Abstract:

The western North Pacific Ocean (NPAC) was a hotbed of tropical cyclone (TC) activity during September 2022. Noteworthy TCs included Hinnamnor, Muifa, Merbok, Nanmadol, Talas, Noru, and Kulap. In terms of overall impacts, TC Merbok was noteworthy for undergoing a spectacular extratropical transition (ET) in the west-central NPAC and bringing high winds and flooding rains to western Alaska. At issue, is whether, and to what extent, TC Hinnamor may have played a role in the formation of TC Merbok. The potential linkage between TCs Hinnamnor and Merbok is a potential vorticity (PV) streamer that reconfigures itself into a westward-moving cutoff cyclone near 170 E. This PV streamer/cutoff cyclone can be traced back to the extratropical transition of TC Hinnamnor. Noteworthy, is that the configuration of the precipitation shield around TC Merbok is consistent with a storm that was initially cold core before it transitioned into a warm-core system. A question of interest is to what extent the eventual ET of TC Merbok influenced downstream ridge building near Alaska which via downstream baroclinic development influenced the downstream formation of a deep trough offshore of California. The “meteorological shenanigans” over the WPAC and CPAC associated with the aforementioned multiple TCs and TC-TC interactions will be documented in this presentation. An important and intriguing research question question is what physical and dynamical processes matter the most for downstream impacts associated with recurving and transitioning TCs in conjunction with poleward-directed moisture surges. TC Merbok is a “poster child” for pretty much every conceivable dynamical process associated with TC-TC, TC-trough, and TC-ridge interactions. Also at issue is to what extent the ET process governs multiple interacting TCs that are recurving into higher latitudes in downstream baroclinic development cases. A question that also has to be asked is whether and to what extent the poleward-directed flux of bodacious tropical moisture is at the top of the “ET food chain”.