HRD Seminar – Evan Forde – 26 September 2018

Mr. Forde presented a seminar titled “Identification of Atlantic Basin Tropical Cyclones in Proximity to Significant Dry Air Events in Total Precipitable Water Imagery (1987-2015)”.


A study analyzing total precipitable water (TPW) data from 1987-2015,  has identified 126 Atlantic basin TCs that were in proximity to significant dry air events (SDAEs) including Saharan Air Layers (SALs), during their life cycles.  We define an SDAE as an air mass at least one standard deviation drier than climatology for the specified study area. TPW can resolve moisture gradients and asymmetries beneath cirrus clouds and provide details about TCs in proximity to SALs, Mid Latitude Dry Air Intrusions (MLDAIs) and various air-moisture combinations. The yearly SDAE-TC proximity rate observed during this study varied from 8-60%, and the aggregate rate was 33%.   We also noted that sixty-eight percent of all SDAE-proximal TCs increased in intensity subsequent to their initial encounter and that forty-four percent of them ultimately became major hurricanes. This research demonstrates that TPW can be used to detect current as well past SDAE-proximal TCs and the historical regularity of these encounters establishes that they are a significant element in Atlantic basin TC climatology. 

A copy of the presentation is available on the anonymous ftp site:

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