*******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.**********
...FRIDAY SEPTEMBER 30 2022 4:12 AM EDT...
URGENT - Hurricane Ian is located further east of previous forecasts while also stronger... elevating the risk of impacts for the eastern and central Carolinas as well as south-central and southeastern Virginia... see Ian section below for more information.
Elsewhere... Tropical Depression Eleven is in the process of dissipating in the open eastern Atlantic... see remnants of Eleven section below for more information.
In addition... monitoring the following areas for signs of development:
(1) The tropical wave of low pressure that recently emerged from western Africa has increased computer model support showing its development in the eastern tropical Atlantic... see area of interest #34 section below for more information.
(2) A tropical wave of low pressure remains defined over central Africa... computer model support showing its development when it later moves into the Atlantic has dropped. This tropical wave is not considered an area of interest for future development at this time.
(3) The tropical wave of low pressure at 33W longitude is currently inactive and is expected to continue west into the eastern Caribbean Sea in about six days. Meanwhile split flow upper divergence over the eastern Caribbean could increase during that timeframe... between a remnant upper vortex to the northeast associated with the currently decaying string of central Atlantic upper vorticity and souheast side of an upper ridge axis to persist over the northwestern Caribbean Sea. This tropical wave could see an increase in thunderstorm activity due to this upper divergence... therefore this tropical wave may require monitoring for development in the Caribbean in the days ahead.
HURRICANE IAN... In the last 24 hours... Ian's core of rotation as expected proceeded to weaken to a higher-end tropical storm over the east-central parts of the Florida peninsula. While Ian was expected to the recover in the waters offshore of northeastern Florida due to an interaction with the cut-off upper trough incoming from the west... it was not expected to re-strengthen as quickly as it has. In fact Ian has regained hurricane strength almost a day early when compared to my previous intensity forecast...and not only that we have aircraft reconnaissance data as of 11:15 PM EDT that supports maximum sustained winds of 85 mph. The favorable interaction with the cut-off upper trough just west of Ian is as follows... (1) northerly surface flow on Ian's west side is helping to pull cool air associated with the trough southward... (2) to the west of the cut-off upper trough an amplifying central US warm upper ridge wave is being built up by warm southerly flow ahead of a western US frontal system... (3) the two effects are amplifying the cut-off upper trough which is increasing the supportive upper divergence over Hurricane Ian. I assess that Ian's more rapid than expected re-intensification lies with the upper westerly jet just northeast of Ian... supported by the sharp air mass contrast between the current northeast US cold core upper trough and warm core upper ridge axis that stretches across the western and northern Atlantic. Ian's warm southerly flow on its east side in theory should be helping this upper ridge axis amplify. And because the eastward track of Ian allowed it initially weaken less while moving into offshore water sooner... and also closer to this upper ridge axis... perhaps the warm southerly flow supporting the upper ridge axis is stronger than previously thought... in turn further sharpening the aforementioned air mass contrast and leading to a slightly stronger upper westerly jet. In turn... the stronger jet is more effectively pulling air away from Hurricane Ian's top (i.e. enhancing Ian's northern outflow)... helping Ian's surface pressures fall further. And to add more insult to injury in the forecasting world... Ian is yet again east (and also a tad north) of prior forecasts and therefore my updated forecast track is once again nudged eastward as follows:
In the short-term... Ian's track should represent a hook where the current northeast track bends to a more north and then north-northwest trajectory. The hook shape is a result of the cut-off upper trough just west of Ian amplifying further into a cut-off upper vortex (the mechanisms amplifying this trough were explained in the prior paragraph)... with Ian rounding the east side of the vortex. Over the next 48 hours... the hook shape will also be aided by the current surface ridge due north of Ian... followed by a second northern US/Canada surface ridge to quickly replace it by 48 hours (this second surface ridge will be supported by the convergent west side of the current upper trough sliding across northern Canada). My forecast track strategy over the last couple of days is to take Ian's initial position and then have it chase the supportive upper divergence maximum on the east side of the cut-off upper vortex as the GFS model run at the time shows it. Because Ian keep's on staying east of prior forecasts... this results in an eastward shift in my forecast track... even slightly east of the NHC official and GFS at the time of the forecast... and in this update this is also the case with my latest forecast track. The landfall time is also adjusted to be a bit sooner as Ian is also a tad north of the prior forecast as well. I now forecast Ian's center to come onshore toward the northeastern South Carolina coast instead of the central South Carolina coast in this update. Note that by 48+ hours the hook in the track becomes resisted... with the forecast track bending sharply back eastward as a current shortwave upper trough just north of the Great Lakes and southward-digging upper trough to slide from its current northern 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 a broad frontal low pressure area where Ian loses its identity within.
Regarding intensity... due to Ian remaining an over-achiever and the increasingly favorable interaction with the upper wind jet to the northeast and amplifying cut-off upper trough/vortex just to the west... I have raised my intensity forecast. At 24 hours I forecast Ian to be a higher-end category 1 hurricane centered just inland of the northeastern South Carolina coast. In other words I expect Ian to also be a bit stronger than shown at the 24 hour point... at a location just offshore of northeastern South Carolina and just before 24 hours... knocking on the door of category 2. By 48 hours... Ian should complete transition to an inland non-tropical system supported by the eastern divergence zone of the cut-off upper trough/vortex... especially as the landfall removes it from the heat source that is the warm Gulf stream waters. However due to the increased intensity forecast... it will take a bit longer for Ian to spin down and I forecast it could still pack gale force winds (40+ mph) at the 48 hour timeframe.
Regarding impacts to land areas... due to the widespread area of upper-level winds supporting Ian... the hurricane in addition to becoming stronger than expected has also grown in size. Along with the shift in the forecast track... this is resulting in an worsening outlook for wind and coastal storm surge impacts for certain areas (coastal storm surge in particular as Ian's larger size makes it more capable of pushing more water than a smaller storm of equivalent wind strength)... a regional breakdown of the expected impacts is outlined below:
(1) The northeast coast of Florida continues to see gusty tropical storm force winds and coastal surf due to Ian's enlarged size. These impacts will wind down later today as Ian accelerates north.
(2) Gusty winds and coastal surf are currently buffeting the coast of Georgia... also due to Ian's larger size. These impacts will wind down early Saturday once Ian moves further into the Carolinas.
(3) Preparations across all of South Carolina for tropical storm force winds capable of scattered damage should be rushed to completion this morning...albeit the latest forecast track reduces the wind risk for the western-third of the state... however still prepare in this area just in case the track wobbles back west. Preparations in Charleston and inland areas just to the north should consider that winds could reach hurricane force if the track wobbles back more west. Preparations in northeastern South Carolina both coastal and inland should also being considering that winds could reach hurricane force if the current track holds. Those in the hurricane force wind zone will experience a high chance of prolonged power outages and more damage. Along the coast of South Carolina... remain abreast of the latest coastal storm surge forecasts as Ian is already stronger than prior forecasts... if local officials and/or local news media inform you that you need to move to higher ground while it is still safe to do so... due to an increase in the storm surge forecast... please do so... this will be especially true across the eastern half of the South Carolina coast where Ian's wind direction will push water toward shore. And finally... all of South Carolina could be covered with heavy rainfall with flash flooding potential... when encountering a water-covered roadway do not drive into it.
(4) Interests in south-central and southeastern North Carolina should be rushing preparations to completion this morning for winds that could gust as high as top-end tropical storm force... creating a medium chance of prolonged power outages and some wind damage. Areas along and just inland of the coast... from Wilmington to the North Carolina/South Carolina border... should now be ready for potential hurricane force winds that would further increase the potential of prolonged power outages and wind damage. Along the coast of North Carolina... remain abreast of the latest coastal storm surge forecasts as Ian is already stronger than prior forecasts... if local officials and/or local news media inform you that you need to move to higher ground while it is still safe to do so... due to an increase in the storm surge forecast... please do so... this will be especially true across the southern half of the North Carolina coast from Cape Hatteras to the border with South Carolina... which will be positioned closer to Ian's stronger southerly winds that will be more capable of pushing water toward shore.
(5) Interests in north-central and northeastern North Carolina... and across south-central and southeastern Virginia... should now be preparing for tropical storm force winds capable of scattered damage as Ian is forecast to make landfall at a higher intensity and will need more time to spin down while shifting northward further inland. I recommend preparations to finish in this region by no later than tonight. Surf is also more likely along coastal southeastern Virginia.
(6) Heavy rainfall with flooding potential will be a concern later today and into the weekend across North Carolina... Virginia... eastern West Virginia... southern Maryland... and Delaware if the current forecast holds. Coastal surf is now more likely along coastal southeastern Maryland.
The following are wind reports at National Weather Service stations from northeastern coastal Florida to southeastern coastal North Carolina listed in mph over the last several hours:
**Saint Augustine FL... sustained 22... gust 31... now
**Saint Augustine FL... sustained 36... gust 49... 4:56 PM EDT Thursday
**Jacksonville FL... sustained 23... gust 32... now
**Jacksonville FL... sustained 40... gust 53... 5:53 PM EDT Thursday
**Brunswick GA... sustained 26... gust 36... now
**Savannah GA... sustained 17... gust 23... now
**Beaufort SC... sustained 25... gust 38... now
**Charleston SC... sustained 18... gust 31... now
**Myrtle Beach SC... sustained 71... gust 24... now
**Myrtle Beach SC... sustained 18... gust 35... 4:56 PM EDT Thursday
**Wilmington NC... sustained 17... gust 26... now
**Wilmington NC... sustained 25... gust 37... 11:53 PM EDT Thursday
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Sep 30)...85 mph maximum sustained wind hurricane centered just offshore of northeastern Florida at 30.2N-79.3W
IOH 24 Hr Forecast (0000Z Oct 1)...90 mph maximum sustained wind hurricane centered just inland of the northeastern South Carolina coast at 33.8N-79.5W
IOH 48 Hr Forecast (0000Z Oct 2)...Gale-force remnant low centered over north-central North Carolina at 35.8N-79.5W
REMNANTS OF ELEVEN...The tropical depression in the eastern Atlantic continued northwestward toward a developing surface ridge weakness in the central Atlantic... associated with the cold front being driven across the central Atlantic by the current frontal cyclone southeast of Greenland. As it did so... it moves into stronger upper southwesterly shearing flow that more effectively seperated the thunderstorms from the surface swirl of the depression... with this upper flow being driven by the string of upper vorticity in the central Atlantic. The NHC downgraded the depression to a remnant low on Thursday... and in the 0000Z NHC TAFB analysis is further downgraded to a remnant surface trough now lacking a closed circulation. This is my final statement on this system on this blog as it is no longer a tropical cyclone.
AREA OF INTEREST #34...The tropical wave of low pressure that has recently entered the eastern tropical Atlantic from western Africa continues to show signs of organization with rotation in its cloudiness. Moreover the computer model support for this system has quickly escalated... with no models showing development 24 hours ago and now global models agreeing on developing this system into a tropical cyclone at some point. The NHC has introduced this tropical wave as an area of interest in their tropical weather outlook... already assigning a 40% peak odds of tropical cyclone formation for the next five days due to the strong model support. Because this tropical wave was previously associated with area of interest #34 in birdseye view post #114... it is again tagged area of interest #34 in this update for the sake of continuity.
Based on the latest satellite loops I estimate a center of rotation near 10N-17.5W. There is some east-west spread in the forecast track of this system among the models... for example comparing the western ECMWF solution from 1200Z Thursday to the eastern GFS solution from 1800Z Thursday. This is related to where exactly the models see this system consolidating in relation to a pocket of low surface pressure to strengthen over northwest Africa over the next 48 hours... with this pocket to be supported by the eastern divergence zone of a piece of upper troughing over Europe to evolve into a cut-off upper vortex thanks to the current strength of the north Atlantic upper ridge. The closer this system consolidates toward the pocket... the harder it will be for this system to slide west around the Atlantic surface ridge while attracted toward the pocket. For now my forecast track shows an initially slow westward progress around the surface ridge over the next 48 hours. After 48 hours... a chunk of the current northeastern US upper trough will slide east-southeast into the environment of this system due to the strength of a warm upper ridge to build in the western Atlantic (this upper ridge will be bolstered by warm surface southerly flow ahead of Ian... followed by warm southerly surface flow ahead of a broad frontal low pressure area that will materialize with the aid of the complex upper trough to absorb Ian's remnant system). Initially the westerly flow ahead of the approaching upper trough fragment helps to knock away the northwest Africa upper vortex such that the surface low pressure pocket over northwest Africa releases its grip on this system... and I forecast a faster forward speed after 48 hours. In the longer range... the upper trough fragment could turn this system more north in track... especially if it becomes stronger/taller to couple with the upper flow. A hint of an increased northward angle in show in my forecast track below by 120 hours.
Regarding odds of tropical cyclone formation... this system has seen a notable reduction in thunderstorm activity. Just before sunset on Thursday... a beige tinted airmass was seen just north of this system on true-color visible satellite... a sign of dry Saharan air. Perhaps the northwest side of this system has ingested dry Saharan air... therefore I set lower peak odds of tropical cyclone relative to the NHC as of this writing... at 20%. Other than dry air... conditions are otherwise favorable for development as this system will be tucked under a tropical upper ridge axis in the region featuring low shear/upper outflow.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Oct 1)...0% chance of tropical cyclone formation (eastern tropical Atlantic near 10N-21W)
IOH 48 Hr Outlook (0000Z Oct 2)...10% chance of tropical cyclone formation (south of the Republic of Cabo Verde Islands near 11N-23W)
IOH 72 Hr Outlook (0000Z Oct 3)...20% chance of tropical cyclone formation (southwest of the Republic of Cabo Verde Islands near 11.5N-25.5W)
IOH 96 Hr Outlook (0000Z Oct 4)...20% chance of tropical cyclone formation (eastern tropical Atlantic near 12N-29W)
IOH 120 Hr Outlook (0000Z Oct 5)...20% chance of tropical cyclone formatio (eastern tropical Atlantic near 13.5N-32.5W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Sep 29) CMC Model Run...
**For Hurricane Ian... makes landfall over northeastern South Carolina just after 30 hours... weakens to a remnant low over northwestern North Carolina at 48 hours... remnant low turns east across the North Carolina/Virginia border and dissipates just after 72 hours while an offshore large frontal low to the southeast becomes the dominant feature.
**For area of interest #34... tropical wave organizes into a tropical low near 10N-25.5W at 72 hours... tropical cyclone formation suggested near 11.5N-29.5W at 114 hours.
**Tropical wave currently at 33W longitude organizes into a southeastern Caribbean tropical low at 144 hours in split flow upper divergence betweeen an upper ridge axis in the northwestern Caribbean and a remnant upper vortex to the northeast associated with the current string of central Atlantic upper vorticity.
**Surface trough extending southward from Ian and into the western Caribbean Sea becomes better defined thorugh 30 hours while supported by divergence out ahead of the southeast US cut-off upper trough currently interacting with Ian... through 102 hours organizes into a tropical low southwest of the Cayman Islands underneath the low shear/upper outflow of the upper ridge axis in the region... tropical low drifts slowly northwest toward the western tip of Cuba through 168 hours.
1200Z (Sep 28) ECMWF Model Run...
**For Hurricane Ian... makes landfall on the central South Carolina coast between 24 and 48 hours... weakens to a remnant low over western North Carolina at 48 hours... remnant low shifs east into eastern North Carolina through 72 hours and shortly afterwards loses its identity to offshore frontal low located to the east-northeast.
**For area of interest #34... tropical cyclone formation suggested near 11.5N-27W at 96 hours... intensifies into a compact high-end tropical storm near 13.5N-32W at 120 hours.
1800Z (Sep 29) GFS Model Run...
**For Hurricane Ian...makes landfall on the central South Carolina coast at 24 hours... weakens to a remnant low over western North Carolina at 42 hours and loses its identity shortly thereafter to a frontal low that develops further south over Georgia.
**For area of interest #34... tropical cyclone formation suggested near 10.5N-20W at 57 hours... moves into the southwestern Republic of Cabo Verde Islands as a compact hurriacne at 111 hours... curves increasingly north in track and is located just west of the northwestern islands at 126 hours.
1800Z (Sep 29) NAVGEM Model Run...
**For Hurricane Ian... makes landfall on the central South Carolina coast at 24 hours... weakens to a remnant low over northwestern North Carolina at 48 hours... remnant low moves east-southeast to the southeast coast of North Carolina through 84 hours where it subsequently loses identity to an offshore frontal low developing to the east-northeast.
**For area of interest #34... tropical wave organizes into broad tropical low near 10N-20W at 48 hours... large-sized tropical cyclone formation suggested south of the Republic of Cabo Verde Islands at 102 hours... located just southwest of the islands at 120 hours.
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