BIRDSEYE VIEW POSTS

Since 2012 on the Weather Underground (www.wunderground.com) blogs, I have been posting annotated "birdseye view" charts of the Atlantic basin, with a detailed explanation and forecasting that references the chart. From there you may know me as "NCHurricane2009." While I now do these "birdseye view" posts here, I will continue to do comments via Disqus on Weather Underground at www.wunderground.com/cat6. You can see my Disqus feed at this link for my latest comments. Feel free to reply to me with your disqus account or e-mail at IOHurricanes@outlook.com 

 
 
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MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #78

*******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.**********


...SATURDAY AUGUST 1 2020 8:57 PM EDT...

See Tropical Storm Isaias and tropical depression ten sections below for all active tropical cyclones in the Atlantic basin. See area of interest section below for the central Atlantic tropical wave of low pressure being monitored for development.


TROPICAL STORM ISAIAS...It appears over the last 24 hours Isaias essentially became a compact tropical cyclone...with a small central core of thunderstorms with outer bands of activity to the northeast of this core. Meanwhile activity west of this core has been limited by southwesterly shear being generated by upper vorticity in the region. When the small core moved over Andros Island in the western Bahamas earlier today...it was too much for the small hurricane to handle in conjuction with the shear...so now Isaias has weakened to a tropical storm. However the tropical storm is just below hurricane force while firing a new central burst of thunderstorms after emerging from Andros Island and maintaining 70 mph maximum sustained winds. Conditions in the next 24 hours will deteroerate along the east Florida coast as the core of Isaias is expected move near or over the coast.


Even though Isaias has been on par with my previous track forecasts...I have adjusted my updated forecast points to be southwest of my previous to be in more agreement with the latest model runs. This shift in the track forecast is apparently due to the more amplified nature of the approaching central United States upper trough than previously shown in the models...which apparently has meant the surface ridge weakness to be created by the eastern divergence zone of the upper trough will be slighlty further to the west. Regarding intensity...I have lowered the intensity forecast as Isaias apperas to have become a small tropical cyclone struggling against the vertical wind shear in the region as well as land interaction from Andros Island...thus I now show Isaias maintaining 70 mph maximum sustained winds for much of the forecast. Yesterday's 1200Z GFS and today's 0000Z CMC have suggested Isaias could re-strengthen while moving away from the Florida coast and toward the Carolina coast...perhaps attributed to lessened southwesterly shear as the incoming upper trough becomes more amplified...so it wouldn't suprise me if Isaias regained hurricane status by 48 hours. I show a lower intensity at the end of the forecast period as models now show the more amplified upper trough generating a seperate frontal low pressure center west of Isaias that will dominate as the dominant non-tropical feature...whereas before Isaias was supposed to transition to the dominant non-tropical feature in the region. Thus wind impacts across New Brunswick...Nova Scotia...and Prince Edward Island by Wednesday may not be as high as previously thought.


See bulletins at the home page of this site for impacts regarding the western Bahamas and United States east coast. Due to the COVID-19 virus emergency ongoing across the southern United States....if you must retreive storm preparation supplies in a crowded setting along the southeastern United States coastal regions...wearing a mask and frequent hand sanitizing will reduce your risk of contracting COVID-19. Also I would suggest thinking about the use of a family/friend residence or hotel location further inland if you live in an area prone to coastal storm surge in case you may have to relocate as the storm approaches and details of exact impacts become clearer...as a public shelter may not be as ideal for controlling your exposure to COVID-19.

******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********

0 Hr Position (1200Z Aug 1)...70 mph maximum sustained wind tropical storm centered just west of Andros Island in the western Bahamas at 25.1N-78.7W

IOH 24 Hr Forecast (1800Z Aug 2)...70 mph maximum sustained wind tropical storm centered offshore of northeastern Florida at 28N-79.5W

IOH 48 Hr Forecast (1800Z Aug 3)...70 mph maximum sustained wind tropical storm making landfall on the South Carolina coast at 32.5N-79.5W

IOH 72 Hr Forecast (1800 Aug 4)...70 mph maximum sustained wind tropical storm centered over the southeast New Jersey coast at 39.5N-74.5W

IOH 96 Hr Forecast (1800Z Aug 5)...Remnant frontal low centered over New Brunswick at 47N-66.5W


TROPICAL DEPRESSION TEN...As the Atlantic subtropical surface ridge has rebuilt in the wake of a departed northeast Atlantic frontal cyclone...tropical depression ten has curved increasingly westward in track while passing north of the Republic of Cabo Verde Islands. It is in an environment of cooler water temperatures and dry saharan air and has lost thunderstorm activity...therefore it will likely be declared dissipated by the National Hurricane Center by 11 PM EDT. This is my final statement on tropical depression ten unless for some reason it is still a tropical cyclone by tomorrow.

******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********

0 Hr Position (1800Z Aug 1)...30 mph maximum sustained wind tropical depression centered north of the Republic of Cabo Verde Islands at 19.5N-23.5W

IOH 24 Hr Forecast (1800Z Aug 2)...Dissipated near 21N-26W


AREA OF INTEREST #1...The north end of a central Atlantic broad tropical wave of low pressure is showing increased thunderstorm activity in the vicinity of 17.5N-55W while interacting with the eastern divergence zone of a developing cut-off upper vortex to the northwest. The warm upper ridge in the western Atlantic is expected to push the upper vortex westward and away and overspread this disturbance...which will keep upper winds quiet favorable for development by keeping wind shear low and upper outflow high. Thus I agree with the high 60% odds of development from the 2 PM EDT National Hurricane Center outlook. By 96+ hours...I nudge odds of development downward as the upper trough forecast to recurve Tropical Storm Isaias north and northeast merges with the upper vortex while keeping the vortex pushed toward the disturbance...which will likely begin to increase some wind shear. Forecast track of this disturbance is straightfoward...a west-northwest to northwest trajectory around the southwest side of the Atlantic surface subtropical ridge. The forecast track keeps this system away from land areas...passing between the Caribbean Islands and Bermuda...and offshore of the eastern United States.

******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (1800Z Aug 2)...25% chance of tropical cyclone formation (just northeast of the Lesser Antiles near 19N-60W)

IOH 48 Hr Outlook (1800Z Aug 3)...40% chance of tropical cyclone formation (western Atlantic near 22N-65W)

IOH 72 Hr Outlook (1800Z Aug 4)...60% chance of tropical cyclone formation (western Atlatnic near 25N-70W)

IOH 96 Hr Outlook (1800Z Aug 5)...45% chance of tropical cyclone formation (western Atlantic near near 31N-72W)

IOH 120 Hr Outlook (1800Z Aug 6)...35% chance of tropical cyclone formation (western Atlantic near 35N-72W)


...COMPUTER MODEL SUMMARY...

Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)


0000Z CMC Model Run...For Tropical Storm Isaias...shown to make landfall on the southeast Florida coast in 24 hours...weakens to a tropical storm on the south Florida peninsula through 36 hours...curves northward and emerges onto the coast near the Florida/Georgia border by 60 hours...continues northeast along Georgia and South Carolina coasts through 72 hours as a reorganizing tropical storm...makes landfall in southeastern North Carolina by 78 hours...moves across southeast Virginia by 84 hours...moves into southern New Jersey by 90 hours...passes just east of New York City by 96 hours...while moving across Maine in 114 hours quickly weakens and loses its identity to frontal low pressure forming to the west. For tropical depression ten...loses its identity just northeast of the Republic of Cabo Verde just after 18 hours. For area of interest #1...north end of broad tropical wave of low pressure becomes a low pressure center in the western Atlantic near 26N-68W in 78 hours...surface low located west of Bermuda near 33N-67.5W in 120 hours.


0000Z ECMWF Model Run...For Tropical Storm Isaias...located just offshore of east-central Florida in 48 hours...makes landfall near the South Carolina/Georgia border just after 72 hours, moves rapidly north-northeast and reaches the coast of Virginia by 96 hours...weakens considerably by 120 hours while entering New Brunswick from Maine while frontal low pressure to the northwest dominates. For tropical depression ten...loses its identity in next 24 hours. For area of interest #1...north end of broad tropical wave of low pressure fractures into a seperate surface trough in the western Atlantic near 25N-66W in 72 hours...develops into a surface low near 31N-70W in 96 hours...located near 35N-69W in 120 hours.


0600Z GFS Model Run...For Tropical Storm Isaias...located just offshore of east-central Florida in 30 hours...located along or just offshore of the northeast Florida coast in 48 hours...makes landfall in northeastern South Carolina in 66 hours...moves across eastern North Carolina and southeast Virginia through 78 hours...reaches southern New Jersey in 84 hours...centered over Rhode Island in 90 hours...centered over the Maine coast in 96 hours while maintaining strength...weakens over southern New Brunswick in 102 hours...begins to lose its identity over Newfoundland in 120 hours. For tropical depression ten...loses its identity to the north of the Republic of Cabo Verde Islands in 12 hours. For area of interest #1...north end of broad tropical wave of low pressure fractures into a seperate small surface low north of the Lesser Anilles near 21N-60.2W in 42 hours...located at 30.5N-71W at 120 hours.


0600Z NAVGEM Model Run...For Tropical Storm Isaias...makes landfall in southeast Florida in 30 hours...moves northward and emerges back over water from northeast Florida in 60 hours...strengthens into an intense hurricane and makes landfall over Cape Fear North Carolina in 84 hours...reaches east coast of New Jersey in 102 hours...over eastern Massachusetts in 108 hours...moves into Maine while maintaining strength in 114 hours...over New Brunswick in 120 hours. For tropical depression ten...loses its identity northwest of the Republic of Cabo Verde in 24 hours. For area of interest #1...no tropical cyclone formation shown

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