*******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.*********
...THURSDAY NOVEMBER 23 2023 11:50 PM EDT...
The following two tropical Atlantic areas of interest remain:
(1) A frontal low in the open central Atlantic has moved southeast into waters sufficiently warm for acquisition of tropical characteristics... see area of interest #54 section below for details.
(2) A tropical low pressure spin is now making landfall at the Nicaragua/Costa Rica border region… as such it’s time to develop into a tropical cyclone has ran out… see area of interest #56 section below for details.
AREA OF INTEREST #54... The current central Atlantic frontal low and associated cut-off upper trough have moved southeast into warmer 26 deg C water while pushed by what was a deep-layer ridge in the western Atlantic. The cut-off upper trough has become amplified enough to feature an upper divergence maximum which has allowed the frontal low to develop a well-defined center. As of 1800Z the NHC TAFB surface analysis had the center near 26N-42.5W… and as of 0000Z satellite imagery suggested the center had moved northeast to 26.5N-42W. The combo of warm waters and divergence on the east side of this system’s cut-off upper trough has allowed for a persistent core of showers and thunderstorms just northwest of the surface center… and this system continues to be monitored for signs of acquiring tropical characteristics. Going forward… the cut-off upper trough of this system will be merging with upstream upper troughs currently over eastern Canada and northwestern Atlantic to make a northwest-southeast tilted upper trough that lifts this system northeastward across the eastern Atlantic.
Regarding the forecast track... the long-range model guidance has shifted westward for a track where the center passes just west of the Azores instead of over the islands… the updated forecast below is adjusted based on the initial 0000Z position of this system and the long-range shift in the model guidance. Regarding odds of subtropical cyclone formation... given this system has a better-defined center and nearby thunderstorms I have notably increased short-term odds of subtropical cyclone formation to 60%. By 24 hours the forecast track already brings this system into waters below 26 deg C... and with upper air temps not very cold (200 mb heights above 1200 dekameters) the thermodynamic profile becomes increasingly stable. For this timeframe I pull down odds of subtropical development to a low 20%... with 0% development odds by 48 hours once this system moves into even cooler waters
Regardless of subtropical cyclone formation or not... the east side of this system has potential to spread heavy rains... gusty winds... and coastal surf across the Azores by Sunday.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 12 Hr Outlook (1200Z Nov 24)… 60% chance of subtropical cyclone formation (eastern Atlantic near 27.8N-39W)
IOH 24 Hr Outlook (0000Z Nov 25)… 20% chance of subtropical cyclone formation (eastern Atlantic near 30.5N-37.5W)
IOH 48 Hr Outlook (0000Z Nov 26)… 0% chance of subtropical cyclone formation (eastern Atlantic near 35N-35W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 7 PM EDT***************************
Formation chance through 48 hours... 30%
Formation chance through 7 days... 40%
AREA OF INTEREST #56... The south-central Caribbean tropical low has moved faster to the west-southwest than my previous forecast… under the influence of the current southeastern US surface ridge… and is about to make landfall at the Nicaragua/Costa Rica border. As such time for tropical cyclone formation is running out and this will be my final statement on this area of interest on this blog. Inland pockets of heavy rainfall will be possible across the Nicaragua/Costa Rica border region over the next several hours.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Nov 25)... 0% chance of tropical cyclone formation (western part of Nicaragua/Costa Rica border near 11N-85.2W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 7 PM EDT***************************
Not in the official outlook
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields(http://moe.met.fsu.edu/tcgengifs/).
1200Z (Nov 23) CMC Model Run...
**For area of interest #54... frontal low currently near 26N-42.5W transitions into a possible subtropical cyclone near 27.8N-38.8W at 30 hours… center then accelerates northeast and passes just west of the Azores through 78 hours while transitioning into a non-tropical frontal cyclone… frontal cyclone continues northeast to 47N-23W through 120 hours
**For area of interest #56... no development shown
1200Z (Nov 23) ECMWF Model Run...
**For area of interest #54... frontal low currently near 26N-42.5W accelerates northeast and passes just west of the Azores through 66 hours while strengthening into a non-tropical elongated frontal cyclone… frontal cyclone continues east-northeast to 43N-20W through 120 hours
**For area of interest #56... no development shown
1800Z (Nov 23) GFS Model Run...
**For area of interest #54... frontal low currently near 26N-42.5W transitions into possible subtropical cyclone near 27.5N-40W at 15 hours… transitions back into a more elongated and non-tropical frontal low while located near 29.8N-34W at 36 hours… accelerates northeast and passes just west of the Azores at 69 hours while strengthening into a frontal cyclone… frontal cyclone continues northeast to 46N-22.5W through 120 hours
**For area of interest #56... no development shown
1800Z (Nov 23) NAVGEM Model Run...
**For area of interest #54... frontal low currently near 26N-42.5W accelerates northeast and passes just west of the Azores through 78 hours while strengthening into a non-tropical frontal cyclone… frontal cyclone continues northeast to 47.5N-21W through 120 hours
**For area of interest #56... no development shown