The case study has been reprocessed at pixel by pixel resolution and one iteration of the physical retrieval step. It has been used ECMWF hybrid levels (137 levels) GRIB files from t+00 to t+24 every hour with high spatial resolution (0.125º x 0.125º) from the 10th August 2016 00UTC run.
As can be seen in the loop of 10th August 2016 normalized natural RGB images strong convection took place the 10th August 2016 in the mountains of the south of Iberian Peninsula (Andalucia region).
Note: The RGB images are made after normalization of VIS channel radiances to enhance the contrast at twilights and improve comparison.
Animated
GIF with a selection of several fields. (top left) iSHAI ML field,
(top center) ECMWF ML field, (top right) TOZ field, (bottom left)
iSHAI BL field, (bottom center) ECMWF BL field, (bottom right) KI
stability index for the 10th
of
August 2016.
It can be seen in the iSHAI TOZ field on the animated GIF of the Figure above that one cold air core in high levels is approaching to the south of Iberian Peninsula from the north. Cold air in high and medium levels is one of the ingredients for convection.
At least in Spain, for nowcasting purposes the monitoring of the precipitable water on the medium layer is very important to determine the region where convection could be triggered. Also, this is the layer with greatest added value from satellite due to the MSG WV channels. It could be seen in loops of iSHAI images every 15 minutes that there is an area with moist air in medium levels in the south of Iberian Peninsula (likely trapped by the pass of a cold front the day before by the orography). In the Figure above, the loop of iSHAI ML images and iSHAI BL images are shown as a summary. In this case study, the humid air at the south of Iberian Peninsula is other main ingredient for the convection. The convection started at 15 UTC at the mountains of south of Iberian Peninsula (Andalusia) where orographic factors combined with the above ingredients meet.
It is a good idea to have the possibility to show the background NWP fields in the same projection, colour palette and time that the iSHAI outputs. This provides the spatial structure that can be hidden by the clouds. It is possible with one slight modification of iSHAI code (hereafter GEO-PGE00 tool; it is one internal AEMET tool) to get the parameters calculated directly from ECMWF GRIB files interpolated temporal, vertical and spatially to MSG images for the region. The loop of BL and ML images from ECMWF Hybrid profiles are also shown in the Figure above. The forecasted moist air region and the advection of humity in the Guadalquivir River valley is clearly shown.
In the animated gif below, the loop of the images of vertical cross sections of the normalized 3D arrays of T, q and θe are shown as one example of 3D interactive use by users of iSHAI and ECMWF netCDF files from Hyb mode. It can be seen clearly the entrainment of the cold air in high levels over the low and medium levels moist air region.
Animated
GIF with the vertical cross section of (top left) iSHAI normalized T
profiles, (bottom left) ECMWF normalized T profiles red indicates
warmer than mean and blue indicates colder than mean; (top center)
iSHAI normalized q profiles, (bottom center) ECMWF normalized q
profiles green indicates more humid than mean and beige indicates
more dry than mean; (top right) iSHAI θe
normalized
profiles, (bottom right) ECMWF normalized θe
profiles
red and yellow indicates more θe
than
mean and a vertical gradient indicates instability. Loop of image for
the 10th
of
August 2016.