Thu Sep 06 2018 05:26 AM
Florence, Olivia, 95L, Isaac, Helene. Dangerous Week.

9:30 PM EDT 10 September 2018

Florence is undergoing an eyewall replacement cycle tonight, which will temporarily halt deepening (and max wind speed increases - could even weaken a little), but this is a normal part of a mature hurricane's nature, and will likely help lead to an overall increase in size, with pressure falls/wind speed increases resuming after.

There are several things to fear with Florence. Those along and just inland along the coast of her track need to leave evac zones promptly, as the surge potential is deadly high - even well inland (Say nothing of the winds). Those further inland will contend with a prolonged duration catastrophic wind event and inland flooding. Comparisons being made for a potential Hazel or Katrina ... that then slows down or even sits in place ... are not hyperbolic.

Elsewhere, Invest 95L approaching the west to northwest Gulf of Mexico is odds-on to become a tropical storm, or at least a T.D. And potentially a very wet one. This could bring abundant rain to a portion of the country that has already seen flooding over the past week or so. The next name on the list in the Atlantic is Joyce. Watches and Warnings may be issued at any time.

In the central Pacific, Olivia is now a very strong Tropical Storm, approaching the islands from the east, and likely to make a more-or-less direct hit on the archipelago. The mountains of these islands really squeeze out the precip of even passing afternoon showers, and thus, deadly flash flooding, rock and mudslides are a huge risk.

Isaac weakened some today, the smaller cyclone being battered by some shear and in the vicinity of some dry air. Still forecast to impact the Antilles by Thursday night as a very strong tropical storm.

In the far eastern Atlantic, Helene is still expected to turn north away from land, for now.

9:30 PM EDT 9 September 2018
Issac will likely become a hurricane tonight, Helene already did today.

An area in the West Caribbean has a 30% chance to develop in the Gulf of Mexico and may impact Texas late this week.

And area near the Azores has a 40% chance to develop.

Isaac likely will impact the lesser Antilles this week.

Helene is likely to stay out to sea.

And Florence seems to be zoning in on North Carolina for a major impact Thursday night.

4:30 AM EDT 9 September 2018
Recon dropsonde data from Florence was assimilated by the 0z model runs last night. There is simply no good news that came out from the improved forecasts, outside of increased confidence in the reliability of the NHC forecast. But one which is ugly: the likelihood of a landfalling Major next week somewhere along the southeast coast (and looking more and more like South or North Carolina, but still too early to say for sure - don't even let your guard down just yet in N Florida, Georgia, etc.).

This is a "Red Alert" for those who live in the NHC Cone of Uncertainty. Take all the time you need right now to protect life and property. The NHC forecast is looking increasingly likely. In the event the forecast verifies, the last thing you want is to be rushed.

Elsewhere, dropsonde data was also assimilated into the model runs on Olivia in the eastern Pacific, also resulting only in more confidence of the existing NHC forecast there.

2:00 PM EDT 8 September 2018
Invaluable data from this morning's non-tasked recon mission into the cyclone, timely data from a solid microwave satellite pass, and greatly improved structure in conventional satellite, all suggest that Florence is primed to enter Rapid Intensification. Odds favor an intensification phase ensuing later today, perhaps especially so overnight, and it is not out of the question that Florence is a significant hurricane once again by late tonight, and maybe even a Major by Monday morning.

This improved structure, with better vertical alignment and hints at deepening convection, all point to the cyclone perhaps being able to better feel the gentle pull to round the southwest corner of the High building in to her north and northeast. A slightly rightward (less west) shift in several of the models today has already occurred, and this looks more possible (could be verifying before our very eyes). Now the bad news - the High is still strong and stubborn, and even a trend to the right does not necessarily mean a trip out to sea prior to landfall/s later next week, and no one along the east coast should be letting ones guard down.

8:30 AM EDT 8 September 2018
Florence still generally moving west, and regaining some strength slowly today, but won't really gain much until a few days from now. Models still have a wide spread from Florida to out to sea, but seem to be favoring near the SC/NC border. Shifts are expected, but which direction is unsure. Everyone from Florida to New Jersey should be watching Florence closely. Where will it go? It's all a guess at this point, check out the Forecast Lounge for some thoughts and models.

A NOAA P3 plane is out sampling the air around Florence to help with forecasts starting today.

Helene has prompted a hurricane watch for the Cabo Verde islands with the new forecast.

T#9 is likely to become Isaac sometime today.

Olivia is still forecast to move over the Hawaiian islands as a tropical storm.

6:30 AM EDT 7 September 2018
Florence has weakened overnight, but is forecast to move into a much more favorable area for development in the next 2-3 days. In the meantime that unfortunately means it will likely get to move more west than north (and maybe even slightly south) as the ridging above the system builds.

All of the main 3 model families GFS, Euro, and UKMET that folks are watching have shifted left, more west, with the likelihood of a US impact going up. However it is still too early to tell exactly where the storm will wind up, other than those from Florida all the way to New England should monitor Florence. Only a fraction of the ensembles take it out to sea at this point.

Between Georgia and Virginia in particular is the general area where most of the models converge right now, but that may shift south or north. If the model timelines remain relatively consistent, direct impacts could be felt around Thursday of next week.

Beyond this, both 92L and 93L are at 90% to develop in the next day or so, and those will also need to be watched, but a lot of their future track depends on where Florence winds up.

Two other U.S. threats we are watching - Olivia in the Pacific as a potential threat to Hawaii, and also 26W, which is forecast to hit Guam as a Super Typhoon.

Original Update

September continues producing very high Accumulated Cyclone Energy, or ACE, in both the Atlantic and Central-Eastern Pacific basins, with multiple risks for the U.S. and several of our neighbors. Now that Gordon is well-inland and weakening, but not without a continuing rain threat for the middle of the country, our attention quickly turns to several others potentially just as, if not more, significant tropical threats. The biggest of these being Hurricane Florence in the Atlantic, and Hurricane Olivia in the Pacific.

In the Atlantic, Florence, most recently a powerful Cat 4 Major that is now on a weakening trend in the short term, has the forecasters at NHC doing double time to nail down her future track, with this morning's update shifting more to the west, and a little bit closer to mainland United States.

In the Pacific, Olivia, recently on a strengthening trend again, is forecast to change from her present west-northwestward heading to nearly due west, with increasing concern for potential impacts on the Hawaiian islands early to middle of next week.

Elsewhere, way east in the Atlantic we are also following Invest 92L, which will likely become EIGHT at any time today or tomorrow, as well as yet another vigorous wave about to roll off the west coast of Africa.

Join us in the Forecast Lounge as we delve into analysis of various model outputs on each of these features. We'll see you there!


For Florence:


NCDOT Travel info map, closures, etc

For Isaac:

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