MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #52
*******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.**********
...FRIDAY JULY 16 2021 11:53 PM EDT...
See area of interest #1 section below for an update on the surface low pressure in the open northwest Atlantic that was previously being monitored for tropical development. To the southwest of this surface low…a western Atlantic surface trough has been moving west while steered by the same surface ridge (currently in the central Atlantic) that has also been steering the northwest Atlantic surface low pressure feature. This western Atlantic surface trough formed a couple of days ago in the eastern divergence zone of the current upper vorticity string that covers the Caribbean and western Atlantic. Along this surface trough and earlier this afternoon…26.5N-73W…there appeared to be a spin with some organized shower activity developing while supported by upper divergence between the aforementioned upper vorticity string and another upper vortex currently located offshore of the southeast US. This feature has since lost shower activity while moving west directly into the upper vortex where there is a lack of upper divergence…and tropical development here is not expected.
Elsewhere…tropical development in the Atlantic basin has been suppressed by a low-latitude (southern located) upper vorticity string toward the west side of the basin (mentioned in the previous paragraph) and dry Saharan air toward the east side of the basin. However some recent model runs suggest in about four days a strong tropical wave of low pressure from Western Africa will emerge into the eastern tropical Atlantic. The current configuration of the Madden Julian Oscillation (MJO) has favored suppressed thunderstorm activity in the Atlantic tropics since July started (https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml). While the recent upheaval of activity in the eastern Pacific suggests the favorable phase of the MJO might finally be shifting back east toward the Atlantic…the favorable MJO pulse may not make it east all the way to the forecast tropical wave…and none of today’s model runs develop the wave after it enters the Atlantic…perhaps as the wave is also forecast to exit Africa a little further to the north where it may ingest dry Saharan air. Therefore for now… I have not declared a new area of interest for the forecast tropical wave.
AREA OF INTEREST #1…Using zoomed-in satellite imagery of the northwest Atlantic surface low pressure area (available at https://www.tropicaltidbits.com/storminfo/)...the center is currently located at 41.5N-54W with an east-northeast heading while on the northwest side of the steering surface ridge. Although the surface low remains supported by the eastern divergence zone of incoming upper vorticity to the west…thunderstorm activity near the center has come to an end as it tracks into cooler water…and combined with ongoing northwesterly shear keeping any of the remaining thunderstorm activity well to the southeast of the center…the window for tropical development has closed. As such…this is my final statement on this system on this blog.
******infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Jul 18)…0% chance of tropical cyclone formation (north Atlantic near 43N-47.5W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z CMC Model Run...
**For area of interest #1...surface low weakens to a surface trough near 42.5N-54W at 18 hours.
**Strong tropical wave forecast to emerge from Western Africa at 48 hours…forms a surface low near 10N-21W at 60 hours…surface low located at 10.5N-27W at 120 hours.
1200Z ECMWF Model Run...
**For area of interest #1…surface low weakens to a surface trough near 42.5N-54W at 24 hours.
**Large and strong tropical wave forecast to emerge from Western Africa to the northeast of the Republic of Cabo Verde Islands at 96 hours…wave loses low pressure spin at 144 hours near 36W longitude.
1800Z GFS Model Run...
**For area of interest #1...surface low weakens to a surface trough near 41.5N-55W at 9 hours.
**Large and strong tropical wave forecast to emerge from Western Africa at 96 hours…low pressure spin of tropical wave located at 8.5N-32W at 120 hours…wave loses low pressure spin at 126 hours near 34W longitude.
1800Z NAVGEM Model Run...
**For area of interest #1...initialized as a weakening surface trough…no tropical development shown.
**Large and strong tropical wave forecast to emerge from Western Africa at 96 hours…wave loses low pressure spin at 126 hours near 36.5W longitude.