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BIRDSEYE VIEW POSTS

Since 2012 on the now retired Weather Underground 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 at Yale Climate Connections via Disqus where the former Weather Underground community has moved to. Feel free to reply to me there, at my Disqus feed at this link, or via e-mail at IOHurricanes@outlook.com 

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MY 2023 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #58

Updated: Aug 21, 2023

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


...SUNDAY AUGUST 20 2023 12:45 PM EDT...

The Atlantic tropics remain hyperactive while a series of tropical waves of low pressure spanning from the eastern Caribbean to eastern Atlantic… supported by the outflow of a lengthy tropical upper ridge... are being monitored for signs of tropical cyclone formation. See area of interest  #21... #23.. and #24 sections below for more information. Two of these waves have become tropical cyclones… see T.D. Six section below for one of them. The other cyclone is area of interest #21 which was recently upgraded to Tropical Storm Emily.


Elsewhere... the tropical wave of low pressure currently in the northwestern Caribbean is moving toward the Gulf of Mexico where it will have development potential… see area of interest #22 section below for additional details.


Note that the forecasts and outlooks below were completed at 0600Z earlier today. Any changes they have occurred with each area of interest or active tropical cyclone since then are noted on each respective section below.


TROPICAL DEPRESSION SIX... The tropical low pressure in the low-latitudes of the central Atlantic was able to become the sixth cyclone of the 2023 Atlantic Hurricane Season by 5 PM EDT Saturday while firing a burst of strong thunderstorms that covered its center. This development was probably aided by the passage of the system directly below the regional tropical upper ridge axis where shear is lower. As of late it is apparent that the depression has reached the other side of the ridge axis where westerly shear is now present between the axis and the western Atlantic upper vorticity… as evidenced by the thunderstorms being pushed to the east of the swirl center. As a result it is forecast to soon weaken to a remnant low. Models have trended with a less northward angle regarding the forecast track… which is sensible for a weaker/shallower system that would be less tugged by the western Atlantic upper vorticity… and my updated forecast track below is adjusted accordingly. With this latest forecast… impacts to the northern Lesser Antilles from this system are likely to be negligible.


Update as of 11 AM EDT… In the face of westerly shear… tropical depression six has been able to fire a thunderstorm burst that now covers the center. Therefore the depression may last a little longer than shown in my forecast below.

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

0 Hr Position (0600Z Aug 20)... 35 mph maximum sustained wind tropical depression centered at 17.2-51.5W

IOH 24 Hr Forecast (0600Z Aug 21)... Remnant low centered at 17.7N-56W

****** National Hurricane Center (hurricanes.gov) official forecast as of 5 AM EDT****************************

Loss of tropical cyclone status (0600Z Aug 21)… 30 mph maximum sustained wind remnant low centered east of the northern Lesser Antilles at 17.3N-56.8W


AREA OF INTEREST #21 (RECENTLY UPGRADED TO TROPICAL STORM EMILY)... The eastern Atlantic tropical wave of low pressure... which continues to feature a large gyre of showers and thunderstorms... has continued to become better organized while now featuring a core of thunderstorms over and north of its center. Therefore I assess that this system is likely to become a tropical cyclone shortly and so I have begun a track and intensity forecast as outlined below. As of 0600Z the center of the this system was north of the previous forecast and so my updated one is adjusted accordingly. This system through 48 hours should continue to have a northward angle in its westward track due to a surface ridge weakness associated with the eastern divergence zone of the current western Atlantic upper vorticity. Between 48 and 72 hours the track is accelerated westward... with less of a northward angle... as this system bumps into what will be remaining of the Atlantic surface ridge during that timeframe. The track then bends north again by 96+ hours while turning into the western Atlantic surface ridge weakness to be associated with the current upper trough and surface frontal system pushing into central Canada… as that frontal system later breaks into the Atlantic.


Regarding forecast intensity… this system has been able to organize in the currently light southerly shear environment and appears to be on its way to tropical storm status… and my intensity forecast below reflects this. By 48 hours as this system nears the string of upper vorticity lurking to the north…. it will encounter stronger and more westerly shear and so I forecast weakening during that timeframe. The upper wind outlook looks better for 72 and 96 hours as the upper vorticity in the western Atlantic shifts east toward this system as an amplified upper trough whose eastern divergence zone potentially enhances this system. At the same time this incoming upper trough is now forecast to be more eastward… or closer to this system… which may disrupt the western half of its circulation… and so I only show a slight recovery to the intensity during this timeframe. By 120 hours (5 days) the north track pulls this system away from the upper trough and into more favorable warm core upper ridging with low shear and upper outflow… associated with the warm surface southerly flow ahead of the aforementioned incoming frontal system. Therefore I conservatively show some slow strengthening by day 5 as it is unclear if this system will survive in the shorter term shear before it gets to this haven. If indeed this system does survive to take advantage of the better day 5 conditions… it’s conceivable it could strengthen faster than shown below.


Update as of 11 AM EDT… this system has been upgraded to Tropical Storm Emily with 50 mph maximum sustained winds. I have increased the shorter-term intensity forecast accordingly… and for the short-term I do not anticipate Emily to strengthen over 50 mph due to the current light southerly shear environment.

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

0 Hr Position (0600Z Aug 20)... Tropical low centered in the eastern tropical Atlantic at 18.8N-37.5W

IOH 24 Hr Forecast (0600Z Aug 21)... 50 mph maximum sustained wind tropical storm centered in the eastern tropical Atlantic at 20.2N-39.5W

IOH 48 Hr Forecast (0600Z Aug 22)... 35 mph maximum sustained wind tropical depression centered in the central Atlantic at 21.7N-42.5W

IOH 72 Hr Forecast (0600Z Aug 23)... 45 mph maximum sustained wind tropical storm centered in the central Atlantic at 22.7N-47.5W

IOH 96 Hr Forecast (0600Z Aug 24)… 45 mph maximum sustained wind tropical storm centered in the central Atlantic at 28N-51W

IOH 120 Hr Forecast (0600Z Aug 25)… 50 mph maximum sustained wind tropical storm centered in the central Atlantic at 33N-51W

******National Hurricane Center (hurricanes.gov) official forecast as of 11 AM EDT*****************************

Loss of Tropical Cyclone Status (1200Z Aug 22)… 35 mph maximum sustained wind remnant low centered in the central Atlantic at 22.5N-45.8W


AREA OF INTEREST #22... A large western Caribbean tropical wave of low pressure continues to traverse westward... now heading for the southern Gulf of Mexico from western Cuba. The southwest edge of the current Atlantic surface ridge is expected to push the wave west-northwest into the Gulf over the next 24 hours. After that time an amplified upper trough will be moving into eastern Canada from central Canada... with the western convergence zone of this trough building an eastern North America surface ridge. The southwest side of this ridge will continue the west-northwest trajectory of the tropical wave toward the Texas/Mexico border region. Showers and thunderstorms across the north apex of the tropical wave have increased while now in alignment with the outflow of a Gulf of Mexico upper ridge cell. Also noting this upper ridge cell is and will continue to expand as restrictive upper vorticity that was in the way is already retrograding into Texas and Mexico while pushed around the central US upper ridge. Due to ongoing computer model support showing at minimum a tropical low forming in the north apex of the wave… and the increase in showers and thunderstorms noted above… I agree with the NHC raising peak odds of tropical cyclone formation to 50%. Interests in the northeast corner of Mexico and far southern Texas should be aware of possible impacts such as heavy rainfall and gusty winds which would arrive by Tuesday.

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

IOH 24 Hr Outlook (0600Z Aug 21)... 0% chance of tropical cyclone formation (south-central Gulf of Mexico near 23.5N-90W)

IOH 48 Hr Outlook (0600Z Aug 22)... 25% chance of tropical cyclone formation (western Gulf of Mexico near 25N-95W

IOH 60 Hr Outlook (1800Z Aug 22)… 50% chance of tropical cyclone formation (just offshore of the Texas/Mexico border near 26N-97W)

IOH 72 Hr Outlook (0600Z Aug 23)... 0% chance of tropical cyclone formation (far southern Texas near 26.5N-99W)

******National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT*****************************

Formation chance through 48 hours...30%

Formation chance through 7 days (168 hours)...50%


AREA OF INTEREST #23... A vigorous and organized tropical wave of low pressure is currently approaching the Republic of Cabo Verde Islands after recently departing the  Western Africa coast. As of 0600Z the center of rotation was near 12.5N-20W… or north of the previous forecast… so the updated forecast below is adjusted accordingly. The westward forecast track has some northward angle overall as the wave of forecast to move toward the surface ridge weakness caused by Area of Interest #21 (Emily). Because the tropical wave has continued to become better organized… and because the regional tropical upper ridge with favorable low shear and upper outflow will persist over the next several days… I have notably raised peak odds of tropical cyclone formation to 70% in this update. Note that regardless of tropical cyclone formation or not… this wave will likely produce heavy rain and gusty winds for the Republic of Cabo Verde Islands beginning later today and into Monday.

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

IOH 24 Hr Outlook (0600Z Aug 21)... 60% chance of tropical cyclone formation (over the southern Republic of Cabo Verde Islands near 15N-23.5W

IOH 48 Hr Outlook (0600Z Aug 22)... 70% chance of tropical cyclone formation (eastern tropical Atlantic near 16.5N-27W)

IOH 72 Hr Outlook (0600Z Aug 23)... 70% chance of tropical cyclone formation (eastern tropical Atlantic near 17.5N-33W)

IOH 96 Hr Outlook (0600Z Aug 24)... 70% chance of tropical cyclone formation (eastern tropical Atlantic near 18.5N-38.5W)

IOH 120 Hr Outlook (0600Z Aug 25)… 70% chance of tropical cyclone formation (eastern tropical Atlantic near 20.5N-42.5W)

******National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT*****************************

Formation chance through 48 hours...10%

Formation chance through 7 days (168 hours)...50%


AREA OF INTEREST #24... A tropical wave of low pressure that has recently crossed the southern Lesser Antilles into the southeastern Caribbean Sea has become considerably better organized with a circular central dense overcast of thunderstorms covering its center of rotation through 0600Z. As a result it appears its odds of tropical cyclone formation is increasing. This system has followed the previous forecast track quite well and the model consensus has converged on the previous track forecast… so the updated one shown below is unchanged. Essentially thru day 5 the forecast track is a reversal of the current westward trajectory to a northeastward one as this system gets pulled toward a sprawling surface ridge weakness consisting of a surface front that moves into the western Atlantic from central Canada combined with area of interest #21 (Emily). From the above notes regarding this system’s organization… I have substantially raised peak odds of tropical cyclone formation to 80%. By 72+ hours some of the upper vorticity currently trapped over the southeast US is forecast to be pushed toward this system by the aforementioned frontal system’s upper trough which will likely result in increased southwesterly shear… and my odds of development are hence lowered from that timeframe.


Regardless of tropical cyclone formation or not... this system will likely produce heavy and potentially flooding rainfall and gusty winds over Haiti… the Dominican Republic… and the southeastern Bahamas by Tuesday and Wednesday. Interests here should be increasingly aware of this system as it’s high chance of tropical cyclone formation also means wind and coastal surf impacts could be stronger.

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

IOH 24 Hr Outlook (0600Z Aug 21)... 80% chance of tropical cyclone formation (eastern Caribbean near 13.7N-67.5W)

IOH 48 Hr Outlook (0600Z Aug 22)... 80% chance of tropical cyclone formation (central Caribbean near 15.2N-71W

IOH 72 Hr Outlook (0600Z Aug 23)... 60% chance of tropical cyclone formation (south-southeast of Haiti near 16.5N-72W)

IOH 96 Hr Outlook (0600Z Aug 24)... 60% chance of tropical cyclone formation (between Haiti and the southeastern Bahamas near 21N-72W)

IOH 120 Hr Outlook (0600Z Aug 25)… 60% chance of tropical cyclone formation (western Atlantic near 24.5N-69.5W)

******National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT*****************************

Formation chance through 48 hours...70%

Formation chance through 7 days (168 hours)...80%


...COMPUTER MODEL SUMMARY... 

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


1200Z (Aug 19) CMC Model Run...

**For tropical depression six... weakens to a remnant low that continues mainly westward into the waters just north of the northern Lesser Antilles by 78 hours... remnant low dissipates near 20N-64W at 96 hours

**For area of interest #21... tropical wave continues west-northwest and then northwest as a tropical low and reaches 26.5N-52.5W at 120 hours

**For area of interest #22... north side of tropical wave organizes into western Gulf of Mexico tropical low just offshore of far southern Texas at 72 hours... soon after the tropical low makes landfall and dissipates inland just west of the Texas/Mexico border at 96 hours.

**For area of interest #23... tropical wave organizes into a tropical low that moves into the eastern Repbublic of Cabo Verde Islands at 42 hours and develops further into a tropical cyclone over the islands at 48 hours... tropical cyclone located at 18.5N-38.5W at 120 hours

**For area of interest #24... tropical wave organizes into a tropical low that crosses the southern Lesser Antilles at 6 hours and reaches the central Caribbean near 14.5N-74.5W at 72 hours... tropical low turns north into Haiti by 96 hours and develops into a tropical depression over the eastern Bahamas by 108 hours... strengthens further into a tropical storm just north of the eastern Bahamas at 120 hours.

**Tropical wave emerges from the west coast of Africa at 132 hours and evolves into a tropical low near 11N-25W at 168 hours


1200Z (Aug 19) ECMWF Model Run...

**For tropical depression six... weakens to a remnant trough near 16N-58W at 42 hours... remnant trough dissipates just east of the northern Lesser Antilles along 60W longitude by 60 hours

**For area of interest #21... tropical cyclone formation suggested near 20N-40.2W at 36 hours... tropical cyclone weakens to a remnant low near 22.5N-45.5W at 72 hours... remannt low curves northward and weakens further to a trough near 30N-49W at 120 hours.  

**For area of interest #22... no development shown

**For area of interest #23... tropical wave organizes into a tropical low that moves into the Republic of Cabo Verde Islands at 42 hours... tropical cyclone formation suggested near 19.2N-34.5W at 90 hours... tropical cyclone reaches 21.5N-38.5W at 120 hours

**For area of interest #24... tropical wave organizes into a tropical low in the central Caribbean near 15N-74W by 72 hours... tropical low lifts northward while degenerating into a surface trough that passes over eastern Cuba by 108 hours... surface trough lifts north into the eastern Bahamas by 120 hours

**Tropical wave emerges from western Africa at 102 hours and organizes into a tropical low that moves into the southern Republic of Cabo Verde Islands by 132 hours... tropical low continues west to 14.8N-33.5W by 168 hours


1800Z (Aug 19) GFS Model Run...

**For tropical depression six... weakens to a remnant trough near 17.5N-56.2W at 30 hours... remnant trough dissipates just east of the northern Lesser Antilles along 59W longitude by 45 hours

**For area of interest #21... tropical cyclone formation suggested near 20N-42.5W at 42 hours... tropical cyclone weakens to a northward-curving remnant low near 21N-46W at 66 hours... north end of broad remnant low re-develops into a tropical cyclone near 29.5N-50W at 108 hours... tropical cyclone located at 30.5N-51W at 120 hours

**For area of interest #22... north side of tropical wave organizes into western Gulf of Mexico tropical low just offshore of the Texas/Mexico border at 66 hours... makes landfall soon thereafter and dissipates inland over the southern Texas/Mexico border at 81 hours.

**For area of interest #23... tropical wave organizes into a tropical low that moves into the Repbublic of Cabo Verde Islands at 39 hours... tropical low develops into a tropical cyclone near 16N-34.5W at 87 hours... tropical cyclone located at 18N-40W at 120 hours.

**For area of interest #24... tropical wave organizes into a southeastern Caribbean tropical low near 12.5N-64.5W at 15 hours... north side of tropical low organizes into a compact tropical cyclone just south of the Dominican Republic at 72 hours... tropical cyclone turns north and crosses over the eastern Dominican Republic at through 90 hours... tropical cyclone passes just east of the eastern Bahamas at 96 hours... tropical cyclone curves northeastward and reaches 23N-68W at 120 hours. 


1800Z (Aug 19) NAVGEM Model Run...

**For tropical depression six... weakens to a remnant trough near 17.5N-56W at 54 hours... remnant trough reverses eastward while tugged by area of interest #21 passing to the northeast and reaches 16N-55W at 120 hours

**For area of interest #21... tropical wave continues west-northwest and then northwest as a tropical low and reaches 26N-54W at 120 hours

**For area of interest #22... north side of tropical wave organizes into western Gulf of Mexico tropical low just offshore of the Texas/Mexico border at 66 hours... makes landfall soon thereafter and dissipates inland over the southern Texas/Mexico border at 96 hours.

**For area of interest #23... tropical wave organizes into a tropical low that moves into the Republic of Cabo Verde Islands at 36 hours... tropical cyclone formation suggested near 16.2N-34W at 78 hours... tropical cyclone located at 18.5N-40.5W at 120 hours

**For area of interest #24... tropical wave organizes into a southeastern Caribbean tropical low near 14N-63W at 12 hours... tropical low continues west-northwest and then northward which takes it into the south coast of the Dominican Republic at 78 hours... tropical low continues north and passes just east of the eastern Bahamas through 96 hours while evolving into a tropical cyclone... tropical cyclone curves northeastward and reaches 23N-67.5W at 120 hours

****Tropical wave emerges from western Africa at 90 hours and organizes into a tropical low that moves into the Republic of Cabo Verde Islands by 126 hours... tropical low continues west to 16.2N-31W at 168 hours


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