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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 #107A (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.*********


...FRIDAY OCTOBER 27 2023 12:22 PM EDT...

The remnant cyclone of Tammy located just east of Bermuda has re-developed enough persistent thunderstorm activity to be re-declared a fully tropical storm as of 11 AM EDT. This special update is to provide a forecast track and intensity for the re-generated tropical storm. Meanwhile... see full update #107 at the link below for more information on other tropical areas of interest being monitored in the Atlantic basin:


TROPICAL STORM TAMMY... Satellite image of Tropical Storm Tammy located just east of Bermuda as of 1510Z:

Despite being over water temps below 26 deg C east of Bermuda... the remnant cyclone of Tammy was able to re-develop a core of thunderstorms due to supportive split flow upper divergence between southwesterlies streaming into a lingering upper trough to the northwest and cut-off upper vortex to the southwest. Although the activity's intensity has waned in recent hours... the NHC by 11 AM EDT deemed that enough activity had persisted to declare the remnant cyclone a re-born tropical storm. My updated forecast track has the same philosophy as the previous from full update #107 but is adjsuted eastward to follow the latest model trends. A faster eastward acceleration for the next 48 hours also makes more sense as Tammy has crept northward to a further north latitude in recent hours... which makes it more likely to couple with the approaching surface ridge weakness associated with the frontal system that will be ejecting from the Great Lakes and eastern Canada. Noting that while Tammy jumps eastward... the lingering upper trough to the northwest will also jump eastward due to the expansion of a warm core deep-layer ridge in the northwest Atlantic to be supported by the warm sector of the aforementioned frontal system. The expanding deep-layer ridge may also induce a south slant to Tammy's eastward track during the 48 hour period. Despite Tammy's now-forecast faster eastward acceleration... the deep-layer ridge is still likely to pin down Tammy such that it falls behind the eastward speed of the upper trough... causing an increase in westerly shear and then exposure to suppressing convergence on the back western side of the upper trough and southeast side of the deep-layer ridge. This hostile upper wind forecast and track which keeps Tammy largely over waters below 26 deg C causes me to forecast degeneration back into a weakening remnant low lacking thunderstorms.


From 48 to 120 hours... the northwest Atlantic deep-layer ridge passes north of Tammy... causing Tammy to shift southward... westward... then northwestward around the south side of the passing ridge. The southward dip in the track places the system back over warmer 26+ deg C waters... and the upper layers of the deep-layer ridge featuring low shear and upper outflow are likely to overspread Tammy's circulation. This is when I forecast Tammy to yet again make a comeback as a tropical cyclone. However I do not show much re-strengthening during this period as by 120 hours the forecast track already lifts Tammy north toward more hostile upper westerly shear associated with the mid-latitude westerlies.


For Bermuda... the worst wind gusts have likely arrived alraedy as Tammy is forecast to reverse eastward and away from the area going forward. Observations (http://www.weather.bm/observations.asp) show gusts have approached tropical storm force (40 mph)... with a recent sustained wind of 26 mph gusting to 39 mph as of 12:55 local time. At around 22:55 local time last evening a sustained wind of 28 mph gusting to 40 mph was logged. Coastal surf will remain a concern for another 24 hours until Tammy makes its forecast acceleration to the east and away.

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

0 Hr Position (1200Z Oct 27)... 65 mph maximum sustained wind tropical storm centered east of Bermuda at 32.2N-61.1W

IOH 24 Hr Forecast (1200Z Oct 28)... 50 mph maximum sustained wind non-tropical remnant low centered east of Bermuda at 32N-60W

IOH 48 Hr Forecast (1200Z Oct 29)... 35 mph maximum sustained wind non-tropical remnant low centered in the central Atlantic at 31.5N-54.5W

IOH 72 Hr Forecast (1200Z Oct 30)... 35 mph maximum sustained wind tropical depression centered in the central Atlantic at 28.5N-53W

IOH 96 Hr Forecast (1200Z Oct 31)... 45 mph maximum sustained wind tropical storm centered in the central Atlantic at 28N-55W

IOH 120 Hr Forecast (1200Z Nov 1)... 45 mph maximum sustained wind tropical storm centered in the central Atlantic at 30N-57.5W

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

5-Day Postion (1200Z Nov 1)... 35 mph maximum sustained wind tropical depression centered in the central Atlantic at 28N-51W

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