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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 #20

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


...UPDATE THURSDAY JUNE 1 2023 3:00 PM EDT...

For the surface low pressure in the northeastern Gulf of Mexico... tagged as area of interest #5 in the full update below... the satellite appearance of the system has continued to improve while it maintains a swirl of clouds with a well-established thunderstorm canopy and warm core anticyclonic outflow in its northern semicircle. This system remains embedded within an upper trough... and based on the above observations it is doing well against the southerly shear being imparted by the trough as the thunderstorm canopy is not displaced too far north of the cloud swirl. A recent ASCAT-B descending satellite scan of surface winds (https://manati.star.nesdis.noaa.gov/ascat_images/cur_25km_METB/zooms/WMBds75.png) showed a well-defined surface circulation with 35 mph maximum sustained winds per the NHC 2 PM EDT tropical weather outlook. The NHC also raised odds of tropical cyclone formation to 70% in the 2 PM outlook which is sensible based on the above observations... and aircraft reconnaissance is scheduled to investigate this system later this afternoon/evening. Using colorized infrared satellite... the thunderstorm canopy has recently weakened in intensity and therefore the negative effects of the overhead upper trough (the current southerly shear... which will soon switch to a northwesterly direction with suppressing upper convergence once the upper trough shifts east) maybe finally affecting this system. Therefore at present I have not elected to issue a special update blog post with a tropical cyclone track and intensity forecast.


Note that any rainfall that occurs across Cuba... the Bahamas... and south Florida in the days ahead will be associated with the eastern divergence zone of the upper trough and not the surface low pressure circulation being monitored in the Gulf of Mexico.


...THURSDAY JUNE 1 2023 4:19 AM EDT...

Surface low pressure area now in the northeastern Gulf of Mexico becoming better organized... and has a chance to become a tropical depression or weak tropical storm in the next 24 hours... and during the first official day of the 2023 Atlantic Hurricane Season... before it later encounters more hostile upper-level wind conditions. Meanwhile the upper trough that generated this feature has potential to bring periods of rainfall to south Florida... Cuba... and the Bahamas through Friday. See area of interest #5 section below for more information.


As done on this site starting last year... I will be sequentially numbering up areas of interest for possible Atlantic tropical development throughout the year... resetting back to #1 at the start of each year. This scheme is so that each area of interest retains a numeric identity from update to update... which reduces confusion when simultaneous areas of interest begin and end when tropical activity increases during the Atlantic Hurricane Season. The current area of interest is tagged #5 as the first four were assigned in earlier birdseye view posts on this site.


AREA OF INTEREST #5... Continuing to monitor a disturbance in the Gulf of Mexico... consisting of a surface low pressure area supported by the eastern divergence zone of an upper trough... for signs of tropical development. To the north and northwest of the disturbance... a warm core blocking upper ridge over eastern North America has been keeping upper trough energy over the western US trapped. In the last 24 hours the blocking ridge has begun to re-amplify and shift westward toward the central US due to ongoing northward warm air transport over the central US... caused by the flow due east of the broad field of low surface pressures over the western US being induced by the divergence zone of the trapped western US energy. The re-amplification of the blocking ridge has in turn caused the Gulf of Mexico upper trough to amplify... reducing the westerly shear and increasing the divergence over the surface low pressure area its supporting. The surface low pressure area has responded positively to this environment while becoming better defined as a cloud swirl featuring nearby thunderstorm activity in its northern semicircle. In some sense this system is behaving as a typical mid-latitude non-tropical system while the surface low pressure area tracked more northward than previously forecast... while cyclonically whirling into the northeastern Gulf of Mexico and toward the axis of the amplifying upper trough... and like a non-tropical system is being aided by the divergence zone of the upper trough. However fully tropical characteristics appear simulatenously present with warm core cirrus outflow clouds streaming northward from the thunderstorm activity and into the southeastern US. Therefore for the short-term this system has a shot at becoming a tropical depression or weak tropical storm... and for this update I have raised my short-term development odds to 40% due to the improved satellite appearance of this system. The models have picked on the change in the forecast track... continuing the theme of similarities to a non-tropical system by having the surface low fully whirl to a position beneath the upper trough axis by 24 hours... followed by the upper trough axis shifting eastward with the surface low drifing southeastward in the northwesterly flow behind the axis beyond the 24 hour mark. The forecast track in my updated outlook below is adjusted toward this latest solution. And like a non-tropical system the surface low will begin its post-mature decay phase while suppressed by the lack of divergence beneath and then west of the upper trough axis. With such a decay phase anticipated... my odds of tropical cyclone formation are dropped to 0% by 48 hours.


Note that the Gulf of Mexico upper trough is forecast to merge with the upper vorticity currently over the eastern US and high-latitude upper trough currently over northeastern Canada expected to dive southeastward. This merger will result in a southwest-northeast tilted upper trough due to the initial position of each of the elements in the merger... with the southeastern divergence zone of the tilted upper trough potentially allowing for additional clusters of thunderstorms and heavy rainfall for Cuba and the Bahamas and perhaps the formation of similar activity over the southern Florida peninsula through Friday. A surface trough of low pressure may also solidify in this region due to the upper divergence regime... however due to the tilt of the upper trough excess westerly shear is expected to suppress opportunity for tropical development. Activity over Cuba and the Bahamas may persist for longer... thru the weekend... as the tilted upper trough will be slow to shift east. Due to the forecast track change noted in the prior paragraph... the surface low in the Gulf of Mexico in the long range is no longer expected to pivot eastward into this activity while instead cyclonically whirling into a position beneath the upper trough axis where it is then forecast to dissipate. In other words any rainfall that develops over south Florida... Cuba... and the Bahamas will NOT be attributed to the surface low in the Gulf of Mexico being monitored for tropical cyclone formation.

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

IOH 24 Hr Outlook (0600Z Jun 2)... 40% chance of tropical cyclone formation (northeastern Gulf of Mexico near 26.5N-86W)

IOH 48 Hr Outlook (0600Z Jun 3)... 0% chance of tropical cyclone formation (eastern Gulf of Mexico near 25N-84.8W)

******National Hurricane Center (hurricanes.gov) official outlook as of 2 AM EDT***************************

Formation chance through 48 hours...20%

Formation chance through 7 days (168 hours)...20%


...COMPUTER MODEL SUMMARY...

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


0000Z (Jun 1) CMC Model Run...

**For area of interest #5... no tropical cyclone formation forecast


1200Z (May 31) ECMWF Model Run...

**For area of interest #5... current northeastern Gulf of Mexico surface low meanders in a cyclonic loop through 42 hours while trapped beneath upper vorticity... surface low dives south-southeast toward the western tip of Cuba through 72 hours as the upper vorticity shifts east which brings the surface low into northerly steering flow on the west side of the upper vorticity... through 84 hours the surface low loses its identity within a surface trough that materializes from western Cuba to the northwestern Bahamas (surface trough generated by the elongated divergence zone on the southeast side of the upper vorticity)


0000Z (Jun 1) GFS Model Run...

**For area of interest #5... current northeastern Gulf of Mexico surface low meanders in a cyclonic loop through 36 hours while trapped beneath upper vorticity... surface low dives south-southeast toward the Yucatan channel (between the Yucatan peninsula and western Cuba) through 78 hours as the upper vorticity shifts east which brings the surface low into northerly steering flow on the west side of the upper vorticity... through 90 hours the surface low loses its identity within a surface trough that materializes on the northwest coast of Cuba (surface trough generated by the elongated divergence zone on the southeast side of the upper vorticity)


0000Z (Jun 1) NAVGEM Model Run...

**For area of interest #5... current northeastern Gulf of Mexico surface low meanders in a cyclonic loop through 30 hours while trapped beneath upper vorticity... surface low dives south-southeast toward the Yucatan channel (between the Yucatan peninsula and western Cuba) through 66 hours as the upper vorticity shifts east which brings the surface low into northerly steering flow on the west side of the upper vorticity... through 84 hours the surface low loses its identity within a surface trough that materializes from western Cuba to the northwestern Bahamas (surface trough generated by the elongated divergence zone on the southeast side of the upper vorticity)

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