*******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.*********
...TUESDAY OCTOBER 22 2024 3:33 PM EDT...
See Remnants of Oscar section below for an update on the former tropical cyclone now departing the eastern and central Bahamas.
For the mid-latitudes of the western Atlantic... the upper vorticity which recently moved offshore from the southeastern United States will soon merge with an upper trough approaching from central Canada... with the merger resulting in an amplified upper trough in the region. By 48 hours the divergence zone of the upper trough will produce a rapidly developing frontal low/cyclone centered just west of Bermuda... with the frontal cyclone continuing north-northeast toward southeastern Newfoundland by 72 hours or so. A surface front will then continue in the western/central Atlantic in the wake of the frontal cyclone afterwards. While the amplified nature of the upper trough may help keep wind shear levels low on its east side... the models are not quiet in agreement that the divergence zone of the upper trough will be focused enough to allow for a well-defined surface low pressure center that can focus thunderstorm activity within the frontal low/cyclone... or along the surface front that lingers in the cyclone's wake. Therefore in this update cycle not declaring a western Atlantic mid-latitude tropical area of interest at this time... however should the situation change will do so in future updates (meanwhile inclement weather and rough seas will occur for Bermuda... Newfoundland... and surrounding waters in the 48 to 72 hour window due to the forecast frontal cyclone... regardless of tropical activity or not).
For the mid-latitudes of the eastern Atlantic... the northwestern Atlantic upper vorticity currently along 52W longitude is forecast to become a cut-off amplified upper trough/vortex in the eastern Atlantic in response to the development of a northeast Atlantic deep-layer ridge (the deep-layer ridge materializes when the current east Canada upper ridge wave becomes stacked over the strong surface ridge currently over the eastern US/western Atlantic... as both ridges shift east). The low shear on the east side of the amplifying upper trough/vortex... combined with a potentially focused upper divergence zone... could trigger a surface tropical disturbance in the open eastern Atlantic in the days ahead... will add an area of interest in the eastern Atlantic in future updates if needed.
For the Caribbean Sea... surface tropical waves of low pressure currently approaching from the central tropical Atlantic have potential to interact with the persisting regional upper ridge/anticyclone which will supply an environment of low shear plus upper outflow that could boost thunderstorms... potentially resulting in a new Caribbean disturbance that may need to be monitored for tropical development in the days ahead.
REMNANTS OF OSCAR... While becoming pulled into the western Atlantic surface ridge weakness (surface pressure falls) generated by the divergence zone of the upper vorticity that recently moves offshore from the southeastern United States... Tropical Storm Oscar made its northeast turn from eastern Cuba and into the eastern and central Bahamas... with the track line more aligned with the NHC and computer model consensus and just northwest of my previous forecast track. However westerly shear imparted by the upper vorticity kept Oscar's thunderstorms and associated gusty winds east of center such that the impacts were felt in the southeastern Bahamas and not the central Bahamas. The shear has taken its toll on Oscar as a recent satellite scan of winds and aircraft recon show that as of 2 PM EDT Oscar has lost its storm strength (maximum sustained winds are now below 40 mph). Moreover the elongated nature of the aforementioned upper divergence zone has caused Oscar to become an elongated surface low without a well-defined center... therefore it no longer qualifies as a tropical cyclone and the 2 PM EDT advisory from the NHC will be the last. This will also be my final statement on Oscar on this blog. Within the next 48 hours the remnant low of Oscar is expected to be absorbed by a frontal low that will develop just west of Bermuda... see the above mid-latitudes discussion for more information on the absorbing frontal low.
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
0000Z (Oct 22) CMC Model Run...
**No tropical development shown in the Atlantic basin through 168 hours (7 days)
0000Z (Oct 22) ECMWF Model Run...
**No tropical development shown in the Atlantic basin through 168 hours (7 days)
1200Z (Oct 22) GFS Model Run...
**Upper vorticity currently in the western Atlantic shifts east with its eastern divergence zone contributing to a surface trough southwest of the Azores at 45 hours... current eastern US/western Atlantic surface evolves into northeast Atlantic deep-layer ridge that pushes the surface trough west-southwest to 30N-40W through 78 hours where it evolves into surface low with possible tropical characteristics... while continuing to move around the deep-layer ridge the surface low moves northwest to 35.5N-45W through 120 hours where tropical cyclone formation suggested... while in flow between deep-layer ridge and approaching upper trough/surface frontal low from Atlantic Canada accelerates north-northeast into cooler waters and loses tropical character... with remnant low fading to a surface trough near 51.5N-32.5W by 162 hours... remnant trough located at 55N-30W at 168 hours
0600Z (Oct 22) NAVGEM Model Run…
**No tropical development shown in the Atlantic basin through 168 hours (7 days)