10 October 2018

Category 4 Hurricane Michael poised to make historic landfall on Florida panhandle today

Similar to Hurricane Harvey last August, Michael went from a tropical storm to a Category 4 hurricane in the two days leading up to landfall.  But what makes this even worse is that the Florida panhandle has never experienced a Category 4 hurricane in recorded history.  The magnitude of the destruction from wind and storm surge will be unprecedented in this area.

Some of the most notorious major hurricane landfalls in the region were Opal 1995, Ivan 2004, and Dennis 2005, but all of them weakened from Cat-4s to Cat-3s as they approached the coast.  Michael is still strengthening.

Landfall, defined to be when the center crosses the coastline, is expected to occur around 2pm EDT today, but the storm is much  more than a landfall point of course.  Heavy rainbands and building storm surge are already impacting hundreds of miles of coastline, and conditions will deteriorate rapidly during the day. Peak storm surge levels could be 14 feet just east of the landfall point and destructive winds will plow well inland through Alabama, Georgia, and even South Carolina and North Carolina tomorrow.

You can monitor storm surge at select stations at https://tidesandcurrents.noaa.gov/quicklook/view.html?name=Michael
and I have several long, updating radar loops at http://andrew.rsmas.miami.edu/bmcnoldy/tropics/radar/

Looking much further east, Leslie is a hurricane again, and although it's been 18 days since it formed, it shows no signs of leaving the picture.  Yesterday, most models were suggesting it would become extratropical and head toward Portugal/Morocco, but now more are falling into line with a turn toward the south and back into the Atlantic.  So, it could be around for another week or two.

Tropical Storm Nadine has already made the anticipated northward turn and is forecast to dissipate this weekend.

09 October 2018

Hurricane Michael strengthens as it heads for a Florida landfall on Wednesday

Michael is now a Category 2 hurricane and poised to strengthen even more during its final day before landfall.  Little has changed in the forecast or expected impacts, which means a major hurricane is likely going to hit a part of the coastline that has very little experience with such things.

As of 8am EDT, peak winds are up to 100 mph and it's centered 265 miles west of Key West FL and 390 miles south of Panama City FL.  The storm has a decent chance at another round of rapid intensification today, meaning that it can strengthen a lot in a short amount of time due to conducive environmental conditions.

Hurricane Threats and Impacts graphics for Hurricane Michael as of Tuesday morning. (NOAA)
The hazards associated with a hurricane include wind, storm surge, flooding, and tornadoes.  As of Tuesday morning, the maps above summarize the spatial extent of these hazards, with the "cone of uncertainty" overlaid.  Note that the cone only relates to the probable track, and is not at all meant to depict impacts.  NOAA made these Hurricane Threats and Impacts (HTI) graphics operational in June 2015 and they've been available for every storm since then... you can find the current versions at https://www.weather.gov/srh/tropical or https://digital.weather.gov/.

The rainfall swath and amounts look typical for a landfalling hurricane, and flash flooding is likely along its inland trajectory.  The storm surge however, is amplified in this area, so even a Category 1 or 2 hurricane can produce surges of 10 feet or more in Florida's 'Big Bend'.  Zooming in on an inundation forecast map shows the extent of significant surge that is expected.

The total water level, or storm tide, is maximized when the regular tides and the storm surge act in concert.  Landfall is predicted sometime in the early afternoon hours on Wednesday, and some regional high tide cycles are as follows:
11:00pm (tonight) and 10:30pm for Panama City
4:40am and 6:10pm for Apalachicola
2:50am and 3:40pm for Cedar Key
While the tidal range isn't huge in these places, every foot or two can make a difference when it comes to what gets flooded and what doesn't.


Tropical Storm Leslie is gradually strengthening again, and is forecast to regain hurricane status on Wednesday.  It is in virtually the same place it was when it formed on September 23, but is now destined to make a final exit toward the Azores and then Portugal/Morocco this weekend. While definitely rare to have a tropical or recently-post-tropical cyclone hit this area, it's not unprecedented.  Vince hit Portugal as a tropical storm in October 2005, a handful of post-tropical cyclones have hit Portugal, and Delta ran into Morocco in November 2005 shortly after becoming extratropical.

In the deep tropics, the easterly wave that exited the African coast on Saturday has been upgraded to Tropical Storm Nadine.  Peak winds are estimated to be 40mph and it's centered about 500 miles southwest of the Cabo Verde islands.  However, it's going to turn north and run into higher wind shear and cooler water by the weekend and that will be the end of it -- long before it has a chance to get near anything.

Enhanced infrared satellite loop of TD15. (CIRA/RAMMB)

07 October 2018

Tropical Depression 14 forms and is expected to become Hurricane Michael this week

The large disturbance we've been watching for at least a week finally became a tropical cyclone on Sunday morning... Tropical Depression 14 is centered 100 miles east of the central Yucatan peninsula and is drifting northward at 3mph.  It is forecast to become a tropical storm today, at which point it will be named Michael.

Enhanced satellite image of TD14 on Sunday morning. (CIRA/RAMMB)
By Saturday morning, models had come into remarkable alignment and all showed a tropical storm or hurricane intensifying in the Gulf of Mexico and reaching the northern Gulf coast around Wednesday (if you missed it yesterday, this was my update on Twitter).  This agreement has only solidified since then, and all models now indicate a hurricane making landfall between MS and the eastern FL panhandle on Wednesday. The NHC forecast showing the most likely arrival time of tropical storm force winds is included below (latest available here).  Tropical storm warnings are in effect for the northeast corner of the Yucatan peninsula as well as far western Cuba.

Once the lead time closes in a little more, storm surge guidance will become available for the Gulf coast.  There will definitely be several feet of storm surge in the northeast Gulf coast... exactly when the peak arrives and where the maximum will be will come into clearer focus with time. But the surge-prone Big Bend area of Florida is a sure bet for coastal flooding.

As always, rainfall will be a large threat from this, with a heavy swath from the FL panhandle then up into GA, SC, NC, and VA.  Note that Florence-soaked coastal North Carolina could see quite a lot of rain from this as well.  Gusty wind and heavy rain are fairly likely up into PA, NJ, and the Delmarva region on Thursday.

One-week rainfall forecast, valid from Sunday morning through next Sunday morning. (NOAA/WPC)
I suspect that hurricane and storm surge watches will be issued for parts of the northeast Gulf coast on Monday morning, but stay tuned to NHC forecasts and advisories especially if you're in this area.

02 October 2018

Watching Leslie in central Atlantic and disturbance in western Caribbean

Leslie formed way back on September 23 as a subtropical storm, and since then, it transitioned to an extratropical cyclone of hurricane intensity, back to a subtropical cyclone, and then to a tropical cyclone.  Maximum sustained winds are up to 65 mph and it could soon become the season's sixth hurricane.  It is centered about 540 miles east of Bermuda and tracking toward the southwest; it's forecast to loop back on itself... again.  To say the track has been meandering would be an understatement. And we'll probably still be talking about it next week!

Meanwhile, a cluster of thunderstorms is festering in the western Caribbean... south of Jamaica. There has been a growing consensus from the models that this could become Michael in the coming week.

Enhanced infrared satellite loop over the central Caribbean. The flashing white dots mark lightning flashes. (weathernerds.org)
The models also agree that the evolution will be slow, and this blob could take a while to get organized... if it ever does. But by the end of the weekend, it will likely have drifted northward toward Cuba.  It's way too early to say anything about a track beyond Cuba, and we've got plenty of time to watch it. *IF* it's destined for south Florida, it could reach that area by Tuesday-Wednesday.  At this time, no models are indicating significant intensification.