Kona Day One
COAMPS-simulated 7-day accumulated landfall precipitation (mm) ending by 0000 UTC 17 Feb 2019, showing (a) the control, along with the difference between the (b) 75%, (c) 50%, and (d) 25% kona low experiments and the control experiment.
Kona Day One
Because of the nature of this solution technique, the flow field beyond the specified 6 radius of influence will also be altered. This is evident in Fig. 4, which shows 320-K potential temperature, 850-hPa vorticity, and IVT for the control NAVGEM analysis valid on 0000 UTC 10 February, both before and after the kona low was removed from the NAVGEM analysis. One can see, for example, that the process effectively not only removes the kona low, but also impacts the surrounding areas such as reducing the IVT to east of Hawaii at the COAMPS initial time. One also sees perturbations extending outward to the lateral boundaries, although to a lesser extent. The solutions discussed are thus best cast in light of the removed circulation as well as impacts that will come through the lateral boundary conditions.
At the initial model time on 10 February, the kona low from the NAVGEM analysis already has a well-defined sea surface pressure center (Fig. 3a), a warm core above 300 hPa (not shown) and a cold core in the lower levels. The kona low vortex is vertically aligned with little vertical tilt evident in either the circulation or thermodynamic variables at this time (Fig. 9a). In the center of the kona low, the air is relatively dry with higher moisture values evident in the peripheral regions of the circulation (Fig. 9b). There is a strong lateral moisture gradient extending to the southeast, along the southern boundary of the surface high pressure center located farther to the northeast. There is also a low pressure center farther to the east of the surface high between 40 and 60N. Both the surface high and the upper-level trough are outside the COAMPS northern boundary at the model initial time but are evident in the NAVGEM analysis (Fig. 3a).
On 11 February, the eastern flank of the kona low connects with the westward and poleward tropical moisture surge south of 10N latitude (Figs. 9c,d). On 12 February, the lower portion of the kona low circulation is stretched farther toward the southeast as the AR continues to intensify and surge toward the U.S. West Coast (Figs. 9e,f). 041b061a72