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Domain 7. Western South America
Graphics use 1° GFS Model Output


Terrain elevation in meters above sea level. Source: GFS0.25°(NOMADS-NOAA).

ALGORITHM GFS 00Z GFS 12Z
Enhanced GDI and Flow - EGDI.CMD
The Enhanced GDI (EGDI) is an enhanced version of the Galvez-Davison Index (GDI) that adds the detrimental effects of low relative humidity in the 300-400 hPa layer (also proxy for elevated inversions), the detrimental effects of upper convergence, the enhancing/detrimental effects of low-level moisture convergence/divergence, and a precipitable water enhancement factor. As the GDI, it helps to identify environments favorable for shallow convection, deep convection or deep convection with the potential for heavy rainfall. Loops include the low-level (1000-850hPa) and upper level (400-200hPa) flow to account for dynamic and orographic forcing, and movement of systems. It also plots 950-700 hPa convergence/divergence of the flux of mixing ratio, upper divergence (400-200hPa), and GDI advection and flux.
 
 
Central Andes Precipitation Accumulation Index - CAPI.CMD
Tool to evaluate the potential for types of precipitation amounts in the central Andes. CAPI is computed using 700-400 hPa mixing ratios (for column moisture content), 600-400 hPa relative humidity and its advection (for dry air entrainment), 700-500 hPa mixing ratio flux convergence and 300-200 hPa divergence (trigger and dynamically-driven ascent), 500-250 hPa shear (preservation of storm structure), and the Lifted Index (deep-layer instability). Boxes appear when the chance of precipitation increases, upon the climatological diurnal cycle of convection. The expected intensity is reflected in colors: green=light, light blue=moderate and fuscia=locally heavy amounts.
Also plotted, the enhanced GDI (>30, >45 and >60 in thick yellow, red and fuscia contours). The flow is the average of 600, 550, 500, 450 and 300 hPa in kt, to evaluate the origin of the air mass entering the Andes, storm cell motion and potential for 'trasvase'/spill over of precipitation into the coast.
Implemented on 27-Jan-2020. Last update: 07-Feb-2020.



 



 

Note: These algorithms are only forecast tools, not official forecasts. For information on the algorithms, click on the red text.

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Page last modified: Wednesday, 19-Feb-2020 17:25:32 UTC