Today featured significantly less convective activity in the S-PolKa domain than the previous two days.  While the 200 hPa synoptic map (left panel of Figure 1) shows that the near equatorial region near Gan and the Revelle have southeasterlies, most of the southern DYNAMO array has easterlies. Conditions at 700 hPa (center panel of Figure 1) are characterized by light and variable winds near Gan and the Revelle and easterlies near Diego Garcia and the Mirai. At 925 hPa (right panel of Figure 1) the entire southern DYNAMO array is characterized by easterlies.  Figure 2 shows that soundings taken in Male, Gan, Diego Garcia, and at the Revelle at 0601 UTC have light winds through 200 hPa. While Diego Garcia and the Revelle have an easterly component through the depth of the troposphere, Male and Gan have a small region of westerlies at approximately 750 hPa (2 - 3 km altitude). This wind profile is consistent with the maps discussed in Figure 1. Additionally, each of the soundings have dry conditions above 600 hPa. The upper levels have exhibited a drying trend for the last few days in association with large-scale subsidence. Figure 3 shows a large maximum of positive 200 hPa velocity potential over the central Indian Ocean. Positive upper level velocity potential is indicative of convergence and sinking motion through the column. Evidence of large-scale subsidence is also seen in the soundings. Each of the soundings in Figure 2 have a slight subsidence inversion at approximately 550 – 500 hPa. Brandon Kerns also notes this large-scale subsidence in the 14 November 1800 UTC Daily Weather Briefing. 

The most significant convection today was west of the DYNAMO array. Figure 4 (top) indicates that a large amount of lightning occurred in the half hour preceding 0531 UTC. This high flash frequency was observed throughout the day in these two regions. The bottom panel of Figure 4 indicates that the infrared temperatures at 0531 UTC in the three electrically active convective centers were near 200 K.

Within the S-PolKa domain, the day started with a number of large cold pools. Not only were these cold pools evident in the reflectivity, but they were also associated with large differential reflectivity values, which has been a common occurrence throughout DYNAMO (top panels of Figure 5). Vertical cross sections through these cold pools indicate that these features extended to approximately 800 m in altitude. The differential reflectivity (upper right panel of Figure 5) had exceptional high values near islands, especially on the western side of Addu Atoll. These are some of the highest differential reflectivities we have observed and it is unclear why this enhancement is occurring.

The top panel of Figure 4 shows that the belt of convection that has been affecting the S-PolKa domain for the last few days has moved to the south. Thus, S-PolKa was located between the strong convection to the northwest and the belt of larger cumulus to the south. During the late afternoon shallow cumulus and cumulonimbus began to form in northwest - southeast oriented lines as illustrated in the top panel of Figure 6. Infrared temperatures at 1101 UTC (bottom panel of Figure 6) indicate that the temperatures were only about 260 K. At later times, cloud top temperatures reached a minimum of 250 K. These shallow lines of cumulus, when viewed in time lapse, were oriented and moved from northeast to southwest. This motion is consistent with northeasterly flow observed at low levels throughout the day in the Gan soundings (upper right panel of Figure 2).

A representative example of afternoon convection observed in the S-PolKa domain today is shown in Figure 7. Even the strongest cells barely reached 8 km and quickly dissipated. The shallow band of westerlies noted in the Gan sounding above (upper right panel of Figure 2) is evident in Figure 7 as a band of outbound velocities at approximately 3 km.  Figure 8 visually shows the variation of the cloud population throughout the day. Morning convection was limited to shallow cumulus (left panel). However, by early afternoon deeper cumulus began to form in lines (center panel) and isolated cumulonimbus developed in the late afternoon (right panel). Additionally, the left panel of Figure 8 shows that the anvils were shearing towards the east, which is uncommon.