Mark A. Boothe

The Pre-Depression Investigation of Cloud-Systems in the Tropics (PREDICT) Experiment: Scientific Basis, New Analysis Tools, and Some First Results

The principal hypotheses of a new model of tropical cyclogenesis, known as the marsupial paradigm, were tested in the context of Atlantic tropical disturbances during the National Science Foundation (NSF)-sponsored Pre-Depression Investigation of Cloud Systems in the Tropics (PREDICT) experiment in 2010. PREDICT was part of a tri-agency collaboration, along with the National Aeronautics and Space Administrations Genesis and Rapid Intensification Processes (NASA GRIP) experiment and the National Oceanic and Atmospheric Administrations Intensity Forecasting Experiment (NOAA IFEX), intended to examine both developing and nondeveloping tropical disturbances. During PREDICT, a total of 26 missions were flown with the NSF/NCAR Gulfstream V (GV) aircraft sampling eight tropical disturbances. Among these were four cases (Fiona, ex-Gaston, Karl, and Matthew) for which three or more missions were conducted, many on consecutive days. Because of the scientific focus on the Lagrangian nature of the tropical cyclogen...

Accuracy of Atlantic and Eastern North Pacific Tropical Cyclone Intensity Forecast Guidance

Abstract Five statistical and dynamical tropical cyclone intensity guidance techniques available at the National Hurricane Center (NHC) during the 2003 and 2004 Atlantic and eastern North Pacific seasons were evaluated within three intensity phases: (I) formation; (II) early intensification, with a subcategory (IIa) of a decay and reintensification cycle; and (III) decay. In phase I in the Atlantic, the various techniques tended to predict that a tropical storm would form from six tropical depressions that did not develop further, and thus the tendency was for false alarms in these cases. For the other 24 depressions that did become tropical storms, the statistical–dynamical techniques, statistical hurricane prediction scheme (SHIPS) and decay SHIPS (DSHIPS), have some skill relative to the 5-day statistical hurricane intensity forecast climatology and persistence technique, but they also tend to intensify all depressions and thus are prone to false alarms. In phase II, the statistical–dynamical models SH...

Observational Evidence for Alternate Modes of Track-Altering Binary Tropical Cyclone Scenarios

Abstract An observational study of western North Pacific tropical cyclones (TC) revealed many cases of two TCs whose tracks were altered by processes that were quite different from the mutual advection (Fujiwhara-type) processes. Thus, four conceptual models are proposed to describe these track alterations. A conceptual model called direct interaction is proposed that is a modification of one by Lander and Holland and has three modes: 1) a one-way influence in which the track of a smaller TC that is embedded in the circulation of a larger TC has a cyclonic orbiting motion, but no significant track alteration of the larger TC is apparent; 2) a similar case in which a mutual advection occurs with the tracks of both the smaller and larger TCs being altered; and 3) a subset of 2) in which the mutual advection includes an attraction component such that the two similarly sized TC circulations eventually merge into a larger circulation with a single center. During the 7-yr period (1989–95), the one-way influence...

Examining the Roles of the Easterly Wave Critical Layer and Vorticity Accretion during the Tropical Cyclogenesis of Hurricane Sandy

AbstractThe tropical cyclogenesis sequence of Hurricane Sandy is examined. It is shown that genesis occurs within a recirculating Kelvin cat’s-eye flow of a westward-propagating tropical wave. The cat’s-eye flow is able to provide a protective environment for the mesoscale vortex to grow and is characterized by gradual column moistening and increased areal coverage of deep cumulus convection. These findings are generally consistent with a recently proposed tropical cyclogenesis sequence referred to as the “marsupial paradigm.” Sandy’s cyclogenesis provides a useful illustration of the marsupial paradigm within a partially open recirculating region, with the opening located south of the pouch center. It is suggested that the opening acts to enhance the genesis process because it is adjacent to an environment characterized by warm, moist air, conditions favorable for tropical cyclogenesis. From a dynamical perspective, accretion of low-level cyclonic vorticity filaments into the developing vortex from sever...

Dynamical Tropical Cyclone 96- and 120-h Track Forecast Errors in the Western North Pacific

Abstract The Joint Typhoon Warning Center has been issuing 96- and 120-h track forecasts since May 2003. It uses four dynamical models that provide guidance at these forecast intervals and relies heavily on a consensus of these four models in producing the official forecast. Whereas each of the models has skill, each occasionally has large errors. The objective of this study is to provide a characterization of these errors in the western North Pacific during 2004 for two of the four models: the Navy Operational Global Atmospheric Prediction System (NOGAPS) and the U.S. Navy’s version of the Geophysical Fluid Dynamics Laboratory model (GFDN). All 96- and 120-h track errors greater than 400 and 500 n mi, respectively, are examined following the approach developed recently by Carr and Elsberry. All of these large-error cases can be attributed to the models not properly representing the physical processes known to control tropical cyclone motion, which were classified in a series of conceptual models by Carr ...

Weighted Position and Motion Vector Consensus of Tropical Cyclone Track Prediction in the Western North Pacific

Abstract Two approaches are developed and tested to improve the unweighted position consensus for 96-, 108-, and 120-h tropical cyclone track guidance in the western North Pacific. A weighted position guidance technique uses a weighting factor for each model that is inversely proportional to how far the 60-, 66-, and 72-h positions of that model are from the corresponding positions of the 11-member position consensus. The weighted position consensus of 96-, 108-, and 120-h track errors for a sample of 24 storms during the 2006 season are consistently smaller than for the unweighted position consensus. In the second approach, a weighted motion vector consensus is developed that uses the same weighting factors as in the weighted position consensus, except that the weights are applied to 12-h motion vectors between 84 and 120 h. This weighted motion vector consensus has substantially smaller errors than the unweighted position consensus, and results in smoother tracks when one or more of the model tracks dro...

Assessment of Western North Pacific 96- and 120-h Track Guidance and Present Forecastability

Abstract Because the Joint Typhoon Warning Center (JTWC) has only four dynamical models for guidance in making 96- and 120-h track forecasts, an opportunity exists for improving the consensus forecast by the proper removal of a likely erroneous forecast to form a selective consensus (SCON). Forecast fields from all four models [the U.S. Navy Operational Global Atmospheric Prediction System (NOGAPS), the U.S. Navy version of the Geophysical Fluid Dynamics Laboratory model (GFDN), the Met Office (UKMO) model, and the Global Forecast System (GFS)] were available during the 2005 western North Pacific season to evaluate for the first time the error mechanisms leading to large track errors. As shown previously for the NOGAPS and GFDN models during the 2004 season, error sources related to the midlatitude circulations accounted for about 90% of all large 120-h track errors by all four models during the 2005 season. This dominance of midlatitude-related error source is a major shift from the 72-h errors, which in...

Statistical postprocessing of NOGAPS tropical cyclone track forecasts

Abstract A statistical postprocessing technique is developed and tested to reduce the U.S. Navy global model (NOGAPS) track forecast errors for a sample of western North Pacific tropical cyclones during 1992–96. The key piece of information is the offset of the initial NOGAPS position relative to an updated (here best-track) position that will be known by 6 h after the synoptic times, which is when the NOGAPS forecast is actually available for use by the forecaster. In addition to the basic storm characteristics, the set of 24 predictors includes various segments in the 0–36-h NOGAPS forecast track as well as a 0–36-h backward extrapolation that is compared with the known recent track positions. As statistically significant regressions are only found for 12–36 h, the original 36-h to 72-h NOGAPS track segment is simply translated to the adjusted 36-h position. For the development sample, the adjusted NOGAPS track errors are reduced by about 51 n mi (95 km) at 12 h, 35 n mi (65 km) at 36 h, and 28 n mi (52...

A Simple Statistical-Synoptic Track Prediction Technique for Western North Pacific Tropical Cyclones

Abstract A simple statistical-synoptic technique for tropical cyclone (TC) track forecasting to 72 h in the western North Pacific is derived. This technique applies to the standard (S) pattern/dominant ridge region (S/DR) and poleward/poleward-oriented (P/PO) combinations, which are the two most common and represent about 73% of all situations. Only eight predictors that involve present and past 12-h and 24-h positions, intensity, and date are used. The track predictions are simple to calculate and understand; are available in near–real time each 6 h; apply at all intensities, as compared to the complex global or regional dynamical model predictions that are only available each 12 h at about 3–4 h after synoptic time; are not calculated for weak TCs; and tend to have accurate predictions only for tropical storm stage and above. The statistical-synoptic technique for S/DR cases has an improvement (skill) relative to the operational climatology and persistence (WPCLPR) technique of 12% after 12 h and 24% af...