According to Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) satellite precipitation composites, a broad maritime area over the far eastern tropical Pacific and western Colombia houses one of the rainiest spots on Earth. This study aims to present a suite of mechanistic drivers that help create such a world‐record‐breaking rainy spot. Previous research has shown that this oceanic and nearly continental precipitation maximum has a strong early morning precipitation peak and a high density of mesoscale convective systems. We examined new and unique observational evidence highlighting the role of both dynamical and thermodynamical drivers in the activation and duration of organized convection. Results showed the existence of a rather large combination of mechanisms, including: (1) dynamics of the Choco (ChocoJet) and Caribbean Low‐Level Jets along their confluence zone, including the Panama semi‐permanent low; (2) ChocoJet deceleration offshore is favored by land breeze, enhancing the nighttime and early morning low‐level convergence; (3) a wind sheared environment that conforms to the long‐lived squall line theory; (4) action of mid‐level gravity waves, which further support the strong diurnal variability; and (5) mesoscale convective vortices related to subsidence in the stratiform region and top‐heavy mass flux profiles. This study emphasizes the multiscale circulation and thermodynamics mechanisms associated with the formation of one of the rainiest spots on Earth and showcases new observations gathered during the Organization of Tropical East Pacific Convection field campaign (OTREC; August–September, 2019) that support the outlined mechanisms.

Kelvin waves (KWs) play a key role in the synoptic variability of the tropics, accounting for up to 37% of the total variance in intraseasonal variability. Previous studies have shown KWs as precursors of extreme hydrometeorological events in the maritime continent. This study characterizes the seasonality of the waves, analyzes the influence of KWs over mean seasonal precipitation and extreme precipitation events over northern South America. Results show that MAM is the season with the highest cumulative events of KWs during the period 1981-2022 with more than 120 events. During MAM, positive (negative) precipitation anomalies predominate over northern South America (Amazon) coinciding with the Wet (dry) phase of the KW. The influence of KWs over Extreme precipitation Events (EPEs) show similar spatial patterns in the different seasons but one remarkable feature show that during Wet KWs: EPEs tend to enhance inland while decreasing offshore. Finally, we selected a flood event in Turbo, Colombia reported on May 9 2007 that was influenced by the passage of a convectively active KW that contribute with enhance low-level westerly flow convergence the previous days of the event. Knowing the influence of these intraseasonal oscillation on precipitation and extreme precipitation events is key for aiding the development of early warining systems and the improvement of weather forecast in the region.

Convectively Coupled Kelvin Waves (CCKWs) play a key role in synoptic variability and can trigger extreme hydrometeorological events. This study characterizes the influence of CCKWs on seasonal precipitation patterns and extreme precipitation events (EPEs) over northern South America. Using a filtered OLR dataset, we found that precipitation anomalies associated with CCKWs are sensitive to the selected index region. A sensitivity analysis identified a region in the Colombian Pacific exhibiting the strongest precipitation anomalies linked to CCKWs. At seasonal scales, March–May (MAM) is the season with the highest CCKW activity, and its convective phase is associated with enhanced precipitation over the far eastern Pacific, western Amazonia, and northern Colombia, while suppressed convection dominates northwestern Brazil. In addition, three regions exhibit increases of up to 30% in EPE occurrence during convective-phase Kelvin waves: (i) the northwestern Amazon, (ii) northwestern Colombia, and (iii) the Peruvian coast. In contrast, EPE occurrence in the Colombian Pacific appears largely independent of CCKW passage, likely due to the strong background climatological rainfall in the region. We also analyze a flooding event in Turbo, Colombia, on 9 May 2007, that occurred during the passage of a convective-phase Kelvin wave and was preceded by days of enhanced low-level southwesterly flow convergence and persistent rainfall. Understanding the influence of these intraseasonal oscillations on precipitation and EPEs is essential for improving regional weather forecasts and supporting the development of early warning systems.

According to TRMM and GPM satellite precipitation composites, a broad maritime area over the far eastern Tropical Pacific and western Colombia houses one of the rainiest spots on Earth. This study aims to present a suite of mechanistic drivers that help create such a world-record breaking rainy spot. Previous research has shown that this oceanic and nearly-continental precipitation maximum has a strong early morning precipitation peak and development of a high density of mesoscale convective systems. We examined new and unique observational evidence highlighting the role of both dynamical and thermodynamical drivers in the activation and duration of organized convection. Results show the existence of a rather large combination of mechanisms, including: (1) dynamics of the Choco (ChocoJet) and Caribbean Low-Level Jets along their confluence zone, including the Panama semi-permanent low; (2) land breeze favors ChocoJet deceleration offshore, enhancing the nighttime and early morning low-level convergence; (3) vertical wind shear and tilting of vertical wind shear into vorticity lines that interact with convective outflows; (4) action of mid-level gravity waves, which support the strong diurnal variability; (5) mesoscale convective vortices related to subsidence in the stratiform region in long lasting MCSs reinforcing (3); and (6) the likely role of land surface-atmosphere interactions and the rainforest over western Colombia. This study emphasizes the multi-scale environmental processes associated with the formation of one of the rainiest spots on Earth and showcases new observations gathered during the Organization of Tropical East Pacific Convection (OTREC; August-September, 2019) which support the outlined mechanisms.

This work is a second part contribution of the effect of intraseasonal oscillations on precipitation over the study region. The index generated for each wave (Part I) allow to classify events like convection inhibiting (dry) and convection favoring (wet) days and correlate with precipitation data from ERA5 and CHIRPS. Results show positive and negative precipitation anomalies across the region associated with each oscillatory process, which can be linked to anomalies in moisture transport and convection within the atmospheric column. During wet days, the Tropical Easterly Waves contribute up to 20% of precipitation over Caribbean Sea and eastern Pacific (and western Mexico), while the Kelvin waves accounts for 15% over the tropical eastern Pacific. On the other hand, Mixed Rossby-Gravity waves accounts for 15% of precipitation over the eastern Pacific (10°N - and western Mexico) during wet days and, 12% of precipitation on the Pacific coast of Central America during dry days. Finally, the Madden-Julian Oscillation contributes nearly 15% of precipitation over the Pacific coast of Mexico and Central America during wet days. These findings offer new insights into the spatial and temporal patterns within the region related to these intraseasonal oscillations.