*******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 OCTOBER 7 2024 1:01 AM EDT...
The surface and upper air charts valid for October 4 have been added to this post. See birdseye view post #95 (https://www.infohurricanes.com/post/my-2024-atlantic-hurricane-season-birdseye-view-post-95) for the latest information on what is now Hurricane Milton in the southwestern Gulf of Mexico.
…UPDATE… SUNDAY OCTOBER 6 2024 9:09 AM EDT…
The disturbance in the southwestern Gulf of Mexico… tagged as area of interest #34 in this post… became tropical depression fourteen and then Tropical Storm Milton on Saturday. Milton has strengthened further to 60 mph maximum sustained winds through this morning… and some of the models have Milton becoming a strong hurricane as it slides just north of the Yucatan peninsula and toward the Florida Keys and Florida peninsula… interests here need to monitor the progress of Milton. Visit the NHC website hurricanes.gov (hurricanes dot gov) for the latest information on Milton
...FRIDAY OCTOBER 4 2024 3:45 PM EDT...

See Hurricane Kirk and Tropical Storm Leslie sections below for more information on currently active tropical cyclones currently positioned in the open parts of the Atlantic basin. In addition monitoring the following areas of interest:
(1) See area of interest #34 for a complex tropical disturbance which could develop within the next few days in southern Gulf of Mexico and surrounding land areas.
(2) See area of interest #37 section below for an update on the Bermuda-area frontal low which was being monitored for acquisition of tropical characteristics.
(3) In about 2 to 3 days… the major upper trough forecast to recurve Kirk northeastward may produce another surface frontal low or cyclone with tropical characteristics to the south of Newfoundland… toward the 26 deg C warm water around 40N latitude. As such… will add another area of interest for the northwest Atlantic waters in future updates if necessary.
(4) Also watching for possible tropical development from a series of African tropical waves of low pressure following behind Kirk and Leslie... see areas of interest #38 and #39 sections below for more information.
MAJOR HURRICANE KIRK... Over the last couple of days Kirk has been an impressive major hurricane curving northwest across the open central Atlantic. Through late Wednesday the hurricane put on an impressive burst of intensification while quickly forming a sharp eye on satellite pictures... and reached a peak of 125 mph maximum sustained winds. The intensity then dipped to 120 mph maximum sustained winds as of 5 AM EDT Thursday... followed by a second burst of intensification late Thursday through early Friday that vaulted the hurricane into category 4 status with 145 mph maximum sustained winds. As of the most recent 11 AM EDT NHC advisory Kirk has slightly weakened back to 140 mph maximum sustained winds. Satellite pictures show the western outflow of the hurricane has been more constricted relative to the other quadrants of the hurricane due to upper vorticity that has been left behind by the current north Atlantic upper trough... and the dips in intensity on 5 AM EDT Thursday and as of the latest NHC advisory may be due to this. The latest NHC advisory also cites the possibility that an eye wall replacement cycle may be beginning.
The hurricane is curving north while moving into a large-scale mid-ocean ridge weakness induced by the combination of the current north Atlantic frontal cyclone and Bermuda-area frontal low (area of interest #37). Noting my short-term forecast points are nudged north and west compared to my previous... based on Kirk's initial position. A vast area of favorable low shear and upper outflow is setting up as the mid-latitude upper ridge that was in the western Atlantic has recently merged with the expansive tropical upper ridge that Kirk has been under... and the outflow blockage on the west side of the hurricane is likely to drop as the cool-core upper vorticity to the west continues to fade from prolonged isolation from high-latitude cold air in combination with Kirk's thunderstorm latent heat release. However for the 24-hour forecast point I show the same current intensity with the assumption that Kirk dips further in intensity in the next 12 hours due to the possible eye wall replacement cycle ... followed by re-intensification to the current intensity between 12 and 24 hours. By 48 hours the upper vorticity tied to the Bermuda-area frontal low swings east into Kirk and begins to shear it... and so I show weakening through that time. Between 48 and 72 hours Kirk begins to accelerate northeastward on the east side of a strong amplified upper trough that materializes from the merger between (1) the aforementioned shearing upper vorticity that moves it from the Bermuda area... (2) the current north-central US upper trough that enters the Atlantic in 24+ hours while pivoting around the south side of the current central Canada deep-layer cyclone... (3) an eastern fracture of the current central Canada deep-layer cyclone which eventually becomes a high-latitude upper trough positioned between Greenland and Canada. By 72 hours the shear level over Kirk should decrease as the flow on the east side of the strong amplified upper trough is less westerly and more southwesterly which would be more aligned with the track of Kirk... and as the faster forward speed of Kirk is more aligned with the upper southwesterly wind speed... so I expect Kirk to still be a top-end category 1 hurricane by 1200Z October 7. However this is a little lower than my previous intensity forecast for this point as the models are a little faster to accelerate Kirk to the northeast... as such my updated long-range track is adjusted accordingly which places Kirk further into waters less than 26 deg C for 1200Z October 7. Not long after that time Kirk should complete transition into a non-tropical remnant frontal cyclone supported by the eastern divergence zone of the major upper trough. There is some split in the models regarding the forecast track of what will be ex-Kirk... for instance the ECMWF run in the computer model summary section below has ex-Kirk more entangled with the current north Atlantic frontal cyclone which will be toward western Europe by day 4... sending ex-Kirk eastward into Europe sooner. The other extreme is the more western CMC run in the model summary section below which has ex-Kirk whirl into the core of the major upper trough... after which time ex-Kirk drifts east-southeast into the Azores while flung by another frontal low to the east that develops with the support of the eastward-shifting major upper trough. For now my long-range track is similar to the GFS in the model summary section below... which is the middle ground between these two ideas.
Given the current forecast... it appears there is a high likelihood of Kirk's remnant frontal cyclone generating swells that reach the shores of the Azores... Iceland... the British Isles... and the western shores of mainland Europe by next week. Ex-Kirk also has a high chance of producing gusty winds to the British Isles and much of mainland western Europe by next week.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast********
0 Hr Position (1200Z Oct 4)... 140 mph maximum sustained wind major hurricane centered in the central Atlantic at 23N-48.9W
IOH 24 Hr Forecast (1200Z Oct 5)... 140 mph maximum sustained wind major hurricane centered in the central Atlantic at 27.5N-51W
IOH 48 Hr Forecast (1200Z Oct 6)... 115 mph maximum sustained wind major hurricane centered in the central Atlantic at 33N-49W
IOH 72 Hr Forecast (1200Z Oct 7)... 95 mph maximum sustained wind hurricane centered in the north Atlantic at 41N-39W
IOH 96 Hr Forecast (1200Z Oct 8)... Remnant frontal cyclone centered north-northeast of the Azores at 45N-25W
*****National Hurricane Center (hurricanes.gov) official forecast as of 11 AM EDT*************************
5-Day Position (1200Z Oct 9)... 60 mph maximum sustained wind remnant frontal cyclone approaching western Europe while centered at 48N-9W
TROPICAL STORM LESLIE... While in the eastern tropical Atlantic... Leslie has been in a battle with the southern tip of upper vorticity that has been trapped in the mid-latitudes of the eastern Atlantic. Leslie has been strong/tall enough to be held back by the upper vorticity such that it has only been moving very slowly west around the eastern Atlantic surface ridge. Its thunderstorms have appeared blobbed rather than banded in nature... indicating outflow disruption and shear imparted by the upper vorticity. However around 1400Z earlier today the tropical storm appeared better-organized for a short time with more banding in the thunderstorms... and even an eye-type feature... as the southern tip of the upper vorticity has begun to fade as previously forecasted... and accordingly Leslie's intensity was increased to 65 mph maximum sustained winds in the 11 AM EDT NHC advisory. The only thing that hasn't followed the previous forecast is that the southern tip of the upper vorticity was never able to increase the north angle in the west track... and so Leslie is currently south of my previous forecast track.
Over the next 24 hours I expect Leslie to move faster to the west and strengthen as the southern tip of the upper vorticity finishes dissipating. My intensification rate for this time is slower than I showed before as a blob of thunderstorms has covered the eye-type feature since 1400Z... and the thunderstorm blob looks restricted to the north and west... an indication that there is still enough residual upper vorticity disrupting Leslie in the short-term. After 24 hours... Leslie begins interaction with the main body of the aforementioned eastern Atlantic upper vorticity which retrogrades southwest to a position just northwest of Leslie while pushed by the large upper anticyclone that is currently over Kirk. As such the west forward speed around the eastern Atlantic surface ridge is once again slowed... with more north angle introduced in the forecast track. Leslie and the retrograding upper vorticity continue west in tandem through day 5... and combined with the fact that Leslie will reach the southwest side of the eastern Atlantic surface ridge even the surface layer of steering will promote an ongoing north angle in the west track through day 5. The latest model runs are slower to weaken the retrograding upper vorticity which will be fading from isolation from high-latitude cold air... and so my intensification rate in the long range is slower than I previously showed but still ends up briging Leslie into a category 3 major hurricane by day 5. Not long after day 5... it is possible that the northwest/north Atlantic major upper trough that recurves Kirk northeastward deposits some shearing upper vorticity into Leslie's environment... and Leslie could see a round of weakening after the 5-day period.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1200Z Oct 4)... 65 mph maximum sustained wind tropical storm centered in the eastern tropical Atlantic at 10N-33W
IOH 24 Hr Forecast (1200Z Oct 5)... 85 mph maximum sustained wind hurricane centered in the eastern tropical Atlantic at 10.5N-36W
IOH 48 Hr Forecast (1200Z Oct 6)... 65 mph maximum sustained wind tropical storm centered in the eastern tropical Atlantic at 12.5N-37.5W
IOH 72 Hr Forecast (1200Z Oct 7)... 85 mph maximum sustained wind hurricane centered in the eastern tropical Atlantic at 14.5N-40W
IOH 96 Hr Forecast (1200Z Oct 8)... 100 mph maximum sustained wind hurricane centered in the central tropical Atlantic at 17.8N-41.5W
IOH 120 Hr Forecast (1200Z Oct 9)... 120 mph maximum sustained wind major hurricane centered in the central Atlantic at 20.5N-46W
*****National Hurricane Center (hurricanes.gov) official forecast as of 11 AM EDT*************************
5-Day Position (1200Z Oct 7)... 100 mph maximum sustained wind hurricane centered in the central Atlantic at 20.9N-47.7W
AREA OF INTEREST #34... The western Caribbean tropical wave of low pressure that we have been watching over the last few days split into two low-level spins by October 1... one that has been hanging out over the Yucatan peninsula... southeastern Mexico... and surrounding waters... and another in the western Caribbean. Since then the two appear to have slowly merged into a surface trough while cyclonically orbiting each other... however instead of a traditional surface trough axis that is a straight line the surface trough axis appeared to be cyclonically curled with the comma head of the curl over southeastern Mexico and vicinity... with the remainder of the cyclonically curved surface trough axis extending northeastward across the southern Gulf then southeastward into the northwestern Caribbean. The comma head of this complex system did develop into tropical depression eleven-E in the eastern Pacific... positioned just south of southeastern Mexico... from Tuesday to Thursday. Ever since the depression lost its well-defined center... the organization of showers and thunderstorms in the southwestern Gulf of Mexico has improved... and this is likely where the best-defined surface low pressure center for this area of interest will materialize going forward.
What happens to the forecast southwestern Gulf of Mexico tropical low over the next five days largely hinges on cut-off upper vorticity positioned over the south-central US... with this upper-level feature moving rather slowly to the east. It appears for now the region of upper divergence ahead of the upper vorticity will be elongated such that this system is likely to become elongated southwest-to-northeast... possibly while degenerating into multiple centers... while sliding east across the Gulf of Mexico. Wind shear levels imparted by the upper vorticity may be excessive for tropical cyclone formation. Despite these potentially negative factors (shear and possible degeneration into multiple surface centers instead of holding a single center)... the CMC and ECMWF agree on developing this system while sliding it east toward south Florida... and so I do agree with the NHC's recent move in increasing odds of tropical cyclone formation to 50%. Noting by day 3 an upper trough moving across the western US/Canada border region may help to join the central Canada deep-layer cyclone to the south-central US upper vorticity... finally allowing the deep-layer cyclone to kick the upper vorticity and hence this tropical disturbance faster to the east... therefore passage of the tropical disturbance across the Florida peninsula and northwestern Bahamas appears increasingly likely just after the 5-day window.
Regardless of being a single-center tropical cyclone... or vigorous disturbance with multiple surface centers... this disturbance in the days ahead could bring periods heavy rainfall with gusty winds and coastal surf across the Yucatan peninsula... western Cuba... the Florida Keys... the southern and central Florida peninsula... and the northwestern Bahamas.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
Formation chance through 5 days... 50% (eastern Gulf of Mexico near 25.5N-85W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT*************************
Formation chance through 48 hours... 10%
Formation chance through 7 days... 50%
AREA OF INTEREST #37... Satellite image from 0800Z early this morning when the frontal low pressure area near Bermuda had its most organized thunderstorm activity:

The western Atlantic surface frontal low... and overhead supporting upper vorticity that generated the frontal low with this divergence zone... proceeded east-southeast in tandem across the western Atlantic and were proceeding to become vertically stacked just northeast of Bermuda by early today. The vertical stacking resulted in deep-layer cyclonic flow with low shear... and the surface frontal low for a time early this morning had some organized central thunderstorm activity. However since then the thunderstorm activity has dwindled... perhaps due to dry sinking air associated with the western convergence zone of the overhead upper vorticity. Going forward the upper vorticity continues east toward tropical cyclone Kirk… and the deep-layer cyclonic flow on the west side of the upper vorticity and Kirk is forecast to cause this system to dive south then east into the central Atlantic within the next 3 days. Upper convergence on the west side of the upper vorticity… followed by westerly shear induced by the south side of the major upper trough that will be recurving Kirk northeast… make tropical development of this area of interest going forward... and this is my final statement on this area of interest on this blog.
Regarding impact to land areas... most of the weather associated with this system passed northeast of Bermuda instead of overhead.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
Formation chance through 3 days... 0% (central Atlantic near 29N-59W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT*************************
Not in the official outlook
AREA OF INTEREST #38... Satellite imagery shows a tropical wave of low pressure is currently emerging into the eastern tropical Atlantic from the west coast of Africa. Most of the unfavorable upper vorticity in the mid-latitudes of the eastern Atlantic is forecast to retrograde southwest and then west just in front of (west of) Leslie... and a favorable tropical upper ridge (with low shear and outflow) is likely to expand in the wake of this upper vorticity and over this tropical wave. However some of the upper vorticity is also shown being left behind (northeast of) Leslie and toward this tropical wave... and the computer models are not showing this wave developing. This could be due to the trifecta of negative factors including the residual upper vorticity... the dominance of Leslie's surface inflow... and perhaps ingestion of dry Saharan air located just to the north. However in the event Leslie is weaker than currently forecast... this may help give a chance for this tropical wave to develop. Given the list of negative factors... I currently assign a low 10% chance of this tropical wave developing in the next five days.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
Formation chance through 5 days... 10% (eastern tropical Atlantic near 15N-40W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT*************************
Not in the official outlook
AREA OF INTEREST #39... Satellite imagery shows another tropical wave of low pressure is currently moving into western Africa from central Africa... and the NHC had added this as an area of interest into their tropical weather outlook as models are suggesting this wave may develop when it enters the eastern tropical Atlantic by days 4 and 5. This tropical wave will also be dealing with the same potentially negative factors that area of interest (AOI) #38 may be dealing with... minus the dominance of Leslie's surface inflow as this tropical wave will be much farther away from Leslie. Noting the tropical wave is also at a lower latitude (further south) than AOI #38... allowing it to potentially be further away from any residual upper vorticity and dry Saharan air when it enters the Atlantic. And given the model support already materializing for this tropical wave... I have already assigned it higher (30%) odds of development when compared to AOI #38.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
Formation chance through 5 days... 30% (south-southeast of the Republic of Cabo Verde Islands near 11N-22.5W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT*************************
Formation chance through 48 hours... 0%
Formation chance through 7 days... 20%
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
0000Z (Oct 4) CMC Model Run...
**For Major Hurricane Kirk... curves north to 32.5N-49W by 54 hours... then proceeds to make a north-northeast acceleration into the waters midway between Newfoundland and the Azores where it then makes a cyclonic loop around 120 hours while transitioning into a remnant frontal cyclone... the regional upper trough then proceeds to make a new elongated frontal low that heads towards Europe to the east of ex-Kirk which pushes ex-Kirk southeast into the Azores through 156 hours shortly after which time ex-Kirk loses its identity along the cold front of the elongated frontal low.
**For Tropical Storm Leslie... gains hurricane strength and proceeds west-northwest to northwest through 168 hours... reaching 23.5N-53.5W
**For area of interest #34... gradually becomes an SW/NE elongated tropical low in the south-central Gulf of Mexico through 78 hours... the southwestern part of the circulation becomes the dominant while centered just offshore of the northwestern Yucatan by 102 hours... the dominant center continues east-northeast across the southeastern Gulf of Mexico while becoming a tropical cyclone and makes landfall over the far southern Florida peninsula by 150 hours... tropical cyclone continues east into the northwestern Bahamas through 168 hours
**For area of interest #37... dissipates southeast of Bermuda around 54 hours
**For area of interest #38... no development shown
**For area of interest #39... Tropical wave currently moving into western Africa from central Africa proceeds to enter the Atlantic from western Africa around 96 hours... develops into a tropical low SW of the Republic of Cabo Verde Islands around 132 hours... while staying a weak tropical low reaches 15N-35.5W by 168 hours
0000Z (Oct 4) ECMWF Model Run...
**For Major Hurricane Kirk... curves north to 32.5N-49W by 54 hours... through 108 hours accelerates east-northeast while transitioning into a non-tropical frontal cyclone that passes north of the Azores while simultaneously the current north Atlantic frontal cyclone absorbs ex-Isaac and moves into the British Isles... through 138 hours ex-Kirk and the British Isles frontal cyclone proceed to merge over northern France.
**For Tropical Storm Leslie... gains hurricane strength and proceeds west-northwest to northwest through 168 hours... reaching 24N-49W
**For area of interest #34... develops a well-defined center offshore of the northwestern Yucatan peninsula by 90 hours... the center continues east-northeast across the southeastern Gulf of Mexico while becoming a tropical cyclone and makes landfall over the far southern Florida peninsula by 138 hours... while potentially gaining hurricane strength proceeds east-northeast into the waters north of the northwestern Bahamas by 156 hours... subsequently undergoes an east-southeast turn while weakening back to a tropical storm due to wind shear and reaches 28N-75W by 168 hours
**For area of interest #37... dissipates southeast of Bermuda around 54 hours
**For area of interest #38... no development shown
**For area of interest #39... Tropical wave currently moving into western Africa from central Africa proceeds to enter the Atlantic from western Africa around 96 hours... proceeds to undergo rapid tropical cyclone formation SE of the Republic of Cabo Verde Islands around 120 hours... center of the strengthening tropical cyclone passes over the southwestern islands by 138 hours... center reaches 18N-29.5W by 168 hours at hurricane strength
0600Z (Oct 4) GFS Model Run...
**For Major Hurricane Kirk... curves north to 32N-49W by 48 hours... subsequently curves east-northeast while transitioning into a remnant frontal cyclone which passes north of the Azores and moves into western Europe through the British Isles by 135 hours... center of the frontal cyclone proceeds into the Scandinavian region of Europe through 168 hours
**For Tropical Storm Leslie... gains hurricane strength and proceeds west-northwest to northwest through 168 hours... reaching 25N-52.5W
**For area of interest #34... gradually becomes an SW/NE elongated multi-center tropical low across the Gulf of Mexico through 66 hours... northeastern part of the elongated circulation proceeds across Florida and the northwesternmost Bahamas through 108 hours while transitioning into a mutli-center non-tropical frontal low... the remnant frontal low potentially acquires a tropical core of thunderstorms while passing east of Bermuda from 159 to 168 hours... meanwhile the remainder SW portion of this disturbance drifts east and lingers near the northeastern corner of the Yucatan peninsula through 168 hours
**For area of interest #37... dissipates east-southeast of Bermuda around 60 hours
**For area of interest #38... no development shown
**For area of interest #39... no development shown
0600Z (Oct 4) NAVGEM Model Run...
**Not available at above-mentioned source
Comments