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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 #27A (Special Update)

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


...MONDAY JUNE 19 2023 8:30 PM EDT...

The following is a special update on recent tropical activity in the Atlantic as I am currently on vacation. We have had a surprising and unseasonably early mid-June upheaval in activity under the following upper air pattern:


(1) From June 10 to 17 the upper vorticity that was over eastern North America and western Atlantic shifted eastward to the northeast corner of the Atlantic while leaving behind some lower-latitude upper vorticity in the central Atlantic. At the same time upper vorticity from the western US and central Canada teamed up to make the latest round of upper vorticity now over the western Atlantic.


(2) The latest rounds of upper vorticity over the northeast and western Atlantic are not reaching as far south as seen previously… allowing for expanding tropical upper ridge cells over the southern Caribbean and eastern tropical Atlantic. The lower-latitude central Atlantic upper vorticity over the last couple of days (June 17 to 19) has retrograded westward  while pushed around a warm core high-latitude upper ridge cell supported by the warm sector of the latest west Atlantic frontal systems… allowing for westward expansion of the eastern Atlantic tropical upper ridge cell


(3) The outflow of the eastern Atlantic tropical upper ridge cell has enhanced the thunderstorms and development of a pair of tropical waves of low pressure that have departed from Africa over the last several days which is a pattern unusual for June and typical for later in the season… each wave is now being monitored by the National Hurricane Center for possible tropical cyclone formation as the global models have most favored development in this region since June 15. See area of interest #7 and #8 sections below for more information.


(4) Intermittent runs of the CMC and GFS models have also hinted at a western development mode more typical for June… either underneath the expanding south Caribbean upper cell or along the latest western Atlantic frontal boundary in between Bermuda and the southeast US coast. Over the last several days the southern Caribbean has indeed seen rounds of increased thunderstorm activity caused by the outflow of the south Caribbean upper ridge cell in combination with a pair of surface tropical waves of low pressure that have recently passed through the area and into Central America. So far there are no signs of a concentrated circular low-level spin in the southern Caribbean or along the west Atlantic frontal boundary (per the CIMSS 850 mb vorticity product) to declare another area of interest (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=)


Note my forecasts and outlooks below were generated at 0600Z earlier today… however I could not publish until now due to my ongoing vacation. While on vacation I will continue to issue special updates on active disturbances or tropical cyclones when possible... meanwhile refer to the National Hurricane Center website hurricanes.gov (hurricanes dot gov) for up to the minute latest information on the Atlantic tropics.


Hovmoller diagram of the Atlantic tropical belt from June 13 to 18 showing the progression of areas of interest #7 and #8 to the east encircled in yellow and Caribbean thunderstorm activity to the west encircled in red:


Satellite image as of 1200Z June 19 showing areas of interest #7 and #8 along with a simplified surface analysis of surface low pressures (Ls)… high pressure ridges (Hs)… and fronts (red lines) based on the NHC TAFB surface analysis at the time:


AREA OF INTEREST #7 (RECENTLY UPGRADED TO TROPICAL STORM BRET)… A tropical wave of low pressure that emerged from the west coast of Africa on June 15 was immediately introduced into the NHC tropical weather outlook to be monitored for

tropical cyclone formation. This was due to computer models picking up on its development potential in the low shear and upper outflow environment of the recently expanding eastern tropical Atlantic upper ridge cell. The tropical wave was accompanied by this season’s first notable dry Saharan air surge which did not allow it to produce consistent thunderstorm activity… and by June 17 it was also competing for surface inflow and upper outflow with another adjacent strong tropical wave to to the east… more on the adjacent wave is in the area of interest (AOI) #8 section below. As of 11 AM EDT today the tropical wave has overcome these difficulties and has now strengthened to the third cyclone of the 2023 Atlantic Hurricane Season… tropical depression three. As of 5 PM EDT the depression was upgraded to Tropical Storm Bret with 40 mph maximum sustained winds.


My westward track forecast below is based on a typical 5W longitude per day progression for this region of the Atlantic… which was also confirmed by the above Hovmoller diagram. Intensity-wise I project this system to become a moderate to strong tropical storm through 48 hours… after which time some northerly shear from the east side of the Caribbean upper ridge cell and southwest side of the low-latitude central Atlantic upper vorticity will likely begin to negatively affect this system (the low-latitude central Atlantic upper vorticity will stop retrograding westward and away while merging with the current western Atlantic upper vorticity). By 96 to 120 hours the northward warm air transport ahead of the current eastern US frontal system will have amplified the Caribbean upper ridge cell… with this cell causing a chunk of the central Atlantic upper vorticity to retrograde southwest into the Lesser Antilles and just out ahead of this system. I forecast weakening of this system during this timeframe due to a short-lived burst of westerly shear from the retrograding upper vorticity chunk… but not a total collapse of this system as the shear then relaxes by switching to a less severe southerly vector not totally opposed to the forward track of this system as the upper vorticity chunk continues its westward and away retrogression. I also bend the forecast track northward in the 96 to 120 hour window as this system will likely be strong/tall enough to be pulled by the aforementioned upper vorticity chunk.


Interests in the central and northern Lesser Antilles should be aware of this system as it will likely bring periods of heavy rainfall… coastal surf… and gusty winds in about 5 days from now. Impacts may be stronger if Bret manages to strengthen more than currently forecast… for example if future upper wind forecasts lean more favorable for Bret… keep in touch with up to the minute latest forecasts by visiting the NHC site (hurricanes.gov).

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

0 Hr Position (0600Z Jun 19)… Tropical low centered at 10.5N-37.5W

IOH 24 Hr Forecast (0600Z Jun 20)… 45 mph maximum sustained wind tropical storm centered at 11N-42.5W

IOH 48 Hr Forecast (0600Z Jun 21)… 60 mph maximum sustained wind tropical storm centered at 12N-47.5W

IOH 72 Hr Forecast (0600Z Jun 22)… 60 mph maximum sustained wind tropical storm centered at 13N-52.5W

IOH 96 Hr Forecast (0600Z Jun 23)… 60 mph maximum sustained wind tropical storm centered just east of the Lesser Antilles at 14N-57.5W

IOH 120 Hr Forecast (0600Z Jun 24)… 50 mph maximum sustained wind tropical storm centered just east of the northern Lesser Antilles at 16N-60W

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

Peak strength (0600Z Jun 22)… 80 mph maximum sustained wind hurricane centered at 13.7N-55.5W

5-Day Position (1800Z Jun 24)… 70 mph maximum sustained wind tropical storm centered southwest of Puerto Rico at 17N-68.5W


AREA OF INTEREST #8… To the east of AOI #7… recently upgraded to Tropical Storm Bret… an additional strong tropical wave of low pressure emerged from the west coast of Africa on June 17 and proceeded to become better organized on the evening of June 18. As a result of these observations and some model support from the CMC and GFS… this wave was upgraded to another area of interest as of today. For the outlook below… I start with low odds of tropical cyclone formation and ramp them up with time as I do not anticipate any immediate development due to the current lack of concentrated low-level spin in the CIMSS 850 mb vorticity product and as the thunderstorm activity is not very well organized. Due to likely competition with Tropical Storm Bret which is further along in its development and thus will likely dominate the region… I cap my peak odds of tropical cyclone formation at a level below the NHC outlook as of this writing.


Noting that the current western and central Atlantic upper vorticity will merge and create a surface ridge weakness with the combined eastern divergence zones… the forward speed in my outlook below is slowed in response to this weakness in the 72 to 96 hour window. Later the current Caribbean upper ridge cell is forecast to amplify which will tilt the upper vorticity into a southwest-northeast configuration… with the northwestern convergence zone of the tilted vorticity helping to recover the Atlantic surface ridge. As a result I return to a faster forward speed in the 96 to 120 hour window.

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

IOH 24 Hr Outlook (0600Z Jun 20)… 0% chance of tropical cyclone formation (eastern tropical Atlantic near 9N-32W)

IOH 48 Hr Outlook (0600Z Jun 21)… 20% chance of tropical cyclone formation (eastern tropical Atlantic near 10N-37W)

IOH 72 Hr Outlook (0600Z Jun 22)… 30% chance of tropical cyclone formation (central tropical Atlantic near 10.5N-41W)

IOH 96 Hr Outlook (0600Z Jun 23)… 30% chance of tropical cyclone formation (central tropical Atlantic near 11.5N-45W)

IOH 120 Hr Outlook (0600Z Jun 24)… 30% chance of tropical cyclone formation (central tropical Atlantic near 12.5N-50W)

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

Formation chance through 48 hours...50%

Formation chance through 7 days (168 hours)...60%


...COMPUTER MODEL SUMMARY...

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


CMC Model…

**0000Z (Jun 19)… Area of interest #7 passes over central Lesser Antilles as a tropical low at 96 hours after which time it crosses the Caribbean as a tropical wave… Area of Interest #8 not shown to develop

**1200Z (Jun 18)… Area of interest #7 not shown to develop… Area of Interest #8 forecast to develop into possible tropical depression near 40W longitude by 120 hours after which time it curves northwest while weakening

**0000Z (Jun 17)… Area of interest #7 not shown to develop… Area of interest #8 shown to develop between 40W and 50W longitude thru 168 hours

**0000Z (Jun 16)… Areas of interest #7 and #8 not shown to develop… short-lived and northeast-moving tropical cyclone ahead of a cold front passes west of Bermuda between 60 and 102 hours

**0000Z (Jun 15)… Areas of interest #7 and #8 not shown to develop

**0000Z (Jun 14)… Area of interest #7 and #8 not shown to develop


ECMWF Model…

**1200Z (Jun 18)… Area of interest #7 forecast to be a tropical storm near 55W longitude at 84 hours after which time it crosses the Lesser Antilles while weakening to a tropical wave… Area of interest #8 not shown to develop

**0000Z (Jun 17)… Area of interest #7 forecast to be a compact hurricane east of the Lesser Antilles islands at 120 hours… weakens to a remnant low over the northern islands and NE Caribbean through 168 hours… Area of interest #8 not shown to develop

**1200Z (Jun 16)… Area of interest #7 forecast to be a hurricane east of the northern Lesser Antilles at 168 hours… Area of interest #8 not shown to develop

**0000Z (Jun 16)… Area of interest #7 forecast to be a hurricane east of the northern Lesser Antilles at 168 hours… Area of interest #8 not shown to develop

**0000Z (Jun 15)… Area of interest #7 forecast to be a tropical storm east of the Lesser Antilles islands at 168 hours… Area of interest #8 not shown to develop


GFS Model...

**0000Z (Jun 19)… Areas of interest #7 and #8 forecast to be competing compact tropical storms to the east-northeast of the Lesser Antilles by 144 hours… by 168 hours AOI #7 becomes the dominant while passing north of the Lesser Antilles… Caribbean tropical low suggested north of Honduras at 81 hours after which time no development shown as it weakens to a trough passing over the Yucatan peninsula and western Gulf of Mexico

**1200Z (Jun 18)… Area of interest #7 forecast to be a hurricane well northeast of the Lesser Antilles at 144 hours with a northward curvature to 25.5N-57.5W through 168 hours… Area of interest #8 shown to develop into a tropical low near 34W longitude by 84 hours after which time it weakens back to a wave near 40W longitude through 120 hours… Caribbean surface trough suggested offshore of Nicaragua and Honduras by 84 hours which evolves into a compact tropical storm that passes west of Cayman Islands at 96 hours then over western Cuba at 105 hours and then weakens to a tropical depression while moving into the northern Florida peninsula through 144 hours

**0600Z (Jun 17)… Area of interest #7 forecast to be a hurricane well northeast of the Lesser Antilles at 168 hours… Area of interest #8 not shown to develop

**1200Z (Jun 16)… Area of interest #7 forecast to be a hurricane northeast of the Lesser Antilles at 168 hours… Area of interest #8 not shown to develop

**0000Z (Jun 16)… Area of interest #7 forecast to be a tropical storm between 40W and 45W longitude through 102 hours and weakens to a remnant low east of the northern Lesser Antilles through 168 hours… Area of interest #8 not shown to develop… western Caribbean tropical storm suggested north of Honduras at 102 hours which subsequently drifts north and dissipates south of the western tip of Cuba through 144 hours

**1200Z (Jun 15)… Area of interest #7 forecast to be a tropical storm between 35W and 40W longitude through 90 hours and weakens to a remnant low east of the Lesser Antilles through 168 hours… Area of interest #8 not shown to develop… western Caribbean tropical storm suggested north of Honduras at 120 hours which crosses western Cuba… south Florida… and into the waters offshore of the southeastern US through 168 hours


NAVGEM Model…

**0000Z (Jun 19)… Area of interest #7 forecast to be a large and intense hurricane over the northern Lesser Antilles at 126 hours which moves across the northeast Caribbean and toward the Dominican Republic through 168 hours… Area of interest #8 not shown to develop

**1200Z (Jun 18)… Area of interest #7 forecast to be a large and intense hurricane over the northern Lesser Antilles at 144 hours which moves into the Virgin Islands at 168 hours… Area of interest #8 not shown to develop

**0600Z (Jun 17)…Area of interest #7 forecast to be a large and intense hurricane over the northern Lesser Antilles at 168 hours… Area of interest #8 not shown to develop

**1200Z (Jun 16)…Area of interest #7 forecast to be a large tropical storm between 45W and 50W longitude at 168 hours… surface front decays into a possible tropical disturbance offshore of the Carolinas through 168 hours… Area of interest #8 not shown to develop

**0000Z (Jun 16)…Area of interest #7 and #8 not shown to develop

**1200Z (Jun 15)…Area of interest #7 and #8 not shown to develop

**0000Z (Jun 15)…Area of interest #7 forecast to be a broad tropical low between 35W and 40W longitude at 168 hours… Area of interest #8 not shown to develop… broad western Caribbean tropical low suggested just after 168 hours

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