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Domain 9: Central South America
Chile, Central and Northern Argentina, Uruguay, Paraguay and Southern Brazil
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.
 
 
Potential for severity and hail - GR02.CMD
Highlights regions with the potential for severe convection, and specifically hail in Central South America. The potential increases when red (fuscia) contours appear with red (fuscia) boxes inside.
 
 
Potential for severity and hail - GR02T.CMD
GR02T: Risk for Severity. GR02T highlights regions with the potential for severe convection in shades of colors. Gray suggests a risk for strong convection. But green, red and fuscia shades generally relate to marginal/slight, moderate and elevated risk, respectively. The risk increases is boxes appear over color shaded areas. This indicates that deep-layer instability is present, among other potential enhancers.
Specific Risk for Hail: The estimation of the potential for hail was included from GR02 (Galvez and Santayana, 2019), an algorithm specifically designed to detect the potential for hail in mid latitudes of South America. The risk for hail increases when red/fuscia boxes appear encircled by red/fuscia contours, and 500 hPa temperatures < -9°C. If these areas appear over color shaded areas, the risk for hail increases.
 
 
Identification of fronts - FRONT.CMD
Highlights surface fronts based on horizontal gradients in a field constructed using thickness of 1000-850hPa and 1000-925 hPa; dewpoint at 1000 and 925 hPa; and precipitable water. Plots an average of 1000 and 925 hPa streamlines and wind barbs in kt (gray and black), 1000-850 hPa thickness in GPM (green contours), and the magnitude of the gradient in light blue, yellow and fuscia contours. The 18°C 2m dewpoint contour is included.
 
 

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: Thursday, 12-Mar-2020 18:06:34 UTC