The 2017 North Atlantic tropical cyclone season was among the most active in the last two decades, with 17 named storms, of which six reached the major hurricane (MH) intensity: Harvey, Irma, Jose, Lee, Maria, and Ophelia. In this study, the water vapor sources for precipitation for these six MHs were examined using a Lagrangian approach. The particle dispersion model, FLEXPART, was used to identify moisture sources. Overall, the North Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico were identified as the main moisture sources, supplying ∼75%–85% of the atmospheric humidity gained by tropical cyclones, which resulted in precipitation associated with the MHs. However, the South Atlantic Ocean also contributed considerable humidity (∼14%–20%), and the remaining ∼1%–5% originated from the tropical eastern Pacific Ocean. The accumulated moisture uptake higher than the 90th percentile generally appeared within approximately 3° to 5° of the TC trajectory.
On 12–15 March 1993, a severe winter storm (SC93) formed over the Gulf of Mexico, affecting the Caribbean Islands and the eastern coast of the United States (US) and Canada with a notable amount of precipitation, snow and severe local storms. In this study, we investigate the origin of the precipitation generated by SC93 by applying a widely used Lagrangian moisture source diagnostic method. Our findings revealed that most of the moisture came from the western North Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico. Moreover, the eastern US and Mexico acted as notable terrestrial moisture sources. Overall, the moisture contribution from the oceanic origin was higher than the terrestrial counterpart, and the moisture sources progressively shifted northward as the storm moved. In addition, the moisture uptake mainly occurred in the cyclone–anticyclone interaction region.
Future changes in the intensity of tropical cyclones (TCs) under global warming are uncertain, although several studies have projected an upward trend in TC intensity. In this study, we examined the changes in the strength of TCs in the twenty-first century based on the Hurricane Maximum Potential Intensity (HuMPI) model forced with the sea surface temperature (SST) from the bias-corrected CMIP6 dataset. We first investigated the relationship between the mean lifetime maximum intensity (LMI) of major hurricanes (MHs) and the maximum potential intensity (MPI) using the SST from the Daily Optimum Interpolation SST database. The LMI of MHs and the MPI in the last two decades was, on average, 2–3% higher than mean values in the sub-period 1982–2000, suggesting a relationship between changes in MPI and LMI. From our findings, the projected changes in TC intensity in the near-future period (2016–2040) will be almost similar for SSP2-4.5 and SSP5-8.5 climate scenarios. However, TCs will be 9.5% and 17% more intense by the end (2071–2100) of the twenty-first century under both climate scenarios, respectively, compared with the mean intensity over the historical period (1985–2014). In addition, the MPI response to a warmed sea surface temperature per degree of warming is a 5–7% increase in maximum potential wind speed. These results should be interpreted as a projection of changes in TC intensity under global warming since the HuMPI formulation does not include environmental factors (i.e., vertical wind shear, mid-level moisture content and environmental stratification) that influence TC long-term intensity variations. Highlights The maximum potential intensity (MPI) of tropical cyclones is a predictor of their climatological intensities. Tropical cyclones will be 17% more intense than today by the end of the 21st Century. The maximum potential wind speed will increase by 5–7%/ºC under global warming.
<p align="justify"><span><span>Tropical cyclones (TCs) are one the principal natural hazards for coastal regions in tropical and subtropical latitudes. On a global scale, around 90 TCs form annually, and approximately 16% of them originated in the North Atlantic (NATL) basin. Heavy rainfall, one of the major hazards associated with TCs, can cause catastrophic flash flooding, landslide and related health and socio-economic problems. Therefore, understanding the precipitation origin during the passage of TCs is important to significantly aid in disaster mitigation and risk analysis. This work seeks to identify the origin of precipitation moisture within the TCs outer radius in the NATL basin from 1980 to 2018 by applying a Lagrangian moisture tracking method to air parcel trajectories. The TC information (intensity and position) was retrieved from the HURDAT2 database, while the outer radius was from the TCSize dataset. The pathways of air parcels that precipitated within the TC outer radius were obtained from the global outputs of the FLEXible PARTicle dispersion (FLEXPART) model fed by ERA-Interim reanalysis provided by the European Center for Medium-Range Weather Forecasts. The spatial moisture sources pattern exhibited a north-south split around 10&#186;N, coinciding with the mean position of the Intertropical Convergence Zone (ITCZ) during the boreal summer. The highest moisture contribution (~39%) during the genesis and peak of maximum intensification was from the tropical Atlantic Ocean north of ITCZ, including ~11% from the Caribbean Sean and ~6% from the Gulf of Mexico, followed by the western NATL (WNATL) with 23.8% and eastern NATL (ENATL) with 16.6%. Curiously, ~10% of moisture was from the Atlantic Ocean south of ITCZ and ~2% from the eastern Pacific Ocean. During the dissipation phase, the moisture sources shifted poleward as TCs moved, with the highest moisture support (~60.3%) from the subtropical north Atlantic Ocean (WNATL + ENATL) and ~11.2% from the NATL north of 50&#186;N. This behaviour shows that moisture sources for TCs precipitation are located circa to their positions. Indeed, by investigating the moisture uptake pattern along the TCs trajectories, we detected that the highest moisture uptake generally occurred within 3-5&#186; from the TC track. Likewise, the moisture uptake within 2000 km from the TC centre was approximately two times higher during the rapid intensification than during the slow intensification process. Furthermore, the relative position of moisture sources to the TC centre changed from 24 hours before the extratropical transition (ET) process to 24 hours after. That is, before ET, the moisture sources were located in the southwest-south sector, while after ET appeared in the west-southwest sector. Overall, this work provides new insights into the TCs' climatology in the NATL basin. Additionally, these findings can be used as a reference to understand future changes in the origin of precipitation moisture for TCs precipitation under different climate changes scenarios. </span></span></p>
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