This week at the HPC/OPC/SAB Proving Ground at the World Weather Building, the focus was on the use of the RGB products from NASA SPoRT. Once Irene finished impacting the East Coast, there was no rest for the weary as Katia was born in the Eastern Atlantic and a Tropical Depression (TD13) formed in the Central Gulf. The images below were captured on 09/02 and shows how useful the RGB products are in identifying different airmasses that interact with these tropical systems.
Figure 1: This is a sample image from the SEVIRI-derived RGB Airmass product courtesy of NASA SPoRT. The red circles (from left to right) depict Hurricane Katia and two tropical waves that have emerged off the coast of Africa. The yellow boundary is the location of the dry airmass coincident with the Saharan Air Layer (SAL) outbreak. This is a weak outbreak, therefore the exact boundary is difficult to pinpoint on this image. Some dry air (light shading of red) to the north of the upper boundary might be related to the SAL, but that is hard to distinguish in this image as there is a good mix of warm, moist, tropical air (green) and dry (red) air. You can ignore the purple/red areas west of Katia as this is a product of the boundary conditions in the product and not reliable indication of mid-latitude influence. There is an upper-low to the northwest of Katia, but you would need a better image to confirm the interaction.
Figure 2: In this figure, you can see through the SEVIRI RGB Dust product that the expanse of dust (light pink shading) within the SAL is much larger than the dry air would indicate in the Airmass product.
Figure 3: The SAL-tracking product from CIMSS/NOAA-HRD shows the dust outbreak over the Eastern Atlantic. This outbreak is rather weak, therefore it doesn’t show up well. A blend of all of these products could prove quite useful for tropical cyclone forecasting.
Figure 4: The GOES-Sounder RGB Airmass product from 09/02/11 shows an upper-level low influencing the development of TD13 in the Gulf of Mexico. The yellow ellipse highlights the small dry pocket (red) associated with the upper-low that appears to the west of the depression. This does not look as though it will be a major impediment to development as the upper-low is filling rapidly, most likely due to the increase in latent heating from the intense convection.