*******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 JULY 31 2023 4:30 PM EDT...
See area of interest #17 section below for more information on a tropical low pressure in the open central tropical Atlantic that continues to be monitored for signs of development for the days ahead.
Elsewhere... the tropical low pressure that made landfall at the Florida/Georgia border region on July 28 has since moved back offshore into warm Gulf stream waters offshore of the northeastern United States and is once again being monitored for signs of tropical cyclone formation. See the area of interest #18 section below for more information.
AREA OF INTEREST #17... The tropical low pressure in the open central Atlantic is continuing northwestward in the flow on the southwest side of the Atlantic surface ridge... and will soon curve north and then eventually northeastward into the open north Atlantic as it moves into the surface ridge weakness associated with the cold front currently in the western Atlantic. The tropical low pressure has generally followed the previous forecast track and so the updated track shown below remains the same. Although this feature continues to have thunderstorm activity... over the last 36 hours it remains disorganized and has become displaced to the east thanks to westerly shear being generated by the south side of the current central Atlantic upper vorticity string. After 24 hours the upper-level winds will become more conducive for development as the shearing cool core upper vorticity is forecast to dissipate due to prolonged isolation from high-latitude cold air. Regarding odds of development... I maintain peak odds to 40% instead of going above 50% as it remains to be seen if this disturbance will become too disorganized or not by the short-term westerly shear to be able to develop in the longer-term more favorable upper winds. I drop odds of tropcial cyclone development to 0% by day 4 as this system moves into cooler waters and aligns with the supportive eastern divergence zone of the upper trough currently approaching from eastern Canada... which should transition this system into a non-tropical frontal cyclone supported by the upper trough.
In about three days this system could be passing just offshore of southeastern Newfoundland potentially as a tropical cyclone... surf generated by this system could therfore reach the shores of Newfoundland during that timeframe.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Aug 1)... 30% chance of tropical cyclone formation (central Atlantic near 27N-55W)
IOH 48 Hr Outlook (1200Z Aug 2)... 40% chance of tropical cyclone formation (central Atlantic near 32N-55W)
IOH 72 Hr Outlook (1200Z Aug 3)... 40% chance of tropical cyclone formation (central Atlantic near 38.5N-52W)
IOH 96 Hr Outlook (1200Z Aug 4)... 0% chance of tropical cyclone formation (north Atlanti near 48.5N-44W)
******National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT*****************************
Formation chance through 48 hours...60%
Formation chance through 7 days (168 hours)...70%
AREA OF INTEREST #18... Hovmoller diagram from July 28 to 31 showing the progression of a tropical low pressure that first made landfall over the Florida/Georgia border a couple of days ago... after which time the tropical low moved back offshore from South Carolina and into open northwestern Atlantic waters. The position of the tropical low in each image is circled in yellow:
On July 28th... the center of a tropical low pressure made landfall over the Florida/Georgia border. At the time it was the eighteenth tropical Atlantic area of interest tracked on this site this year. Since then the tropical low curved northward into South Carolina while rounding the western side of the Atlantic surface ridge... followed by a rapid acceleration northeastward into offshore northwestern waters while becoming embedded in the strong flow ahead of a western Atlantic surface cold front and its associated eastern Canada upper trough. Although this tropical low was briefly removed from the NHC TAFB surface analysis on 0000Z July 31... the CIMSS 850 mb vorticity product (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=) confirms the continuity of the mid-level circulation from the July 28th landfall at the Florida/Georgia border region to the current feature now racing northeastward in the northwestern Atlantic. Therefore I am continuing to designate the current northwestern Atlantic feature as the eighteenth area of interest of the year. The National Hurricane Center been mentioning the current northwestern Atlantic feature in their tropical weather outlook since it was offshore of North Carolina yesterday. As of 1200Z earlier today the center of the surface low pressure associated with the feature passed 37N-67W. Indeed this feature has looked increasingly like a tropical system while steadily developing a concentrated mass of thunderstorms with a rotation visible below the cloud deck. However the rotation is also becoming increasingly elongated and less tropical while merging with the incoming western Atlantic cold front... and the NHC as of late has been steadily dropping their odds of tropical cyclone formation for this system. Therefore I assign a 0% chance of tropical cyclone formation and plan this to be my final statement on this system unless it continues to be mentioned in the NHC tropical weather outlook by my next update.
Note that under the supportive eastern divergence zone of the current eastern Canada upper trough... this feature is forecast to strengthen into a non-tropical frontal cyclone offshore of Newfoundland in the next 24 hours... resulting in coastal surf for Newfoundland. Subsequently the remnant frontal cyclone is forecast to accelerate eastward across the north Atlantic while steered around the north side of the Atlantic surface ridge... which will cause it to seperate from the upper trough's supportive eastern divergence zone and hence it will gradually weaken. The weakening remnant frontal low pressure area is projected to move into the British Isles of Europe in about five days.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Aug 1)... 0% chance of tropical cyclone formation (south of southeastern Newfoundland near 44N-54W)
******National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT*****************************
Formation chance through 48 hours...10%
Formation chance through 7 days (168 hours)...10%
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
0000Z (Jul 31) CMC Model Run...
**For area of interest #17... no development shown
**For area of interest #18... transitions into an elongated frontal cyclone near 38.5N-61.5W at 24 hours... the frontal cyclone continues rapidly east across the north Atlantic and moves into the British Isles of Europe by 120 hours.
0000Z (Jul 31) ECMWF Model Run...
**For area of interest #17... develops into a compact tropical depression near 26.5N-55.5W at 36 hours and then a compact tropical storm near 29.5N-56.5W at 54 hours... while passing offshore of Newfoundland transitions into a frontal cyclone at 108 hours... frontal cyclone curves east across the north Atlantic and reaches 47.5N-41W at 120 hours
**For area of interest #18... transitions into an elongated frontal cyclone near 36N-68.5W at 12 hours... while continuing rapidly east across the north Atlantic it gradually weakens to a frontal low that reaches the waters offshore of (southwest of) the British Isles by 120 hours
0600Z (Jul 31) GFS Model Run...
**For area of interest #17... compact tropical cyclone formation suggested near 31.5N-56W at 54 hours... while passing offshore of Newfoundland transitions into a frontal cyclone at 99 hours... frontal cyclone curves east across the north Atlantic and reaches 49N-38W at 120 hours
**For area of interest #18... transitions into an elongated frontal cyclone near 38N-64W at 12 hours... while continuing rapidly east across the north Atlantic it gradually weakens to a frontal low that moves into the British Isles by 120 hours.
0600Z (Jul 31) NAVGEM Model Run...
**For area of interest #17... no development shown
**For area of interest #18... initialized as an elongated frontal low which later strengthens into a frontal cyclone near 40.8N-58W by 24 hours... while continuing rapidly east across the north Atlantic it gradually weakens to a frontal low that reaches the waters just offshore of (just west of) the British Isles by 120 hours
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