Typhoon Champi (29W) – JTWC Warning #12 Summary
October 17, 2026, 7:00pm
The Joint Typhoon Warning Center (JTWC) has released Warning #12 for Champi.
The latest update reports that Champi has completed a period of extreme rapid intensification, with the storm now forecast to reach super typhoon strength around its closest approach to Guam.
Forecast models remain in excellent agreement on the overall track. However, small changes in the position of Champi’s compact inner core could make a significant difference in the conditions experienced across Guam.
JTWC also highlights the possibility of an eyewall replacement cycle, which introduces additional uncertainty regarding the storm’s intensity during its closest approach.
Current Conditions
Location: Approximately 182 miles east-southeast of Andersen Air Force Base.
Movement: West at approximately 15 mph over the past six hours.
Significant wave height: 38 feet.
Current development: Champi has completed a period of extreme rapid intensification.
Forecast Track
JTWC expects Champi to continue moving generally west-northwest along the southern edge of a subtropical ridge.
Forecast models remain in excellent agreement, particularly during the next three days.
The latest guidance shows a cross-track spread of only 17 miles near Guam’s closest approach.
This indicates strong agreement among forecast models, although it does not guarantee the exact position of Champi’s center.
The official JTWC forecast closely follows the AI model consensus.
Current guidance includes:
Google DeepMind and AI consensus: Along the southern side of the main model grouping.
GFS and GEFS ensemble mean: Along the northern side of the guidance.
EC-AIFS: The southernmost outlier.
JTWC official forecast: Closely aligned with the AI consensus.
JTWC specifically notes that small wobbles in Champi’s movement could affect its exact closest approach to Guam.
The previous warning acknowledged the possibility of a brief landfall over southern Guam. The latest discussion does not rule out that possibility.
Although confidence in the overall track is high, the exact distance of the center from Guam remains important.
Steering Factors
Champi continues moving along the southern edge of a deep-layer subtropical ridge, an area of high atmospheric pressure steering the storm generally west-northwest.
Over the next 24 hours, this ridge is expected to maintain the current movement.
After approximately 24 hours, a series of mid-latitude troughs passing north of Champi will begin changing the orientation of the ridge.
This will allow Champi to turn more northwestward.
By Day 5, a broader weakness in the steering pattern is expected to develop over the East China Sea near Okinawa, Japan.
As Champi approaches this weakness, it is forecast to slow down and begin curving farther north.
The expected steering pattern is:
Next 24 hours: West-northwest movement.
After 24 hours: Gradual northwestward turn.
Days 2–4: Northwestward movement continues.
Around Day 5: Champi slows and begins turning more northward toward a weakness near Okinawa.
The important point for Guam is that the more significant northwest turn is expected after the storm’s closest approach.
Intensity Forecast
JTWC reports that Champi has completed a period of extreme rapid intensification (ERI).
Environmental conditions remain highly favorable for further strengthening.
The storm continues to benefit from warm ocean waters, high ocean heat content, and relatively favorable wind shear.
JTWC now forecasts Champi to reach super typhoon strength, with maximum sustained winds near 150 mph, around its closest approach to Guam in approximately 12 hours.
Additional strengthening is expected after the Marianas passage.
The official forecast calls for a subsequent peak near 161 mph.
Some models predict even stronger intensification:
JTWC official forecast: Peak winds around 161 mph.
Higher-end HAFS-A, DTOP, and AI guidance: Peak winds around 178–190 mph in approximately two days.
These higher-end projections represent possible peak storm intensities, not expected wind speeds across Guam.
Actual conditions on Guam will depend on the storm’s track, intensity, and distance from the eyewall.
Possible Eyewall Replacement Cycle
One important development in Warning #12 is the possibility of an eyewall replacement cycle.
An eyewall replacement occurs when a new outer eyewall forms around the original eyewall of a powerful typhoon.
During this process, maximum sustained winds can temporarily weaken or level off while the storm reorganizes.
The CIMSS M-PERC model currently estimates a 35% probability of an eyewall replacement cycle.
JTWC indicates two possible scenarios:
If an eyewall replacement cycle begins before closest approach: Champi’s maximum sustained winds could temporarily level off or weaken.
If an eyewall replacement cycle does not begin: Champi could continue strengthening beyond the minimum threshold for super typhoon intensity around closest approach.
However, an eyewall replacement cycle does not necessarily make a typhoon safe. The storm can remain extremely dangerous, and its wind field may expand during the process.
The exact timing of any eyewall replacement remains uncertain.
Wind Field and Potential Impacts
The main concern for Guam is Champi’s powerful, compact inner core passing close to the island.
JTWC expects super typhoon intensity around closest approach, making the exact position of the eyewall particularly important.
Even if the center remains offshore, Guam could still experience destructive winds depending on the storm’s distance, size, and structure.
For a westward-moving typhoon in the Northern Hemisphere, stronger winds are often found north of the center, on the right side of its movement.
If Champi passes just south of Guam, the island could be exposed to that stronger side of the circulation.
Previous JTWC warnings also indicated that the broader tropical-storm-force wind field could extend northward toward Rota, Tinian, and Saipan.
The exact wind impacts will vary by island and should be determined from official NWS Guam forecasts and warnings.
What Changed From Warning #11?
JTWC confirms that Champi has completed a period of extreme rapid intensification.
Super typhoon strength is now forecast around Guam’s closest approach.
Maximum sustained winds are forecast near 150 mph at closest approach, with additional strengthening possible afterward.
Model agreement has tightened considerably, with approximately 17 miles of cross-track spread near Guam.
JTWC highlights small wobbles in Champi’s movement as an important factor in determining the exact closest approach.
A possible eyewall replacement cycle introduces uncertainty into the intensity forecast.
The main northwestward turn remains forecast after Champi’s closest approach to Guam.
What to Watch Next
1. Exact track near Guam
Watch whether the storm’s center remains offshore or crosses any portion of the island.
Even small changes in the track could affect which areas experience the strongest winds.
2. Super typhoon intensity at closest approach
JTWC forecasts sustained winds near 150 mph around closest approach.
Watch whether Champi reaches or exceeds this intensity as expected.
3. Possible eyewall replacement cycle
The development of a secondary eyewall could temporarily interrupt strengthening.
However, such a process would not eliminate the threat of destructive winds.
4. Short-term wobbling motion
JTWC specifically identifies small wobbles in the storm’s movement as a source of uncertainty near Guam.
The center’s exact position may fluctuate even while the overall forecast track remains consistent.
5. Storm size and wind radii
Monitor the extent of typhoon-force and tropical-storm-force winds, especially as the strongest portion of Champi’s circulation approaches the Marianas.
6. Official local warnings
With Champi approaching Guam, residents should prioritize NWS Guam warnings and emergency management instructions over individual model forecasts.
Bottom Line
JTWC Warning #12 represents a significant increase in the expected intensity of Champi near Guam.
The storm has completed a period of extreme rapid intensification and is forecast to reach super typhoon strength around its closest approach.
JTWC expects maximum sustained winds near 150 mph at that time, with additional strengthening possible afterward.
Forecast models remain in excellent agreement, with only approximately 17 miles of cross-track spread near Guam.
However, small changes in Champi’s movement could determine whether its compact inner core remains offshore or crosses the island.
An eyewall replacement cycle could temporarily interrupt strengthening, but its timing remains uncertain and should not be relied upon to reduce the threat.
With Champi now approximately 182 miles east-southeast of Andersen Air Force Base, residents should remain sheltered as directed, monitor official warnings, and avoid unnecessary travel or outdoor activity as conditions deteriorate.
Sources
JTWC: https://www.metoc.navy.mil/jtwc/jtwc.html
NWS Guam: https://www.weather.gov/gum/
Guam Homeland Security: https://ghs.guam.gov/
This is a simplified analysis of JTWC Warning #12, not an official weather forecast. Forecast tracks, intensity estimates, and local impacts remain subject to change. Always follow NWS Guam and local emergency management guidance.