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The Weather Prediction Center

12. Southern Tropical South America  
Bolivia / Peru / Northern Paraguay / Western and Central Brazil
Graphics use 1° GFS Model Output

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.
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. Note that GR02 works better is 500 hPa temperatures < -8°C.
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.
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: Thursday, 12-Mar-2020 18:07:07 UTC