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Abstract As a part of the Tropical Cyclone Rapid Intensification (TCRI) project, we investigated thermodynamic conditions necessary for cyclone intensification. While high sea surface temperature and low tropospheric wind shear are well known environmental factors contributing to storm intensification, they are not sufficient to predict intensification and rapid intensification in particular. To explore thermodynamic factors contributing to intensification, we used dropsondes deployed in pre‐storm and storm environments interpolated on a regular grid via a 3D variational analysis. We find that in mesoscale convective areas an instability index, which measures the stability of the atmosphere to moist convection, and saturation fraction, which measures the moisture content of the atmosphere, show a narrow range of values favorable for intensification, and rapid intensification in particular. 

Abstract Studying convection, which is one of the least understood physical mechanisms in the tropical atmosphere, is very important for weather and climate predictions of extreme events such as storms, hurricanes, monsoons, floods and hail. Collecting more observations to do so is critical. It is also a challenge. The OTREC (Organization of Tropical East Pacific Convection) field project took place in the summer of 2019. More than thirty scientists and twenty students from the US, Costa Rica, Colombia, México and UK were involved in collecting observations over the ocean (East Pacific and Caribbean) and land (Costa Rica, Colombia). We used the NSF NCAR Gulfstream V airplane to fly at 13 kilometers altitude sampling the tropical atmosphere under diverse weather conditions. The plane was flown in a ‘lawnmower’ pattern and every 10 minutes deployed dropsondes that measured temperature, wind, humidity and pressure from flight level to the ocean. Similarly, over the land we launched radiosondes, leveraged existing radars and surface meteorological networks across the region, some with co-located Global Positioning System (GPS) receivers and rain sensors, and installed a new surface GPS meteorological network across Costa Rica, culminating in an impressive systematic data set that when assimilated into weather models immediately gave better forecasts. We are now closer than ever in understanding the environmental conditions necessary for convection as well as how convection influences extreme events. The OTREC data set continues to be studied by researchers all over the globe. This article aims to describe the lengthy process that precedes science breakthroughs. 

Abstract. The Organization of Tropical East Pacific Convection (OTREC) field campaign, conducted August through October 2019, focuses on studying convection in the eastern Pacific and the Caribbean. An unprecedented number of dropsondes were deployed (648) during 22 missions to study the region of strong sea surface temperature (SST) gradients in the eastern Pacific region, the region just off the coast of Columbia, and in the uniform SST region in the southwestern Caribbean. The dropsondes were assimilated in the European Centre for Medium-Range Weather Forecasts (ECMWF) model. This study quantifies departures, observed minus the model value of a variable, in dropsonde denial experiments and studies time series of convective variables, saturation fraction which measures moisture and instability index and deep convective inhibition which quantify atmospheric stability and boundary layer stability to convection, respectively.Departures are small whether dropsondes are assimilated or not, except in a special case of developing convection and organization prior to Tropical Storm Ivo where wind departures are significantly larger when dropsondes are not assimilated. Departures are larger in cloudy regions compared to cloud-free regions when comparing a vertically integrated departure with a cloudiness estimation. Abovementioned variables are all well represented by the model when compared to observations, with some systematic deviations in and above the boundary layer. Time series of these variables show artificial convective activity in the model, in the eastern Pacific region off the coast of Costa Rica, which we hypothesize occurs due to the overestimation of moisture content in that region.