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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 #12

*******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 MAY 22 2023 4:30 PM EDT...


Tropical disturbance northeast of the Bahamas has become disorganized in less favorable upper-level winds and is not expected to develop... see area of interest #3 section below for more information. Elsewhere... the GFS and ECMWF models indicate the large-scale eastern North America upper trough that will elongate and transition area of interest #3 into a non-tropical system may become amplified enough to produce another subtropical or tropical disturbance near the southeastern United States coast within the next few days. Therefore will continue regularly scheduled birdseye view posts on this site for another 24 hours (the next post on this site is scheduled for tomorrow afternoon)... should models continue to latch on to an additional subtropical or tropical disturbance birdseye view posts will continue for a few more days on this site.


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 #3 as the first couple were tagged earlier in the year as follows:


Northwest Atlantic cyclonic storm with tropical characteristics during mid-January... the National Hurricane Center (NHC) has recently determined that this storm met the persistence criteria to be considered this season's first (subtropical) storm:


Special report from mid-January on the northwest Atlantic storm... did not classify it as the first area of interest at the time as operationally the NHC suggested it would not meet the persistence criteria to be considered a subtropical or tropical cyclone:


Area of Interest #1... potential for subtropical development in the eastern to central Atlantic in late January:


Area of Interest #2... potential for subtropical development in the northern Gulf of Mexico in early April:


The National Hurricane Center has recently expanded their tropical weather outlook to cover the next 7 days (previous product covered through 5 days). On this site will continue with outlooks not exceeding 5 days (120 hours). On this site I have also begun to list the NHC tropical weather outlook for each area of interest in addition to my outlook for cyclone formation probabilities.


AREA OF INTEREST #3... The tropical disturbance that formed over the weekend to the northeast of the Bahamas... with the support of a passing low-latitude amplified upper trough... has spent today becoming rather disorganized due to a much less favorable upper wind pattern. Specifically the surface low pressure area has become blocked from accelerating eastward due to surface flow around the currently strong Atlantic surface ridge while the parent upper trough/vortex has shifted southeastward into the northeastern Caribbean islands. This now positions the surface low beneath the convergent northwest quadrant of the upper trough/vortex where drier... sinking air is being promoted. Tropical cyclone formation of this feature is therefore not expected.


Going forward... upper divergence will be increasing over the remnants of this disturbance as the next high-latitude upper trough from eastern North America creeps in from the west. However the upper trough will not be amplified... resulting in wind shear unsuitable for tropical development and an elongated area of divergence that transitions the remnants of the disturbance into one or more elongated surface frontal lows passing northwest of Bermuda and offshore of Nova Scotia. As a result expect incliment cloudy and rainy weather for Bermuda to continue over the next 48 hours. Within the two to five day window... the latest runs of the GFS and ECMWF have settled into an interesting pattern regarding the slowly progressing eastern North America upper trough. Specifically the northwestern convergence zone of this trough is expected to usher in a strong surface ridge that dives southeastward across eastern North America from central Canada... with the west side of the surface ridge promoting northward warm air transport and amplification of a warm core upper ridge over central Canada. The adjacent upper ridge amplification results in amplification of the eastern North America upper trough regime... resulting in a reduction in wind shear and increased thundertorm activity (due to stronger upper divergence as the upper trough amplifies) near the southeastern US coast. Although water temps in the region are running 24 deg C... just below the typical 26 deg C needed for tropical development... the upper air support provided by the amplifying upper trough regime may enhance thunderstorm activity needed for tropical development as recent GFS and ECMWF runs suggest. If this trend continues... may have to assign a new area of interest for possible subtropical or tropical activity near the southeastern US coastline in future updates.

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

IOH 24 Hr Outlook (1800Z May 23)... 0% chance of tropical cyclone formation (western Atlantic near 28N-72W)

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

Formation chance through 48 hours...0%

Formation chance through 7 days (168 hours)...0%


...COMPUTER MODEL SUMMARY...

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


1200Z (May 22) CMC Model Run...

**For area of interest #3... surface low becomes weaker and elongated through 42 hours while passing near 29.5N-72.5W... elongating low passes just west of Bermuda through 60 hours... at 78+ hours north end of elongated low becomes a frontal cyclone offshore of Nova Scotia.


0000Z (May 22) ECMWF Model Run...

**For area of interest #3... surface low becomes weaker and elongated through 42 hours while passing near 25.5N-72.5W... elongating low passes just west of Bermuda through 66 hours... at 90+ hours north end of elongated low becomes a frontal cyclone offshore of Nova Scotia.

**Broad frontal low forms offshore of the southeastern US at 120 hours... frontal low acquires possible subtropical characteristics while drifting north onto the southern North Carolina coast through 150 hours.


1200Z (May 22) GFS Model Run...

**For area of interest #3... surface low broader (larger) but still circular thorugh 45 hours while passing near 29.5N-71W... becomes more elongated with multiple centers while passing just west of Bermuda through 63 hours... elongating circulation evolves into multiple frontal lows offshore of the northeastern US and Nova Scotia through 84 hours.

**Large scale upper trough over eastern North America amplifies through 84 hours in response to amplifying central Canada upper ridge... frontal low offshore of the southeastern US and near 30.5N-76.5W forms in response to increased divergence on east side of amplifying upper trough... frontal low evolves into possible subtropical cyclone at 114 hours centered just offshore of South Carolina near 32N-78W... possible subtropical cyclone drifts northwest for landfall on North Carolina/South Carolina border at 129 hours


1200Z (May 22) NAVGEM Model Run... Not available at above-mentioned source

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