*******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.**********
...SUNDAY SEPTEMBER 18 2022 2:53 AM EDT...
Tropical Storm Fiona currently lashing the Virgin Islands with tropical storm conditions... and will soon produce strong tropical storm winds over Puerto Rico later today. See Fiona section below for more information on the tropical storm. See area of interest #29 and #30 sections below for an update on the pair of tropical waves of low pressure located well east of Tropical Storm Fiona and in the tropical Atlantic. Elsewhere... a tropical wave of low pressure over central Africa... in the vicinity of 5E longitude... remains defined on satellite imagery. The current global model consensus suggests some development of this wave as it later moves into the eastern tropical Atlantic in about four days. This tropical wave could emerge as another area of interest in future updates if these trends continue.
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 #30 as the other twenty-eight were mentioned 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.
TROPICAL STORM FIONA...The westerly shear being applied by the current north-central Caribbean upper vorticity onto Tropical Storm Fiona... located in the northeastern Caribbean as of this writing... has reduced as evidenced by the thunderstorm activity better covering the center of circulation and also the activity being notably better organized compared to 24 and 48 hours ago. Visible satellite imagery and Doppler radar imagery from the Virgin Islands suggest an almost symmetric instead of sheared storm... however when switching to colorized infrared satellite there are still signs of shear with the shield of strongest thunderstorms still lopsided to the east half of the circulation. Fiona has maintained 60 mph maximum sustained winds over the last 24 hours... however there are signs the storm is trying to strengthen with the storm reaching its lowest surface pressure so far (997 mb) as of 11 PM EDT coupled with the fact Doppler radar and infrared satellite animation suggest a northwest turn in the direction of Puerto Rico has begun. The northwest turn signals the storm is becoming strong/tall enough to now be steered by the north-central Caribbean upper vorticity... and I have no choice but to now shift the forecast track notably east of where I put it yesterday. Based on the currently-observed angle of the northwest track... my new forecast track is lined up with the more eastern 1800Z GFS and NAVGEM model runs where the center of circulation passes over Puerto Rico instead of the east coast of the Dominican Republic. Once the steering cool core Caribbean upper vorticity dissipates just after 48 hours (while remaining cut-off from high-latitude cold air)...a more north and then north-northeast track is expected due to upper southwesterly flow out ahead of an upper trough to approach from the US/Canada border region. Although this upper trough will then bypass Fiona to the north after 96 hours... a north-northeast track through 120 hours is expected to be maintained by the upper southwesterly flow ahead of a much stronger and more amplified upper trough to approach from central and eastern Canada.
Regarding forecast intensity... for the next 24 hours I think it will be a close call as to whether or not Fiona reaches category 1 hurricane strength before crossing Puerto Rico. For my updated forecast... I assume Fiona doesn't quiet reach hurricane strength in the short-term as the shield of storm activity on colorized infrared satellite is struggling to wrap around into the west side of the circulation due to the lingering shear. However as the shearing Caribbean upper vorticity fades away through 48 hours... I predict an increasingly more rapid strengthening rate and forecast Fiona to peak as a major category 3 hurricane at 72 hours. Because the upper trough to approach from the US/Canada border region will entangle with the current southeast US cut-off upper trough and become tilted southwest-northeast as a result... there will be an increase in upper westerly flow pushing into Fiona's west side where it would block the western outflow of the hurricane or even shear it some... thus I project gradual weakening from 72 to 96 hours. I project additional gradual weakening of Fiona from 96 to 120 hours as the upper westerly flow continues on the south side of the upper trough as it bypasses Fiona to the north. Due to the more amplified nature of the subsequent Canadian upper trough... wind shear may reduce just after 120 hours... with the tremendous divergence zone and southerly flow on the east side of the upper trough helping to maintain Fiona as a hurricane-force non-tropical frontal cyclone over cooler waters while swinging Fiona into Atlantic Canada.
Regarding impact to land areas:
(1) For the northern Lesser Antilles... tropical storm force winds and heavy rainfall have ended. Coastal sea swells should reduce through Sunday and early next week.
(2) For the Virgin Islands... tropical storm force winds are arriving as the Saint Croix US National Weather Service station recently reported a gust to 43 mph. Coastal sea swells and heavy rainfall with flash flooding potential will also be hazards for the next 24 hours.
(3) For Puerto Rico... tropical storm force winds will arrive later this morning. Some wind damage potential is possible as the island will be exposed to the storm's strongest winds as the center passes over or nearby. Coastal sea swells and heavy rainfall with flash flooding potential will also be hazards for the next 24 hours.
(4) Interests in the eastern Dominican Republic should have finished preparations for tropical storm conditions by now. The combination of the storm's current northwest angle in track and lingering westerly wind shear in the region is likely to keep the heaviest rainfall and strongest winds east of the area. However coastal sea swells and some gusty winds cannot be ruled out in the next 24 hours.
(5) The potential for heavy rainfall across the western Dominican Republic and Haiti has ended with the latest shift in the forecast track.
(6) Eastern Cuba is not expected to see impacts from Fiona due to the lastes shift in the forecast track.
(7) For the Bahamas... the western islands are not likely to see notable impacts from Fiona due to the lastest shift in the forecast track. The central and eastern islands are likely to see coastal sea swells as Fiona strengthens into a potentially strong western Atlantic hurricane after this weekend. The eastern Bahamas should remain on guard in case Fiona's track undergoes a westward shift or wobble after clearing Puerto Rico and the Dominican Republic... which could expose the eastern Bahamas to gusty winds.
(8) Bermuda should closely monitor the progress of Fiona as it has potential to pass over or just west of the island as a potentially strong hurricane by Wednesday.
(9) I recommend interests in the Canadian provinces of Nova Scotia... Prince Edward Island... Newfoundland... eastern Quebec... and eastern Labrador become aware of Fiona as it has potential to move into the region as a hurricane-force remnant frontal cyclone by the latter part of this upcoming week.
Update as of 2 AM EDT... aircraft reconnaissance finds that Fiona has strengthened to 65 mph maximum sustained winds with the surface pressure dropping to 994 mb. Making no change to my intensity forecast outlined below at this time. Gusts recorded at Saint Croix in the Virgin Islands have increased a little further while now reaching 44 to 48 mph.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Sep 18)...60 mph maximum sustained wind tropical storm centered just south of the Virgin Islands at 16.6N-64.9W
IOH 24 Hr Forecast (0000Z Sep 19)...70 mph maximum sustained wind tropical storm centered just northwest of Puerto Rico and just northeast of the eastern Dominican Republic at 19.2N-67.5W
IOH 48 Hr Forecast (0000Z Sep 20)...90 mph maximum sustained wind hurricane centered east of the eastern Bahamas at 22.5N-69.5W
IOH 72 Hr Forecast (0000Z Sep 21)...115 mph maximum sustained wind major hurricane centered at 25.5N-70.5W
IOH 96 Hr Forecast (0000Z Sep 22)...110 mph maximum sustained wind hurricane centered southwest of Bermuda at 29N-68W
IOH 120 Hr Forecast (0000Z Sep 23)...105 mph maximum sustained wind hurricane centered just northwest of Bermuda at 33N-66W
AREA OF INTEREST #29...The north side of a central Atlantic tropical wave of low pressure located well east of Tropical Storm Fiona is evolving into a surface trough of low pressure being maintained by divergence on the east side of a nearby upper vortex. The surface trough is not impressive at the moment while featuring a fan of clouds... showers... and some thunderstorms removed to the north of the trough by southerly shear imparted by the upper vortex. As a result I have dropped short-term odds of tropical cyclone formation to 0%... and also lower longer term odds of tropical cyclone formation to 20% thus coming into agreement with the NHC tropical weather outlook as of this writing. By 72 hours...the major upper trough currently approaching from eastern Canada will have lodged a cell of central Atlantic upper ridging into the eastern Atlantic. A more focused area of upper divergence between the northeast corner of the upper vortex and northwest side of this eastern Atlantic upper ridge cell may allow for the surface trough to develop into a surface low...and this is when I increase development odds to 10%. Once the major upper trough shifts northeastward and away into the northeast corner of the Atlantic at 96+ hours... the eastern Atlantic upper ridge cell and remainder of the western Atlantic upper ridge have potential to bridge over this disturbance... providing a better upper outflow and lower shear environment needed for tropical development. This is when I raise odds of tropical cyclone formation further to 20%. An increasing turn to the west is depicted at 72 and 96 hours as this disturbance rounds the north side of the upper vortex and responds to a building surface ridge to the north to be supported by the western convergence zone of the departing major upper trough. At 120 hours southerly flow ahead of Fiona to approach from the southwest is expected to curve this system back to a northward track. Just after that timeframe... especially should Fiona transition into a sprawling non-tropical frontal cyclone as currently forecast... this system will likely be absorbed into the east side of Fiona.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Sep 19)...0% chance of tropical cyclone formation (central Atlantic near 23N-45W)
IOH 48 Hr Outlook (0000Z Sep 20)...0% chance of tropical cyclone formation (central Atlantic near 26.5N-45W)
IOH 72 Hr Outlook (0000Z Sep 21)...10% chance of tropical cyclone formation (central Atlantic near 27.8N-47W)
IOH 96 Hr Outlook (0000Z Sep 22)...20% chance of tropical cyclone formation (central Atlantic near 28.5N-51W)
IOH 120 Hr Outlook (0000Z Sep 23)...20% chance of tropical cyclone formation (central Atalntic near 33N-51W)
AREA OF INTEREST #30...The tropical wave of low pressure currently moving toward the central tropical Atlantic from the eastern Atlantic has seen a reduction in thunderstorm activity. Before sunset a renewed surge of dry Saharan air to the northeast... seen as a beige tint in the true-color visible satellite scheme... may explain the wave's reduction in activity. Global models continue to not develop this tropical wave. In addition in the longer range... the upper vortex currently interacting with area of interest #29 is more likely to get pushed south by Fiona's outflow and toward this tropical wave where it would suppress upper outflow and increase wind shear... as Fiona is trending more east in track and stronger in intensity in the latest model guidance. Therefore I have dropped this tropical wave's odds of development to 0%... and plan this to be my final statement on this area of interest on this blog.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Sep 19)...0% chance of tropical cyclone formation (eastern tropical Atlantic near 10N-38.5W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Sep 17) CMC Model Run...
**For Tropical Storm Fiona... begins to quickly intensify just south-southwest of Puerto Rico at 18 hours and turns northwest into and across the north coast of the Dominican Republic through 48 hours where the strength of the storm levels off due to land interaction... continues northwest across the eastern Bahamas through 78 hours... strengthens into a hurricane just north of the central Bahamas at 102 hours... turns north and reaches 27N-74.5W at 120 hours.
**For area of interest #29... no development shown
**For area of interest #30... no development shown
**Tropical wave emerges from west coast of Africa at 108 hours... organizes into a broad tropical low midway between the west coast of Africa and Republic of Cabo Verde Islands through 144 hours... tropical low located just northeast of the Republic of Cabo Verde Islands at 168 hours.
1200Z (Sep 17) ECMWF Model Run...
**For Tropical Storm Fiona... reaches strong tropical storm strength just southwest of Puerto Rico at 24 hours... moves northwest across the north coast of the Dominican Republic through 48 hours... turns increasingly north and passes just east of the eastern Bahamas through 72 hours as a compact hurricane... reaches 27N-72W at 120 hours.
**For area of interest #29... no development shown
**For area of interest #30... no development shown
**Tropical wave emerges from west coast of Africa at 120 hours... tropical cyclone formatino suggested just northeast of the Republic of Cabo Verde Islands at 144 hours... tropical cyclone turns northwest and reaches 21N-23W at 168 hours.
1800Z (Sep 17) GFS Model Run...
**For Tropical Storm Fiona... intensifies into a compact hurricane while turning northwest into Puerto Rico through 18 hours... passes just northeast of the Dominican Republic northeast coast through 39 hours and just east of the eastern Bahamas through 54 hours... while becoming a large and potentially intense hurricane reaches waters just southwest of Bermuda at 120 hours.
**For area of interest #29... no development shown
**For area of interest #30... no development shown
**Tropical wave emerges from west coast of Africa at 108 hours... organizes into a broad tropical low midway between the west coast of Africa and Republic of Cabo Verde Islands through 132 hours... tropical low drifts north-northwest and reaches 20N-21.5W through 168 hours.
1800Z (Sep 17) NAVGEM Model Run...
**For Tropical Storm Fiona... while gradually strengthening turns northwest across Puerto Rico through 18 hours... reaches hurricane strength while passing east of the eastern Bahamas at 48 hours... while becoming a large and potentially intense hurricane reaches waters just southwest of Bermuda at 120 hours.
**For area of interest #29... no development shown
**For area of interest #30... no development shown