APPLICATION OF TROPICAL CYCLONE LIFE-CYCLE PREDICTIONS FROM PRE-FORMATION STAGE: EASTERN NORTH PACIFIC 2021 SEASON

This thesis documents advancements made during the 2021 season test of pre-formation tropical cyclone (TC) forecasts in the eastern North Pacific (ENP) using Marchok vortex tracker outputs from the European Centre for Medium-Range Weather Forecasts ensemble. Critical Warm Core Magnitude thresholds are established to predict Time-to-Formation and Time-to-Hurricane timings and positions along 15-day Weighted-Mean Vector Motion ensemble tracks. This thesis develops and tests a decision flowchart to assist forecasters in the critical task to efficiently select the pre-formation ensemble storms most likely to become TCs, and to non-select false alarm storms. The flowchart effectiveness is demonstrated, and validations of these techniques are provided for hurricanes Enrique and Felicia, strong Tropical Storm (TS) Guillermo and weak TS Jimena, and a non-developing disturbance. Thus, an opportunity exists for TC warning centers to provide accurate long-range intensity and track predictions of potential TCs from the pre-formation stage. This thesis is prepared as guidance to forecasters to facilitate integration of these techniques into operational centers and increase forecast confidence at much earlier stages of developing and non-developing TCs. While this thesis confirms the effectiveness of this forecast process for ENP pre-formation TCs, the findings suggest a promising capability for application in other basins.Office of Naval Research, 875 N. Randolph Street, Suite 1425, Arlington, VA 22203-1995Captain, United States Air ForceApproved for public release. Distribution is unlimited