*******Note that forecasts 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.**********
...MONDAY SEPTEMBER 19 2022 2:30 AM EDT...
Fiona... now a hurricane... has struck Puerto Rico and the Virgin Islands on Sunday... and is now threatening the eastern Dominican Republic and easternmost Bahamas with forecast hurricane-force conditions for today and Tuesday. See Fiona section below for more information. See area of interest #29 section below for an update on the tropical disturbance in the open central Atlantic. See area of interest #32 section below for a tropical wave of low pressure that may develop midway between the west coast of Africa and Republic of Cabo Verde Islands in a few days from now.
New to this site this year... I will be sequentially numbering up areas of interest for possible Atlantic tropical development. In this scheme... will reset back to #1 at the start of next year (January 2023). The current areas of interest in this blog post are designated #29 and #32 as the other numbers were used in previous birdseye view posts. This scheme is to reduce confusion as Atlantic tropical activity increases during the peak of the hurricane season... when multiple simultaneous areas of interest begin and end which previously required shuffling around the area of interest numbers from update to update.
HURRICANE FIONA...Over the last 24 hours... Fiona obtained hurricane strength while centered just south of Puerto Rico. Subsequently Fiona's track has arced more westward and less northward... resulting in the eye clipping the southwest corner of Puerto Rico instead of moving across Puerto Rico. As of writing the ongoing westward arc in the track has placed the small eye of the hurricane just east of the eastern tip of the Dominican Republic. The feature that was supposed to be responsible for keeping Fiona's north angle in track is cool core north-central Caribbean upper vorticity that has been weakening while remaining cut-off from high-latitude cold air. Perhaps this feature has weakened more than the models expected... and perhaps from Fiona's thunderstorm latent heat release... which resulted in the more westward and less northward angle in the storm's track. The models insist that a more north track will resume soon... and this seems reasonable given that Fiona is now closer to what is left of the upper vorticity. However given that a surface ridge is now moving offshore from eastern North America and due north of Fiona... and that the adjacent upper vorticity is apparently in a weakened state and struggling to lift Fiona north... a south and west adjustment to the short-term forecast track is sensible. In the longer range... steering upper southwesterly flow is expected to increase in Fiona's environment and kick the hurricane on a north and then northeast recurvature. The initial increase in the upper southwesterly flow will be brought on when the current southeast US cut-off upper trough gets pushed offshore and toward Fiona by the current northern upper trough streaming eastward across the US/Canada border region. This northern upper trough then bypasses Fiona to the north after 72 hours... with maintenance of the upper southwesterly flow brought on by the approach of a much stronger and more amplified upper trough to approach from central and eastern Canada. Because of the short-term southwest adjustment in the forecast track... Fiona looks to be more aligned with the southern side and less aligned with the east side of this Canadian upper trough in the long range where the steering flow is more westerly and less southerly. That could mean the final destination for Fiona's remannt non-tropical cyclone... just after the 120 hour forecast period... would be more east toward Newfoundland instead of Nova Scotia or Prince Edward Island. My longer term forecast track is also adjusted accordingly.
Regarding forecast intensity... although Fiona is a good margin above my previous intensity forecast the short-term westward adjustment in the track means increased land interaction with the Dominican Republic. Thus my intensity forecast only has a small upward adjustment. Once Fiona clears the Dominican Republic and the western outflow of the hurricane improves with the dissipation of the adjacent upper vorticity to the west... more rapid intensification of Fiona is likely. I forecast Fiona to peak as a major top-end category 3 hurricane at 48 hours...same intensity as the NHC forecast as of this writing... but the difference being I project this intensity to occur sooner. And with the westward adjusted forecast track... the specter of life-threatening major hurricane conditions for the Turks and Caicos in the easternmost Bahamas is increasing... preparations here and for tropical storm conditions elsewhere in the eastern Bahamas should be completed in earnest by Monday evening. After Fiona's center passes over or just near the Turks and Caicos... I project gradual weakening from 48 to 96 hours as upper southwesterly flow is expected to increase in Fiona's environment as noted in the prior paragraph. The upper southwesterly flow would block the western outflow of the hurricane or even shear it some... however the shear may be mitigated by the storm's forecast northeast acceleration aligned with the upper wind direction which explains the graduated instead of rapid weakening rate in the forecast. Also noted in the prior paragraph... Fiona looks to be more aligned with the south side instead of east side of the major upper trough to approach from eastern Canada at the end of the 5-day forecast period... potentially missing the supportive upper divergence maximum on the east side of the upper trough. Therefore I increase the weakening rate at 120 hours... as Fiona moves over cooler waters and gets some but not most of the benefits of upper divergence on the major upper trough's east side. Fiona is destined to ultimately transition into a strong remnant non-tropical frontal cyclone aided by the east side of the upper trough just after the 120 hour forecast period and potentially strike Atlantic Canada... but exactly where in Atlantic Canada will become more clear in future updates.
Regarding impact to land areas:
(1) For the Virgin Islands... tropical storm force gusts have ended. Heavy rainfall with flash flooding potential and coastal surf will remain hazards for the next few hours.
(2) For Puerto Rico... as tropical storm force winds fade the primary threat switches to heavy rainfall with flash flooding and mudslide potential... as well as coastal surf... for the next several hours.
(3) For the eastern Dominican Republic... due to the more westward and less northern track that Fiona has taken on Sunday... in addition to coastal surf heavy rainfall with flash flooding potential and tropical storm force winds are now imminent tonight and through a good portion of Monday. Hurricane force winds are also imminent for the eastern tip of the Dominican Republic... as well as the north-facing coast of the eastern Dominican Republic where the eye moves over or stays close by.
(4) For the eastern Bahamas... preparations for tropical storm conditions (winds and coastal surf) should be finished by Monday evening. The Turks and Caicos islands are now under a hurricane warning as the eye of a potentially intense Fiona could pass over or nearby on Tuesday... this could be a life-threatening situation and I recommend preparing as such! Preparations in the eastern Bahamas and Turks and Caicos should be completed by Monday evening.
(5) Coastal surf is likely on the shores of the central and western Bahamas if Fiona intensifies as forecast.
(6) Confidence is increasing that Bermuda could see strong hurricane force conditions (damaging winds and coastal storm surge) on Thursday/Friday timeframe. Preparations may need to occur on Tuesday or Wednesday.
(7) I recommend interests in the Canadian provinces of Nova Scotia... Prince Edward Island... Newfoundland... eastern Quebec... and eastern Labrador remain aware of Fiona as it has potential to move into the region as a hurricane-force remnant frontal cyclone this upcoming weekend.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Sep 19)...85 mph maximum sustained wind hurricane centered just east of the eastern tip of the Dominican Republic at 18N-68.1W
IOH 24 Hr Forecast (0000Z Sep 20)...95 mph maximum sustained wind hurricane centered just offshore of the Dominican Republic north coast and just southeast of the eastern Bahamas at 20.5N-70.5W
IOH 48 Hr Forecast (0000Z Sep 21)...125 mph maximum sustained wind major hurricane centered just north of the easternmost Bahamas at 22.5N-71.2W
IOH 72 Hr Forecast (0000Z Sep 22)...115 mph maximum sustained wind major hurricane centered at 25.5N-70W
IOH 96 Hr Forecast (0000Z Sep 23)...110 mph maximum sustained wind hurricane centered just southwest of Bermuda at 30N-66W
IOH 120 Hr Forecast (0000Z Sep 24)...85 mph maximum sustained wind hurricane centered at 39N-55W
AREA OF INTEREST #29...The surface trough of low pressure in the open central Atlantic... being supported by the eastern divergence zone of an upper vortex in the region... has evolved into a weak surface low near 27.5N-46W where upper divergence between the northeast quadrant of the vortex and west side of a current eastern Atlantic upper ridge cell is maximal. The surface low is not impressive at the moment with an area of disorganized showers and thunderstorms on the north side of its circulation. Therefore I set short-term odds of tropical cyclone formation to 0% in the next 24 hours. The GFS model yesterday and continuing into today has insisted that the current northwest Atlantic upper trough will deposit a shortwave upper trough that shifts east into this disturbance... in the timeframe that is now 48 hours away. In addition to the split flow upper divergence between the northeast side of the upper vortex and west side of the adjacent eastern Atlantic upper ridge... the eastern divergence zone of the shortwave upper trough may aid this disturbance during this timeframe... and this is when I set odds of development to 10%. After 48 hours... westerly wind shear over this disturbance will likely be prohibitively too high for tropical development as the shortwave upper trough directly cuts across this disturbance. Furthermore the latest models have trended more north with the current northwest Atlantic upper trough as it laters moves into the northeast Atlantic... with the surface ridge produced by its western convergence zone also being further north and hence further away from this disturbance. This results in a more north and less west track of this disturbance in the longer range... which will move the disturbance right into the shearing mid-latitude westerlies by 72+ hours. I end the outlook at 72 hours by dropping development odds back to 0%.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Sep 20)...0% chance of tropical cyclone formation (central Atlantic near 27.5N-46W)
IOH 48 Hr Outlook (0000Z Sep 21)...10% chance of tropical cyclone formation (central Atlantic near 30.2N-47W)
IOH 72 Hr Outlook (0000Z Sep 22)...0% chance of tropical cyclone formation (central Atlantic near 34N-47.5W)
AREA OF INTEREST #32... Satellite image highlighting a tropical wave of low pressure moving into western Africa from central Africa. Satellite image taken at 0300Z:
A vigorous tropical wave of low pressure that has been over central Africa is making its way into western Africa while featuring an ongoing broad gyre of showers and thunderstorms. I estimate the center of the broad gyre is currently in the vicinity of 11N-4E. Computer models insist that the tropical wave has potential to develop at an unusually north location offshore of Africa... between Mauritania and the Republic of Cabo Verde Islands... in approximately four to five days. While water temps in this area are currently above the 26 deg C threshold needed for tropical cyclone formation... tropical cyclone development is usually precluded in this region by dry Saharan air. However given the insistence shown in the global models... I have initiated this tropical wave of low pressure as an area of interest on this blog... but with low 10% odds of tropical cyclone formation given the climatology that does not usually favor development here.
The eastern divergence zone of the current eastern Atlantic upper trough is expected to keep low surface pressures across northwestern Africa and the Iberian Peninsula of Europe... and the models insist the tropical wave will have a north angle in track across Africa caused by this low pressure field such that it later emerges offshore at a more north location. Even though the Atlantic surface ridge is expected to remain intact in the long range... the models see that this system could quickly develop into a strong/tall enough circulation to continue angling north in track due to upper southwesterly flow on the north side of the tropical upper ridge in the region... and out ahead of a fragment of upper troughing to be left behind by the current eastern Atlantic upper trough. The upper southwesterly flow will produce some shear... however not too high to shunt tropical development.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Sep 20)...0% chance of tropical cyclone formation (western Africa near 12N-1W)
IOH 48 Hr Outlook (0000Z Sep 21)...0% chance of tropical cyclone formation (western Africa near 13N-6W)
IOH 72 Hr Outlook (0000Z Sep 22)...0% chance of tropical cyclone formation (western Africa near 14N-11W)
IOH 96 Hr Outlook (0000Z Sep 23)...0% chance of tropical cyclone formation (west coast of Africa near 15N-16W)
IOH 120 Hr Outlook (0000Z Sep 24)...10% chance of tropical cyclone formation (east of the Republic of Cabo Verde Islands at 16N-21W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Sep 18) CMC Model Run...
**For Hurricane Fiona... weakens to a strong tropical storm while moving northwest across the northern Dominican Republic coast in the next 24 hours... moves across the eastern Bahamas as a strong tropical storm by 42 hours... strengthens into a hurricane while centered just north of the central Bahamas at 72 hours... curves north and then northeast and by 120 hours is located just west of Bermuda at 120 hours as a potentially strong hurricane.
**Tropical wave currently south of the Republic of Cabo Verde Islands becomes stationary while tugged by larger and stronger tropical wave approaching from western Africa (area of interest #32)... while stationary organizes into a tropical low near 11.2N-25W through 66 hours... drifts west and becomes a tropical cyclone near 12N-27.5W at 126 hours
**For area of interest #32...Large and strong tropical wave currently over western Africa emerges from west coast of Africa at 84 hours... organizes into a tropical low midway between Mauritania and Republic of Cabo Verde Islands through 126 hours.
1200Z (Sep 18) ECMWF Model Run...
**For Hurricane Fiona... moves northwest across the north coast of the Dominican Republic through 24 hours... while turning more north passes just east of the eastern Bahamas at 48 hours... while accelerating north-northeastward passes just northwest of Bermuda at 120 hours as a potentially strong hurricane
**For area of interest #32... tropical wave emerges from west coast of Africa just before 96 hours... tropical cyclone formation suggested just northeast of the Republic of Cabo Verde Islands at 120 hours... tropical cyclone turns northwest and reaches 21N-22.5W at 144 hours... while drifting north into cooler water the tropical cyclone begins to weaken and reaches 23N-23.5W at 168 hours
1800Z (Sep 18) GFS Model Run...
**For Hurricane Fiona... wobbles west onto the east tip of the Dominican Republic through 15 hours... subsequently turns north-northwest and passes just east of the eastern Bahamas through 42 hours as a compact hurricane... turns north and then northeast with the center passing just northwest of Bermuda at 108 hours as a potentially strong hurricane... reaches 36N-59.5W at 120 hours.
**For area of interest #32... tropical wave emerges from west coast of Africa at 81 hours... organizes into a broad tropical low midway between the west coast of Africa and Republic of Cabo Verde Islands through 105 hours... tropical low drifts north-northwest and reaches 20N-22W through 168 hours where it weakens to a surface trough
1800Z (Sep 18) NAVGEM Model Run...
**For Hurricane Fiona... moves northwest across the north coast of the Dominican Republic through 24 hours... moves northwest into the eastern Bahamas at 42 hours while strengthening further... located just northeast of the central Bahamas at 72 hours as a larger and potentially intense hurricane... accelerates northeast with the center passing just northwest of Bermuda at 114 hours... located at 35.5N-62W at 120 hours.
**For area of interest #32... no development shown