Tuesday, 17 April 2018
Champions DEFGH (Sawgrass Marriott)
John A. Knaff, NOAA Center for Satellite Applications and Research, Fort Collins, CO
Cold lows, also called TUTT cells, are the antithesis of tropical cyclones. Their structure is displays a nearly vertical cold core low structure with warm anomalies located in the local stratosphere and colder anomalies in the troposphere below. Cyclonic winds are strongest at rather large radii and at the level of zero horizontal temperature gradient moving toward the center and maximize just below the local tropopause, which is sloped upward from the center. The structure of cold lows have long fascinated tropical meteorologists, as they often dictate the local vertical wind shear variations over the trade wind regions of the planet and sometime interact with low-level weather systems. These have been hypothesized to be the foci of the atmospheric sinking within the subtropical ridge, and thus are likely important for stratospheric/tropospheric exchange. There are also documented linkages between seasonal variations of cold lows, variations in tropical cyclone activity, and the seasonal variability and strength of the subtropical highs. Nonetheless, there are not many climatological studies detailing the movement and inter-annual variability nor satellite presentation of these systems.
To provide a short-term climatology of cold lows in and around the Atlantic tropical cyclone basin, this study constructs subjectively analyzed tracks of cold lows over a 10-year period (2007-2016) during June-October using the GOES-East satellite’s water vapor channel, which has remained at the same central wavelength and covers a 140W to 10W domain. Using these tracks, I construct mean monthly cold low frequencies and trajectories, and cold low and environmental diagnostics via model analyses. Finally, using the GOES-E satellites water vapor channel, I construct mean water vapor structure of these systems in a motion following framework created and decompose the resulting variance structures, which may provide forecaster insight and the possibility of subjectively forecasting cold low intensification and dissipation. This presentation will present these results and discuss future work including construction of a trajectory-based climatology and persistence (CLIPER) model for cold low movement and verification of numerical model forecasts of cold lows using both the tracks and the CLIPER model.
Disclaimer: The views, opinions, and findings contained in this report are those of the authors and should not be construed as an official National Oceanic and Atmospheric Administration or U.S. Government position, policy, or decision.
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