Lead Forecaster Daniel Crawley
Good Monday morning to everyone, we start a new workweek and the big weather story is Hurricane Ian. After being disorganized and fighting some mid level dry air for a good part of Sunday, Ian really took off Sunday night with the assistance of a nocturnal max of convection around the center. This allowed Ian to intensify quickly and become a hurricane.
As of the 8 am intermediate advisory from the National Hurricane Center, Ian has maximum sustained winds of 75 mph moving northwest at 14 mph. The expectation is for additional rapid intensification over the next 24 hours making Ian a major hurricane as it clips the Western tip of Cuba. It will then move north and over time start to slow down as it approaches the Florida Gulf Coast by mid week, we will go into the synoptic details here in a minute.
A first view of visible satellite imagery shows Ian well defined with curved banding of convection and a strong inner core. the storm is also growing in size as it becomes stronger…
Synoptic Breakdown…
Its looking more and more like Ian is going to be a long duration event for areas that it may impact across the United States, starting with Florida and then moving north into the Interior Southeast US.
One good bit of news as we start Monday is that the computer model guidance is coming together on a solution for the track of Ian. There has been a lot of talk on social media about one specific computer model “caving” or “folding” toward another model solution but instead what we have are individual deterministic outliers that have converged toward a middle solution that has been consistently shown by the model ensembles for a while. This is why you never pin your hopes or put all stock into one specific model run.
The models have come to a solution of bringing Ian NNE from the Western tip of Cuba to a location just west of Tampa Bay by Wednesday. The storm movement will begin to slow down at this point due to weakening steering currents around Ian. This could last for a solid 24 hours or more meaning impacts (winds, rain, surge) to the Florida West Coast could be long lasting.
Once we get to late week Ian will slowly move north and make landfall somewhere on the Western Peninsula or Big Bend Region of Florida. Upper level shear and the slow movement will generally allow the storm to weaken but again, its the long duration that will make matters worse.
By Friday night Ian will be making landfall and at that point, impacts will begin to shift into the Carolinas. Friday will feature a day of mid to high level clouds moving out in advance of the storm and an easterly breeze thanks to pressure gradient. But moisture will quickly invade the region and by Saturday morning, widespread moderate to heavy rainfall is expected across a large part of the Interior Southeast US.
The forecast track of Ian along with a pre-storm surge of moisture due to the east wind has the potential to set up some major problems somewhere across the South. Its too early to nail down the location but someone is going to get a lot, and truthfully, too much rain over a 24-48 hour period.
I have specific concerns for our region as the track promotes a long duration southeast flow into the escarpment region in the Blue Ridge…Southeast winds transporting rich, tropical moisture could reach 60 knots on Saturday.
Picture below is the Precipitation forecast from the Weather Prediction Center through Sunday morning, as you can see a large part of the Southeast could see significant amounts of rainfall. We can narrow down the specifics once we get closer…
Summary…
- Ian will intensify into a major hurricane over the next 24 hours as it moves over Western Cuba.
- Impacts to Florida will begin in earnest on Wednesday and due to the expected slowing down, the impacts could be long duration.
- Landfall occurs late Friday and from there, attention shifts to the flood potential across the inland Southeast. Very heavy rainfall could occur as we see a prolonged southeast flow into the Carolinas.
Its never too early to prepare for impacts across the Western Carolinas. With rainfall being the primary concern, simple chores such as doing maintenance and cleanup on guttering, downspouts, ditches and drains would be smart to help allow water to flow freely. Make sure leaves are not clogging areas where water can flow in and out. The opportunity to do that is now with the weather expected to be calm for the next 3-4 days…
Our region has been dry for the past two-plus weeks so initially the river and lake basins in Western North Carolina will be able to handle the water. But as some point, flooding may become an issue in locations where rain rates are excessive.