Tropical Storm Mun (04W) - Tropical Cyclone Advisory #4, 0000 UTC 7/3/25

…Tropical Storm Mun intensifying over open waters…

Current storm information:

• Position: 27.0°N 145.2°E

• Movement: NW at 6 knots (10 km/h)

• Intensity: 45 knots (85 km/h)

• Central pressure: 1000 hPa

Trend:

• Some additional strengthening is forecast during the next 24 hours.

Watches and warnings:

• There are no land-based watches or warnings in effect.

Hazards affecting land:

• None.

Discussion:

Mun (named by JMA at 1800 UTC) is quickly getting its act together. The tropical storm appears to be positioning itself underneath an upper-level trough, which has broken the southerly flow that had been shearing the system. Mun’s associated convection has very quickly wrapped around and into the circulation center, although a substantial tongue of dry air remains embedded within the circulation. Microwave imagery suggests a mid-level eye feature may also be developing near the center. The system also has impressive radial outflow, which will probably aid it in mixing out the dry air. The intensity is increased to 45 kts, giving extra weight to a recent SATCON estimate of 47 kts and Dvorak fixes of T3.0 from KNES and PGTW, and KNES’s Dvorak fix has a caveat that the system may be stronger than currently estimated.

Mun is not expected to be a threat to land. Most of the available model guidance suggests that Mun will take a rather erratic northward track over the open Pacific well east of Japan during the next few days as the subtropical ridge waxes and wanes in strength. Environmental conditions should be fairly conducive for strengthening, and Mun may briefly reach typhoon strength by Saturday. On Saturday, however, Mun will begin to encounter steadily cooling waters, which should cause a steady weakening trend. There are currently no indications that Mun will encounter any baroclinic zones as it journeys northward, and so the most likely forecast is that Mun loses its convection and becomes a post-tropical cyclone by the end of the forecast period. 

Forecast positions and maximum winds

• 00 hrs: 27.0°N 145.2°E – 45 kts

• 12 hrs: 28.6°N 144.9°E – 50 kts

• 24 hrs: 29.8°N 144.8°E – 55 kts

• 48 hrs: 31.1°N 146.3°E – 65 kts

• 72 hrs: 32.7°N 148.9°E – 50 kts

• 96 hrs: 35.9°N 149.4°E – 40 kts

• 120 hrs: 39.6°N 150.8°E – 35 kts Post-tropical