Tropical Depression 17W Forms Northeast of Guam23.8N 161.2E
Tropical depression 17W, located approximately 780 nm northeast of Hagatna, Guam, has tracked west-northwestward at 09 knots over the past six hours. Maximum significant wave height is 10 feet.
Low level structure evident in recent microwave satellite imagery and a Dvorak intensity estimate of 30 knots indicate that TD 17W has formed just poleward of a tropical upper tropospheric (TUTT) cell.
The system is tracking west-northwestward along the southern periphery of a deep subtropical ridge to the north. This general motion is expected to continue through the next 24 hours.
Thereafter, a developing midlatitude trough to the north is expected to weaken the steering ridge and induce a poleward turn into a weak steering environment. The available numerical guidance is in good general agreement with this scenario, although there is some uncertainty in the exact track given the expectation of a weak steering setup.
Unfavorable environmental factors, including persistent upper level convergence, easterly vertical wind shear, and the introduction of drier air toward the center of TD 17W from the southeast, should prevent the system from intensifying significantly and eventually result in dissipation below the 25 knot warning threshold intensity around TAU 48.