## 4 Results and Discussion
### Impact of Different Scatterometer Product Resolutions
In front of the precipitating system winds shifted to southwesterly in contrast to the direction indicated by the coarser resolutions. The wind gradient magnitude over the area was reached a local maximum of 4 \(\times\) 10\({}^{-3}\) s\({}^{-1}\). Differences in the wind vectors between the UHR and the coarser resolution might have arisen from differences in the retrieval algorithms, as well as from the different model winds used in the ambiguity selection. While ASCAT winds at 50- and 25-km spatial resolution implement the ECMWF model for the MLE estimator, UHR process uses model winds from MERRA-2. [PERSON] and [PERSON] (2008) found that 50-km ASCAT winds performed better than ECMWF model winds against buoy wind measurements in the presence of rain-induced downdraft, pointing out that ECMWF does not resolve well the airflow near rain. Two main GFs were obtained in this case, for the primary and secondary threshold values of 6.8 \(\times\) 10\({}^{-4}\) s\({}^{-1}\) and 2 \(\times\) 10\({}^{-3}\) s\({}^{-1}\), respectively. Other smaller features behind the MCS were spurious due to the aforementioned low-quality retrievals. UHR spatial resolution allowed for small variations in the wind that could lead to a larger bias in the wind gradient field in comparison with the coarser resolution, therefore the secondary threshold used in the GF method was an order of magnitude higher. The GF that was characterized by the largest area, encompassed a large part of the precipitation. However, in front of the MCS, the outline of the feature was in agreement with the precipitation structure near the surface and the precipitation-induced outflow boundary. The feature offshore the coast of Houston was associated with increased wind gradient magnitude over an area that was affected by precipitation (Figure 6e). The radar analysis over the respective area (Figure 1), didn't reveal any change in the wind field before and after the overpass, which might have indicated that scatterometer wind retrievals were of low quality. At the overpass of ASCAT-B (Figure 6f) elevated wind speed magnitude (30 m s\({}^{-1}\)) was retrieved within the precipitating system, while the suggested wind direction was northwesterly. Wind gradient magnitude was small due to the homogeneity of the vectors over the area. A buoy located at 29.3\({}^{\circ}\)N 94.4\({}^{\circ}\)W (Figure 6b, 42035) indicated southesterly direction (153\({}^{\circ}\)N) at the closest time to the ASCAT-A overpass; however, measurements taken 30 min earlier (obtained every 10 min) reported northwesterly to northeesterly direction. Considering the delay in the response of the scatterometer at sudden wind changes, the surrounding UHR retrievals near the coast were in accordance with previous buoy measurements (Figure 6f). On the eastern side of the domain (Figure 6b, R1), the wind was southwesterly over an area free of precipitation (Figure 6f). In front of the system's precipitation border the wind direction shifted to southwesterly, with speed of the same magnitude (19 m s\({}^{-1}\)) as over the open ocean. The wind gradient field was characterized by fragments and large variations in magnitude along the front edge of the MCS. Fragments within the gust front have also being observed by high-resolution Doppler radars Uyedaand Zrnic [70], providing confidence that the 7-km resolution product can detect such fine-scale features. Multiple wind gradient features were identified in the UHR product during the overpass of ASCAT-B (Figure 6f, black solid polygons), with the largest feature capturing the wind shift in front of the MCS associated with the outflow boundary. The wind feature at the most eastern part of the domain (29.4\({}^{\circ}\)N 91.7\({}^{\circ}\)W) was characterized by wind gradient maximum, induced by a sudden change in the wind direction from southerly to northerly over the respective area. Two buoys (Figure 6b, AMRL1 and EINL1) located near the coast, measured northwesterly and northerly wind direction, respectively, indicating that the UHR retrieval was valid.