A Climatology and Synoptic Composite Analysis of Very Small (a.k.a.: “Midget”) Tropical Cyclones undergoing Rapid Intensity Change

Very small, or “midget” tropical cyclones (TCs) (Arawaka 1952) are generally difficult to analyze and forecast due to underestimation of TC intensity by traditional methods, as well as the tendency of rapid intensity fluctuations by these very small storms. Their small size also means that there is likely less observational data to assimilate for numerical weather prediction. Further, their small size makes them less well-resolved by coarser grid-spacing models. Underestimation of analysis intensity can result in unreliable forecasts in regards to intensity, as well as a delayed issuance of initial warnings, especially if a TC develops near coastal regions. Insufficient research has been conducted in the last decade to improve understanding on how these very small cyclones form, and the impact of environmental factors on subsequent TC track and intensification. Recent research based upon a limited set of cases (Harr et al. 1996) suggests that midget TCs sometimes develop under dynamic forcing from monsoon gyres in the western North Pacific (WNP); however, a more robust climatology of this and other forcing mechanisms is needed. This research area is being revisited in light of the dramatic improvement in quality and density of operational gridded and remotely sensed datasets, including satellite data, over the past decade. Accordingly, the purpose of this study is to utilize these recent tools, and to develop new qualitative and objective tools, including the following: 1) a midget TC climatology, 2) guidance for early detection from available data, and 3) intensity prediction methods in order to increase forecast capabilities.