*******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.*********
…UPDATE…MONDAY SEPTEMBER 23 2024 6:40 PM EDT…
For ex-Gordon… tagged as area of interest #29 on this blog post… over the late part of the weekend and into today the remnant low began its northward acceleration around the west side of the surface layer of the regional steering deep-layer ridge sooner… bringing ex-Gordon into shearing upper westerlies on the north side of the ridge sooner such that it is no longer an area of interest for tropical redevelopment. As such it will not be mentioned as an area of interest in future updates.
...SATURDAY SEPTEMBER 21 2024 10:53 PM EDT...
The following are special updates on current areas of interest in the Atlantic basin while on vacation. I completed the forecasts for area of interest #29 through #31 at 1200Z earlier today… and the forecast for area of interest #32 at 1800Z earlier today… however the situation for each area of interest has not changed since then. Note area of interest #30 is likely bring impacts to Honduras… Belize… the Yucatan region of Mexico… western Cuba… and south Florida over the next five days regardless of tropical cyclone formation or not… see area of interest #30 section for more details.
Satellite image of the Atlantic basin as of 1520Z… current areas of interest are highlighted with their numeric identity:
Surface chart of the Atlantic basin as of 0600Z… current areas of interest are highlighted with their numeric identity:
Upper air chart of the Atlantic basin as of 0600Z… current areas of interest are highlighted with their numeric identity:
AREA OF INTEREST #29 (REMNANTS OF GORDON)... In the open central Atlantic... the remnant low pressure swirl of what was tropical cyclone Gordon has seen its thunderstorms increasingly stripped away by wind shear induced by an overhead band of upper vorticity. Eventually wind shear is expected to relax… coupled with an increase in upper outflow… as the upper vorticity band fades from prolonged isolation from high-latitude cold air which allows the currently developing deep-layer ridge to the north to take over… this is why ex-Gordon continues to be monitored for signs of redevelopment. The deep-layer ridge will be shifting east during the forecast period while getting pushed by the current northwest Atlantic frontal low and its upper vorticity... with ex-Gordon rounding the west side of the eastward-shifting ridge such that it tracks northwest… north… then northeast. My updated forecast track is nudged south over the previous as ex-Gordon has not begun to move northwest yet. I have lowered my peak odds of tropical cyclone formation to 10% as the swirl of ex-Gordon remains void of thunderstorm activity… which indicates the upper-layer of the developing deep-layer ridge has not yet developed into an outflow-enhancing anticyclone… and by the time it does ex-Gordon will now have a narrower window of time to take advantage of the outflow before moving into cooler waters. By 72 hours ex-Gordon moves into cooler waters... and will be near a surface front linking the approaching northwest Atlantic frontal low to the current deep-layer North Atlantic cyclone. Although the southward-nudged track forecast may mean ex-Gordon is just south of the front instead of already merging with it… the cooler waters are enough for me to end the outlook by 72 hours while pulling tropical development odds back down to 0%.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Sep 22)... 0% chance of tropical cyclone formation (central Atlantic near 27.5N-44W)
IOH 48 Hr Outlook (1200Z Sep 23)... 10% chance of tropical cyclone formation (central Atlantic near 31N-45W)
IOH 72 Hr Outlook (1200Z Sep 24)... 0% chance of tropical cyclone formation (central Atlantic near 35N-41W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT*************************
Formation chance through 48 hours... 0%
Formation chance through 7 days... 0%
Removed from NHC Outlook as of 8 PM EDT
AREA OF INTEREST #30... An axis of upper vorticity extends from the northwestern Atlantic to the east coast of the Yucatan peninsula… and divergence on the east side of this feature has contributed to concentrated Caribbean thunderstorms offshore of Nicaragua and Honduras. Caribbean tropical cyclone formation is not expected in the next 24 hours due to wind shear also induced by the upper vorticity. After that time wind shear begins to relax due to the following upper-level wind evolution... (1) the Mexico warm core upper ridge continues to amplify across the eastern United States due to warm southerly flow ahead of a series of forecast central North America frontal lows... (2) The upper ridge pushes the upper vorticity over the Yucatan westward and away into the southwestern Gulf of Mexico... (3) the remainder of the upper vorticity in the northwest Atlantic continues east and away… (4) a shear-reducing and outflow enhancing upper anticyclone develops and expands over this disturbance and in between the two pieces of departing upper vorticity. I currently forecast whatever western Caribbean surface low pressure field that develops to move slowly west toward Belize or the southeast coast of Mexico's Yucatan peninsula while pushed by the weak steering provided by the narrow east US coast surface ridge that will be supported by the eastern convergence zone of the eastern US upper ridge. After landfall with Belize and the Yucatan... in 3+ days I currently expect a north then northeast turn toward the southern or southeastern Gulf of Mexico while this system edges toward the ridge weakness associated with one of the forecast central North America frontal lows that moves into the Great Lakes. Noting that by day 5 some of the latest model data shows the upper vorticity over the SW Gulf of Mexico team up with the upper trough that moves into the Great Lakes… potentially displacing the upper anticyclone over this disturbance southeastward which would allow upper southwesterly flow between the anticyclone and upper vorticity to overspread this disturbance. The upper southwesterly flow may also help add an east tilt to the longer-term track. For the next five days... I assign a low 20% peak odds of tropical cyclone formation as the models tend to develop this system when its in the Gulf beyond day 5. My low odds of development are also a reflection of the land interaction with Belize and the Yucatan along my current track forecast... and I dip the odds back to 0% on days 4 and 5 when this system is most likely to be inland. However note that in future updates the 5-day position will likely be over Gulf of Mexico waters and so I expect to issue higher long term odds of development for this area of interest in future updates. I recommend interests along the Caribbean coasts of Honduras... Belize... and the Yucatan to monitor the progress of this area of interest... for possible tropical cyclone impacts (gusty winds and coastal surf) after this weekend. This system may also bring prolonged periods of heavy rainfall with flash flooding potential to coastal and inland areas as well. The aforementioned day-5 upper southwesterly flow may also spread the heavy rainfall across western Cuba and south Florida by late this upcoming week.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Sep 22)... 0% chance of tropical cyclone formation (northeast coast of Honduras near 16N-84.5W)
IOH 48 Hr Outlook (1200Z Sep 23)... 10% chance of tropical cyclone formation (just offshore of north-central Honduras near 16.2N-85.8W)
IOH 72 Hr Outlook (1200Z Sep 24)... 20% chance of tropical cyclone formation (just offshore of Belize near 17N-87.5W)
IOH 96 Hr Outlook (1200Z Sep 25)... 0% chance of tropical cyclone formation (inland Belize/ Guatemala/ Mexico border intersection near 17.5N-89.1W)
IOH 120 Hr Outlook (1200Z Sep 26)… 0% chance of tropical cyclone formation (northeastern Yucatan peninsula near 20.5N-88W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT*************************
Formation chance through 48 hours... 0%
Formation chance through 7 days... 70%
AREA OF INTEREST #31... The surface low currently near 25N-55W has been quasi-stationary while in conflicting steering between ex-Gordon (area of interest #29) to the east and current northwestern Atlantic frontal low. After 24 hours the northwest Atlantic frontal low dives southeast toward this area of interest... causing this area of interest to lift north… northwest… then southwest while pulled into the north side of the frontal low where it will likely be absorbed by the frontal low by day 5. Regarding odds of tropical cyclone formation... I have increased my peak odds to 50% as thunderstorm activity has increased just northeast of the center while the regional upper vorticity that was shearing it is drifting west and away under the influence of the developing deep-layer ridge to the north. On days 4 to 5 the odds are then tapered down to 0% as this system whirls into the north and northwest quadrants of the aforementioned frontal low… where the upper vorticity stacked over the frontal low will be producing suppressive convergence that should weaken this system and hence increase the odds it becomes absorbed by the frontal low.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Sep 22)... 50% chance of tropical cyclone formation (central Atlantic near 25N-55W)
IOH 48 Hr Outlook (1200Z Sep 23)... 50% chance of tropical cyclone formation (central Atlantic near 27.5N-55W)
IOH 72 Hr Outlook (1200Z Sep 24)... 40% chance of tropical cyclone formation (central Atlantic near 32N-55W)
IOH 96 Hr Outlook (1200Z Sep 25)... 10% chance of tropical cyclone formation (northeast of Bermuda near 35N-60W)
IOH 120 Hr Outlook (1200Z Sep 26)... 0% chance of tropical cyclone formation (just northeast of Bermuda near 32.5N-62W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT*************************
Formation chance through 48 hours... 10%
Formation chance through 7 days... 10%
AREA OF INTEREST #32… Satellite imagery is picking up on a tropical wave of low pressure approaching the west coast of Africa… featuring a distinct area of thunderstorms. Computer models over the last few days have suggested this wave may develop as it continues west across the eastern tropical Atlantic… and it has been added into the NHC tropical weather outlook. The steering feature that will push this wave west over the next five days will be the same deep-layer ridge that steers ex-Gordon (area of interest #29) … once that ridge shifts east into the mid-latitudes of the eastern Atlantic. The atmospheric setup favors tropical development with an ongoing tropical upper ridge axis featuring low shear and upper outflow… however currently assigning a low 30% peak odds of tropical cyclone formation for the next five days… and not higher… as tropical waves in this region of the Atlantic have had a history of underperforming over the last several weeks. However should the wave show signs of organized thunderstorm activity in the future… will later increase odds of development in later updates.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
Formation chance through 5 days... 30% (eastern tropical Atlantic near 15N-38W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT*************************
Formation chance through 48 hours... 0%
Formation chance through 7 days... 40%
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