By PDC’s Senior Weather
Specialist Glenn James
Tropical Cyclone 21W…is located approximately 327 NM east of Saipan
Northeast Pacific Ocean:
>>> Near the coast of Southern Mexico:
A small area of low pressure located near the coast of southern Mexico is producing limited shower and thunderstorm activity.
Any development of this system over the next few days is likely to be slow to occur due to unfavorable upper-level winds and proximity to land. The system is forecast to move west-northwestward to westward near the southern coast of Mexico during the next few days.
* Formation chance through 48 hours…low…10 percent
* Formation chance through 5 days…low…20 percent
There are no tropical cyclones nor any areas of disturbed weather under investigation by the CPHC
Northwest and Southwest Pacific Ocean, Indian Ocean, Arabian Sea:
Northwest Pacific Ocean
Tropical Cyclone 21W
According to the JTWC Warning number 3, sustained winds were 25 knots with gusts to near 35 knots.
Animated enhanced infrared satellite imagery depicts a compact, symmetrical area of convection displaced slightly southeastward of a partially exposed low level circulation center (llcc). The latest available microwave image showed weak low-level banding features to the northwest of an area of deep, but relatively disorganized convection.
A tropical upper tropospheric trough (tutt) cell is currently sitting due north of 21W, imparting a moderate northwesterly shear over the system as evidenced by the satellite depiction.
Finally, outflow is moderate towards the southwest, but is strongly divergent right over the system, providing support for the convection, which has persisted for the past six hours even in the face of the moderate shear.
A moderately strong upper-level trough will move across Japan and into the northwest Pacific and steadily erode the ridge from the west. The combined effects will push 21w onto an accelerating northward trajectory after 24 hours.
By 72 hours the system will begin to slow down as it approaches the tail end of a cold front trailing the extra-tropical low that develops ahead of the aforementioned trough.
By around 72 hours, the system will take a hard right turn, moving eastward along the remnant frontal boundary while transitioning to a extratropical cyclone as it becomes embedded within the baroclinic zone, is engulfed by mid-level dry air and moves into the right entrance region of a strong jet stream.
The system will be slow to intensity at first but once the tutt moves to the west, the rate of intensification will increase, but the system will continue to fight against moderate shear and increasingly dry air, putting a cap on the peak intensity. Strong dry air entrainment, cooler sea surface temperatures and increased shear will conspire to weaken the system after 72 hours, as it undergoes ett.
>>> There’s an area of disturbed weather, being referred to as Invest 97W which is located approximately 309 NM northwest of Guam
Animated multi-spectral satellite imagery depicts an obscured broad low-level circulation (llc) with most of the convection displaced to the south of the system. Another image pass shows that the llc remains broad and elongated with multiple circulations.
Environmental analysis indicates favorable conditions with low (05-10 knot) vertical wind shear, warm sea surface temperatures, and decent poleward outflow.
Global models agree on a slow north northwestward track with intensity guidance showing a gradual development over the next 24-48 hours.
Maximum sustained surface winds are estimated at 18 to 23 knots.
The potential for the development of a significant tropical cyclone within the next 24 hours remains medium.
>>> There’s an area of disturbed weather, being referred to as Invest 90W Puerto Princesa, Manila, Philippines
Animated multi-spectral satellite imagery depicts a poorly organized circulation with scattered flaring convection. Apartial pass shows 90W strong wind field in the northern quadrant ranging from 25-
Environmental analysis indicates favorable conditions for development with low (10-15 knot) vertical wind shear, warm sea surface temperatures, and strong poleward outflow.
Global models agree on invest 90W rapidly developing within the South
China Sea and tracking southwest towards Vietnam in the next 48-72 hours.
Maximum sustained surface winds are estimated at 12 to 18 knots.
The potential for the development of a significant tropical cyclone within the next 24 hours is upgraded to medium.