TS Laura and Marco (resp. 13 & 14L)
Laura's satellite signature is surprisingly impressive for a tropical cyclone traversing over mountains. Infra-red satellite images show a well-defined mid-level circulation over south-central DR embedded under very intense convection. The upper level outflow is also well-established. This is probably a result of very favorable upper level environment, with low VWS (less than 10 knots). The airplane currently investigating the tropical cyclone has found flight level winds (700mb) of 55-60 knots and maximum reliable SFMR wind of 45-50 knots, suggesting the cyclone has strengthened some despite being over land. These winds are recorded in the northern quadrant of the system. Dropsode data does not indicate significant dry air entrainment and I suppose that the large convective mass has mixed out most of the dry air. The current intensity is thus estimated at 50 knots.
Even though the deepest convection is located closer to southern coast, cyclonic vorticity from low level wind field north of the island may still lead to reformation of center north of the MLC. Thus, I will not forecast a track as far west as the global models, for now. As a result, I will follow the HWRI more closely and anticipate a landfall in the vicinity of southwestern LA.
Intensity forecast is also challenging. My best bet is that the system will hold its strength (45 knots) during its track across DR and Hispaniola. After that, there is a 36 hour window of opportunity for it to take advantage of the very favorable environment and a period of rapid intensification seems probable. I will now forecast a 90 knot landfall (Category 2) but it should be noted that high intensities cannot be ruled out at this point.
After a period of faster intensification, the trend has slowed for Marco. It has moved into the Gulf of Mexico and the center is located east of previous forecast. One significant change since the previous discussion is that Marco is now forecast to adopt a more easterly track during the next day, probably as a response to upper level flow and it is now expected to make landfall over the northern Gulf coast, before turning more westward due to a building ridge. 12z data still support an intensity of 60 knots, a little below Category 1 hurricane threshold. VWS has increased to near 20 knots, in a SW'ly direction and shear is expected to continue to affect Marco. The combination of modest dry air and shear, offset by high SST, should lead to slow strengthening to a borderline hurricane over the Gulf and its eventual landfall as a strong TS/minimal hurricane.
Typhoon Bavi (West Pacific)
Bavi is now a 65-knot typhoon. This estimated is based on the higher of Dvorak classification of T4.0/kt and SATCON estimate of slightly over 50 knots. It is forecast to intensify to a peak of 90 to 100 knots over the East China Sea, as a result of very high (30-31C) SST, light VWS (the current subtropical jet will give way to southerly flow from a developing anticyclone). The only inhibiting factor is the presence of dry air associated with upper trough subsidence. Apart from a west shift in future track, the reasoning is largely the same as the previous discussion and the system is still anticipated to track mainly northward, closer toward Korean peninsula and Northeastern China.
It is not very common for northern China to experience a typhoon landfall. Typhoon typically recurves northeast well before this point, but in this case, intense Rossby wave breaking will give rise to a high latitude ridge in the Sea of Japan that will steer the cyclone northward.