*******Note that forecast and outlooks in this post are NOT the official forecast from the National Hurricane Center (NHC). They are my own detailed views on the Atlantic tropics based on current observations and latest computer model runs. As such do not make decisions based on my posts...consult news media...watches and warnings from your local weather office...and any evacuation orders issued by local governments to make the most informed and best decisions. Visit the NHC website hurricanes.gov (hurricanes dot gov) for the latest watches/warnings and official forecasts on active tropical cyclones.**********
...THURSDAY SEPTEMBER 29 2022 3:22 AM EDT...
Hurricane Ian now eyeing the Carolinas for a Friday night strike after bringing historical impacts to the southwest coast of the Florida peninsula... see Ian section below for more information. Elsewhere... the wandering tropical low pressure in the eastern Atlantic has finally become Tropical Depression Eleven... see Eleven section below for more information. In addition... monitoring the following areas for signs of development:
(1) The tropical wave of low pressure that was approaching the west coast of Africa 24 hours ago has become a little better organized while featuring a defined area of widespread thunderstorms... as it moves into the eastern tropical Atlantic. None of the models develop this tropical wave as of this writing. However should this wave continue to show signs of organization... will consider re-introducing it as an area of interest for tropical development in my next update as upper-level winds are generally conducive for development in the eastern tropical Atlantic... beneath low shear and upper outflow of a tropical upper ridge in the region.
(2) Models are coming into increasing agreement that a tropical wave of low pressure currently over central Africa will move offshore in the 3+ day timeframe while potentially developing. If this continues... will consider adding this tropical wave as an area of interest in my next update.
HURRICANE IAN... Special update #114A available on the home page of this site chronicles Ian's rapid intensification offshore of southwestern Florida to a top-end category 4 hurricane early Wednesday... and a Wednesday evening update as Ian's core slides northeast across the central Florida peninsula as a weakening inland hurricane. As of 11 PM EDT Ian was downgraded further to a category 1 hurricane with 90 mph maximum sustained winds. Also noteworthy is the hurricane continues to track east of previous forecasts while already located about 1 degree east longitude of the prior forecast at 11 PM EDT... and moreover doppler radar suggests the track of the center is bending more east such that the center could emerge into the Atlantic from Cape Canaveral instead of north of the cape as previously thought. As a result... yet again the NHC and also I have adjusted my forecast track to the east. The further east track appears to be a combo of Ian being blocked from going north by a building surface ridge over the eastern US... with Ian also being tall enough to be pushed by the upper westerly flow in advance of a low-amplitude cut-off upper trough approaching from the western Gulf of Mexico and southeastern US. Ian also is looking a little less like a traditional hurricane and more like a less tropical system supported by the eastern divergence zone of said cut-off upper trough... perhaps explaining how Ian is so well-coupled to the upper westerlies associated with the trough. A hook to the northeast... north... then north-northwest is still expected in the timeframe that is now 24+ hours away. In its interaction as a slightly less tropical feature supported by the incoming cut-off upper trough to the west... northerly flow on Ian's west side will pull the cool air associated with the trough southward. In conjunction with an amplifying central US upper ridge wave to be built up in the warm sector of a western US frontal system... the cut-off upper trough is expected to amplify into a cut-off upper vortex whose eastern circulation helps Ian make the hooking turn. Furthermore a surface ridge to build up over Canada and the northern US... to be supported by the western convergence zone of an upper trough currently sliding eastward from its current position over northwestern Canada... will help Ian make the hook. Because of the eastward shift in the forecast track... the hook is now expected to aim Ian right into the Carolinas instead of southeastern Georgia... see section below titled "regarding impact to land areas" for more information on how the new forecast track affects expectations going forward impact-wise. Note that by 72+ hours the hook becomes resisted... with the forecast track bending sharply back eastward as a current shortwave upper trough over south-central Canada and southward-digging upper trough to slide from its current northwestern Canada position are expected to join up with the cut-off upper vortex that will be steering Ian... resulting in an eastward-shifting complex upper trough that takes Ian's remnants eastward out to sea from the mid-Atlantic United States. The divergence zone of the complex upper trough could be quiet elongated... resulting in Ian's remnants becoming elongated and losing its identity as cohesive system while offshore of the mid-Atlantic US.
Regarding intensity... the tide has finally turned against Ian in the short-term. The upper southwesterly flow that helped the hurricane's northern outflow... which resulted in Wednesday morning's historic intensification offshore of southwestern Florida... has finally overspread Ian enough to shear the hurricane. Evidence of the shear is seen by the loss of the eye and core thunderstorms now lopsided to the northeast half of Ian on infrared satellite pictures. The land interaction with Florida has also hurt Ian. On top of that... Ian's southwestern side has ingested some cooler drier air associated with the cool core cut-off upper trough approaching from the west and large-scale current eastern US upper trough. However after 24 hours the tide will turn back to Ian's favor the shear relaxes and overhead upper divergence increases due to the amplification of the incoming cut-off upper trough into an upper vortex (how this trough amplifies is mentioned in the previous paragraph). Because Ian's latest forecast track brings Ian back over water sooner... I have again upped my longer range intensity forecast and now project Ian to become a category 1 hurricane while moving toward and then into South Carolina. I do not project Ian to become stronger than category 1 in this update as Ian's core will need some time to recover from the shear and land interaction it has had with Florida. Also cooler drier air wrapped into the upper vortex that Ian will be interacting with is expected to dampen Ian's next round of forecast intensification.
Regarding impacts to land areas:
(1) For the Florida peninsula... over the next few hours expect inland hurricane wind damage over the central part of the peninsula to the south of Orlando and north of Lake Okeechobee. I currently expect the hurricane force winds to reach as far east as areas just inland of east-central Florida (just inland... or west of... Melbourne... Cape Canaveral... Daytona Beach) before the core of hurricane force winds dissipates. Over the next 6 to 12 hours... the east-central and northeastern parts of the peninsula will also be buffeted by an area of tropical storm force winds capable of scattered damage... as well as heavy rainfall with flash flooding potential (if encountering a water-covered roadway... do not drive into it). Coastal surf over the next several hours will gradually decrease at the west coast of the Florida peninsula... and increase across the northeast coast of the peninsula where the north side of Ian is pushing wind/water toward shore.
(2) The forecast track of Ian has shifted far south and east enough in the short-term to bring more marked coastal surf to the northwestern Bahamas for today.
(3) The risk of rainfall and tropical storm force wind across southeastern Georgia has reduced per the latest east shift of the forecast track. However coastal surf will remain a concern from now through Friday afternoon. Per previous protocols... interests here should now be completing preparations for tropical storm conditions. Be on guard here in case the forecast track shifts back west toward the area... as the dynamics steering Ian are complex which has resulted in multiple forecast shifts over the last few days.
(4) Per the latest forecast track... South Carolina will also have today to prepare for tropical storm conditions. However given the shift in the forecast track... now all of South Carolina... both coastal and inland areas... will need to prepare for tropical storm force winds capable of scattered damage. Heavy rainfall with flooding potential and coastal surf is a concern. I recommend interests in the vicinity of Charleston and just east to prepare for potentially more damaging hurricane force winds and coastal storm surge... this includes areas inland just north of the Charleston area as Ian has potential to accelerate northward across the area as a hurricane by Friday night. I recommend preparations across all of South Carolina finish tonight... or by early Friday at the latest.
(5) Per the latest forecasts... I recommend interests in coastal and inland areas of southeastern and south-central North Carolina to begin preparing for potential tropical storm force winds with scattered damage potential. Coastal surf across all of the North Carolina coast will also be a concern. I recommend preparations across this region of North Carolina to finish by early Friday.
(6) Heavy rainfall with flooding potential will be a concern by Friday and the weekend across North Carolina... Virginia... eastern West Virginia... southern Maryland... and Delaware if the current forecast holds. Rainfall risk to eastern Tennessee has greatly reduced with the latest forecast track shift.
For a summary of wind reports seen across Florida on Wednesday... refer to special update #114A available on the home page of this site.
Update as of 2 AM EDT... Ian as expected has weakened further... and is now a category 1 hurricane with 75 mph maximum sustained winds whose core is moving toward the Cape Canaveral coast of east-central Florida.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Sep 29)...90 mph maximum sustained wind hurricane centered inland over the central Florida peninsula at 27.5N-81.4W
IOH 24 Hr Forecast (0000Z Sep 30)...65 mph maximum sustained wind tropical storm centered just offshore of northeastern Florida at 29N-80W
IOH 48 Hr Forecast (0000Z Oct 1)...85 mph maximum sustained wind hurricane making landfall on the central South Carolina coast at 32.5N-80W
IOH 72 Hr Forecast (0000Z Oct 2)...Remnant low centered over south-central North Carolina at 35.2N-80.1W
TROPICAL DEPRESSION ELEVEN...The wandering tropical low pressure spin in the eastern Atlantic has finally become a tropical depression after several days of tracking it. The southwesterly shear that has been pushing the thunderstorm tops to the northeast of the surface swirl center relaxed enough as the sprawling cold core upper vortex to its north has begun to weaken remaining cut-off from high-latitude cold air... and the vortex is expected to weaken further to a southwest-northeast elongated string of upper vorticity. The relaxation in the shear allowed the tropical low pressure to produce more persistent thunderstorm activity next to its center such that it is now tropical depression eleven. However the shear is not totally absent as the latest thunderstorm tops are still weighted toward the northeast side of the circulation.
The depression is finally making its way westward around the Atlantic surface ridge due as the remnants of Hermine... which previously was enhanced by the eastern divergence zone of the aforementioned upper vortex... has weakened and lost its grip on the depression as the upper vortex itself weakens. However the remnant surface trough of Hermine still appears to be affecting the depression's track as it also zips westward to the north of the depression while also moving around the Atlantic surface ridge... as the depression has already tracked more north and less westward as if its attracted toward the surface trough. The northwestward track of the depression will then continue as the frontal low currently approaching from Atlantic Canada will create an opening in the Atlantic surface ridge. My updated forecast track is adjusted north and east due to the current position and angle of the depression's current track... and it now seems plausible the depression makes a more north turn into the opening of the Atalntic surface ridge at 48+ hours as it will now be closer to the opening. The more north track forecast also takes the depression more directly into hostile westerly shear on the southeast side of the aforementioend upper vorticity string... and then eventually across to the other side of the upper vorticity string where upper convergence should kill off this system if the forecast track holds. This explains the dissipation by 72 hours and weakening shown at 48 hours. I agree with the NHC's intensity forecast as of this writing which does not show the depression become a tropical storm... because the depression is already in a shear environment and is slated to move into higher shear levels going forward. However it would not surprise me if in the next 24 hours the depression becomes a short-lived tropical storm and before the shear worsens.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Sep 29)... 35 mph maximum sustained wind tropical depression centered at 17.2N-35.6W
IOH 24 Hr Forecast (0000Z Sep 30)... 35 mph maximum sustained wind tropical depression centered at 20N-38W
IOH 48 Hr Forecast (0000Z Oct 1)... 30 mph maximum sustained wind tropical depression centered at 23N-41W
IOH 72 Hr Forecast (0000Z Oct 2)... Dissipated near 25N-41W
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Sep 28) CMC Model Run...
**For Hurricane Ian...center emerges into the Atlantic just north of Cape Canaveral Florida at 42 hours as a tropical storm... while regaining top-end tropical storm strength makes landfall just northeast of the Georgia/South Carolina border at 60 hours... weakens to a remnant low just east of the NC/SC/GA border at 78 hours... broad remnant low slides east across the Carolinas and moves offshore at 102 hours... broad remnant low becomes too elongated east-west by 126 hours to track it as a discernable feature.
**For Tropical Depression Eleven... weakens to a remnant trough near 20N-40W at 42 hours.
1200Z (Sep 28) ECMWF Model Run...
**For Hurricane Ian... makes landfall at the South Carolina/Georgia border between 24 and 48 hours... weakens to a remnant low over northwestern South Carolina just after 72 hours... broadening remnant low turns east across the Carolinas by 96 hours and becomes too elongated in offshore waters by 120 hours to track as a discernable feature.
**For Tropical Depression Eleven... dissipates near 22N-40W at 48 hours
1800Z (Sep 28) GFS Model Run...
**For Hurricane Ian...center emerges into the Atlantic just north of Cape Canaveral Florida at 30 hours as a tropical storm... after doing an erratic southeastward wobble just offshore through 36 hours accelerates norhward to 29.9N-80W by 39 hours... redevelops hurricane strength while making landfall at the Georgia/South Carolina border at 51 hours... weakens to a remnant low over northwestern South Carolina at 69 hours... remnant low quickly dissipates over northwestern South Carolina at 75 hours as a new frontal low to the south dominates.
**For Tropical Depression Eleven... weakens to a trough near 17N-37W at 18 hours
**Tropical wave emerges from western Africa at 66 hours... organizes into a tropical low near 11.2N-21.2W at 99 hours...tropical cyclone formation suggested near 11.5N-22.5W at 138 hours... moves northwest while intensifying into a compact strong tropical storm located just southwest of the Republic of Cabo Verde Islands at 168 hours.
1800Z (Sep 28) NAVGEM Model Run...
**For Hurricane Ian... center emerges into the Atlantic from Cape Canaveral Florida at 18 hours as a top-end tropical storm... regains hurricane strength while centered at 29.5N-79.5W at 30 hours... makes landfall over the central South Carolina coast at 54 hours as a potentially strong hurricane... weakens to a remnant low over the western North Carolina/Virginia border at 78 hours...remnant low slides east across North Carolina through 90 hours... remnant low located just offshore of Virginia at 126 hours.
**For Tropical Depression Eleven... weakens to a trough near 17N-38W at 24 hours.
**Tropical wave emerges from west coast of Africa at 78 hours... organizes into a tropical low just offshore of Africa near 11.1N-18W at 96 hours... tropical cyclone formation suggested near 11.5N-18.5W at 108 hours... tropical cyclone located near 12.5N-19.5W at 120 hours.