Tropical Depression Alvin Discussion Number 14
Wiki-Hurricanes Forecast Center
8:00 PM PDT Fri Jun 28 2019
There is not much left to Alvin tonight. Conventional satellite imagery shows that the low-level circulation has become increasingly ill-defined, while associated shower activity (not much convection to speak of) has been whisked away to the north under the influence of strong southwesterly wind shear. The 0z satellite intensity estimate from SAB had fallen to T2.0/30kt, similar to the current UW-CIMSS ADT estimate of T2.2/32kt. While current intensity values are higher, a testament to how rapid Alvin has weakened since last night, the culmination of 20kt of wind shear, mid-level relative humidity values near 50 percent, and ocean temperatures near 23C is likely to have weakened Alvin at the rate suggested by strict Dvorak evaluation. Therefore, the initial intensity is lowered to 30kt, and Alvin is now a tropical depression.
Upper-level winds, already hostile, are only expected to increase. And while ocean temperatures should remain steady around 23C, mid-level relative humidity values are too forecast to fall, to around 25 percent within 36 hours! This extremely hostile environment does not bode well for Alvin, and it is likely to become a remnant low within the next 12 hours. Dissipation is expected in about 2 days. The storm has been moving on a north of west-northwest track today, but this motion should soon become more westerly as Alvin loses vertical depth and becomes steered by low-level easterly trade winds.
FORECAST MAX WINDS
INIT 29/0300Z 30 KT 35 MPH
12H 29/1200Z 25 KT 30 MPH...POST-TROP/REMNT LOW
24H 30/0000Z 20 KT 25 MPH...POST-TROP/REMNT LOW
36H 30/1200Z 20 KT 25 MPH...POST-TROP/REMNT LOW