Center said Monday morning.
In an noon update sent out by NOAA, the storm’s winds rose from 105 mph winds to 130 mph in a matter of hours, and it has picked up speed in its westward trajectory, from 9 mph to 13 mph.
“Further strengthening is anticipated and Florence is expected to be an extremely dangerous major hurricane through Thursday,” said a National Hurricane Center statement.
There is potential for tremendous rainfall amounts over the next seven days from Hurricane Florence in the Carolinas and much of the Mid-Atlantic region; courtesy NOAA/WPC
Overview
All eyes are focused on Hurricane Florence as we begin the new week and chances for a major impact on the US east coast continue to grow. Florence is now churning slowly towards the US east coast as a category 2 hurricane and may make a landfall late Thursday or early Friday somewhere along the Carolina coastline – likely with “major” hurricane status. Very strong high pressure ridging is now building at upper levels of the atmosphere across southeastern Canada and the northwestern Atlantic and this will be a key player in the push of Florence towards the east coast over the next few days. In addition, this very strong high pressure ridge will eventually act as an “atmospheric brick wall” for Florence once it reaches the east coast and the brakes will be put on any attempt at a northward advance by the storm. This eventual slow down in the northward advance of Florence will allow for an extended period of heavy rainfall and the result could be tremendous rainfall amounts in the Carolinas and much of the Mid-Atlantic region.
Latest positions of Florence, Isaac and Helene in the very active Atlantic Basin; courtesy NOAA/NHC
ATLANTA (AP) — Rapidly intensifying Hurricane Florence could strike a direct and dangerous blow anywhere from the Carolinas to the Mid-Atlantic region later this week.
Florence crossed the 74 mph threshold from tropical storm to a hurricane Sunday morning, and by evening its winds were up to 85 mph (140 kph) as the National Hurricane Center warned a hurricane hunter plane found the storm strengthening quickly. Forecasters said Florence was expected to become an extremely dangerous major hurricane sometime Monday and remain that way for days.