Complex sentence: By October 9, upper-level conditions had worsened substantially, and as a result, significant weakening initiated: cloud patterns gradually decreased in organization, and convective cloud tops warmed significantly as the system sped over progressively cooler waters.
Split into simpler sentences: By October 9, upper-level conditions had worsened substantially, resulting in a trend of significant weakening. Cloud patterns gradually decreased in organization, and convective cloud tops warmed significantly as the system sped over progressively cooler waters.