American Meteorological Society Demo

at http://dx.doi.org/10.1175/BAMS-88-8-Wimmers). ponents of the TC structure (eyewalls, bands) and This sequence follows Ivan during its first of two behavior (trends, secondary eyewall formation, eyeERCs and its brush with Jamaica (from 1200 UTC wall replacement cycles). However, in many cases the 10 September to 1200 UTC 11 September). This limited spatial resolution of the microwave imagery animation clearly depicts not only the emergence of prevents the observation of very small (subpixel) eyes the secondary eyewall and the subsequent decay of and finer convective filaments that connect the inner the inner eyewall, but it also depicts how these events rainbands to the eyewall. transpired within the erratic track of the storm over Not surprisingly, another general characteristic that time (consistent with the National Hurricane of the MIMIC-TC product is that its accuracy in Center best-track path) in conjunction with its en- depicting the visual continuity of structural changes counter with Jamaica. decreases with the increasing time gap between Finally, an example from Hurricane Rita (2005) successive microwave images (displayed as the time was chosen because it is effective at showing the “away” in the upper-right corner of the animation). limitations of the MIMIC-TC product (Fig. 5). As Based on experience from viewing dozens of tropical in the other examples, the MIMIC-TC depiction cyclones, we find that beyond about 3 h from an matches radar in depicting the overall behavior of actual microwave observation, the morphed product the storm structure. However, the eyewall is de- begins to lack definition and is less likely to give picted somewhat differently in the two products. In proper information about eyewall asymmetries and MIMIC-TC, the eyewall is a shifting assortment of size. convective cells, whereas in the radar, the eyewall is made up of thin, curved precipitation filaments with MIMIC-IR. Geostationary infrared imagery and considerably shorter lifetimes. The eyewall does not LEO microwave imagery are complementary tools achieve a closed ring of convection until approxi- for viewing tropical cyclones, and it is common for mately 0000 UTC 20 September, and before that time tropical cyclone analysts to utilize both to achieve the radar shows that the irregularity in the eyewall the optimum interpretation of storm position and shifts and rotates quickly with the entrainment of structure. To this end, an additional visualization inner bands and advection of convective cells. Clearly, tool has been created—MIMIC-IR—which overlays the microwave data do not update quick ly enough to capture this evolution, and the fade process is not optimal in this case, so inconsistencies exist at the scale of the eyewall (Fig. 5). However, despite the inability to capture details, the MIMIC-TC animation does effectively depict the degree of organization within the eyewall as it increases in radial symmetry toward 0000 UTC 20 September. Overall, these examples FIG. 5. Comparison of (left) MIMIC-TC product with NEXRAD 0.5° elevademonstrate the usability tion radar reflectivity composited from four sites (right) for Hurricane Rita of the MIMIC-TC prod(2005) from 1200 UTC 20 September to 0400 UTC 21 September. Time resolution of MIMIC-TC is 15 min; time resolution of radar composite is 7.5 uct and provide guidance min. Radar is spatially composited according to the nearest station (marked for interpreting it effecwith a magenta cross) to each pixel. The MIMIC-TC product is created t ively. By high light ing from 8 microwave satellite passes. Labels are as follows: (upper left label) convection-driven over NHC-reported maximum sustained winds ("Vmax"); (upper right label) the stratiform precipitation, temporal separation from the microwave overpass nearest in time (either MIMIC-TC distinctly presbefore or after); (magenta perimeter) radar composite domain; (magenta ents the dominant com"+") radar station positions. AMERICAN METEOROLOGICAL SOCIETY AUGUST 2007 | 1195 http://dx.doi.org/10.1175/BAMS-88-8-Wimmers

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