Relationship of environmental relative humidity with North Atlantic tropical cyclone intensity and intensification rate

Abstract

.[1] Quantifying the relationship of large-scale environmental conditions such as relative humidity with hurricane intensity and intensity change is important for statistical hurricane intensity forecasts. Our composite analysis of 9 years of Atmospheric Infrared Sounder (AIRS) humidity data spanning 198 Atlantic tropical cyclones (TCs) shows that environmental relative humidity (ERH) above the boundary layer generally decreases with time as TCs evolve. Near the surface, ERH stays approximately constant. ERH generally increases with increasing TC intensity and intensification rate. Rapidly intensifying TCs are associated with free tropospheric ERH more than 10% (relative to the averaged ERH for all TCs) larger than that for weakening TCs. Substantial azimuthal asymmetry in ERH is also found, especially for the TCs attaining the highest intensities and largest intensification rates at distances greater than 400 km away from the TC center. In the front-right quadrant relative to TC motion, rapid intensification is associated with a sharp gradient of ERH in the upper troposphere, with a decrease from the near to the far environment between 400 hPa and 300 hPa. The ERH gradient weakens with the decrease of intensification rate. This radial ERH gradient might be a useful predictor for the statistical forecast of TC intensification. Citation: Wu, L

Predictability of Tropical Cyclone Intensity Evaluated through 5-yr Forecasts with a Convection-Permitting Regional-Scale Model in the Atlantic Basin

“…Calculations using different variables including CIN, lifted index (LI; both calculated using surface air parcels), mixing ratios, and precipitable water, within different radii or different levels, were also examined and the results were generally consistent. Wu et al (2012) also showed that low-level (1000-925 hPa) RH has the most horizontal homogeneity compared with other levels. The calculations of all environmental factors are included in Table 1.…”

An overview of the TROPICS NASA Earth Venture Mission

“…Shu and Wu () suggested that, in weakening storms, dry air penetrates to smaller storm radius than in intensifying storms, usually in the quadrants to the left of the storm motion. Wu et al () found more moist conditions within 200–400 km of the storm centre in intensifying and RI storms compared to weakening storms. A major unknown is whether the dry air acts to potentially weaken TCs through modification of precipitation structure or overall convective activity (Braun et al ).…”

Impacts of climatic variables on cyclone in the coastal regions of Bangladesh

“…The maximum of total mean has found in the month of July (88%) which was much higher than the July for whole Bangladesh, recorded 81.78% (BBS, 2009). In cyclone occurring months specially from August to October, the mean value of the coastal region is on around 84~88% and in May to 86% both of which indicate n for the formation of cyclone as Wu et al (2012) showed. In fact, Khulna, Mongla, Khepupara and Barisal area are mostly responsible for creating deep depression if the RH plays any role to the formation of cyclone, as the highest amount of RH has n this area, though Satkhira showed the lowest amount of RH in these months.…”

“…Study on this parameter is also important because temperature and RH relates t (Lawrence, 2004;Skilling, 2009) and RH has a good influence on the formation of cyclone (Kaplan and DeMaria, 2003;Emanuel et al, 2004;Hendricks 2010;Kaplan et al, 2010). Wu et al (2012) showed that about 82% RH is responsible for the occurrence of North Atlantic Tropical cyclone. So, RH above this level is very much responsible for the formation of cyclone in the coastal region of Bangladesh.…”