SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
143 PM EDT MON APR 25 2022

GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/

COR

FORECAST DISCUSSION FROM APR 25/18 UTC: AT MID/UPPER LEVELS...THE
GLOBAL MODELS INITIALIZE A HIGHLY AMPLIFIED SINUSOIDAL WAVE
PATTERN...WITH LONG WAVE RIDGE ALONG 110W/120W INDUCING THE
NORTHWARD AMPLIFICATION OF A TROUGH BETWEEN 100W AND THE
BELLINGSHAUSEN SEA TO THE NORTHERN REGIONS OF CHILE/MID SECTIONS
OF SOUTH AMERICA. EMBEDDED IN THIS FLOW...A STRONG VORTEX LIFTS
ACROSS THE SOUTHEAST PACIFIC TO THE SOUTHERN REGIONS OF CHILE
LATER TODAY. THIS WILL SLOWLY PULL ACROSS SOUTHERN CHILE/PATAGONIA
IN ARGENTINA TO THE WESTERN ATLANTIC LATER ON TUESDAY. STARTING ON
TUESDAY EVENING...AS IT MOVES SOUTH OF THE BUENOS AIRES
PROVINCE...THE VORTEX WILL EXPERIENCE A RAPID RATE OF
INTENSIFICATION AS ENHANCED BY COUPLED JETS ALOFT. AT LOW LEVELS
THIS PATTERN WILL LEAD TO BOMB CYCLOGENESIS OVER THE SOUTHWEST
ATLANTIC...WITH SURFACE LOW DEEPENING FROM A 996 HPA LOW JUST
SOUTH OF BUENOS AIRES ON TUESDAY EVENING...TO A 952 HPA LOW EAST
OF THE MALVINAS LATER ON WEDNESDAY. THE INTENSIFYING SURFACE
CYCLONE REACHES MAXIMUM INTENSITY ON THURSDAY AS IT MOVES NEAR THE
SOUTH GEORGIA ISLANDS. AT LOW LEVELS THIS WILL BE ACCOMPANIED BY
HURRICANE INTENSITY WINDS...PEAKING AT 65-70KT ON TUESDAY THROUGH
THURSDAY MORNING.

AS SUCCESSIVE FRONTAL PERTURBATIONS LIFT ACROSS THE SOUTHEAST
PACIFIC INTO THE SOUTHERN REGIONS OF CHILE...THIS WILL RESULT IN
SEVERAL DAYS OF INTENSE PRECIPITATION AMOUNTS. STARTING TODAY
EXPECTING RAINFALL MAXIMA OF 50-100MM...WHILE ON TUESDAY TO
WEDNESDAY EXPECTING ADDITIONAL AMOUNTS OF 20-45MM/DAY. ACROSS THE
SOUTHERN AND CENTRAL ANDES OF CHILE THIS WILL PHASE CHANGE TO
SOLID PRECIPITATION ON TUESDAY THROUGH WEDNESDAY...WITH
ACCUMULATION OF 20-35CM ON TUESDAY AND 15-30CM ON WEDNESDAY...FOR
STORM TOTAL AMOUNTS OF 1.5-2.0 METERS. OVER MID SECTIONS OF SOUTH
AMERICA...THE EVOLVING UPPER LEVEL PATTERN WILL HELP SUSTAIN A
STRONG BAROCLINIC BOUNDARY BETWEEN THE RIO DE LA PLATA BASIN AND
URUGUAY/NORTHERN ARGENTINA. STRONG UPPER LEVEL VERTICAL WIND SHEAR
WILL CONTRIBUTE TO ENHANCE HELICITY AND ROTATION TO LIKELY FAVOR
LONG LASTING SEVERE WEATHER PRODUCING THUNDERSTORMS ACROSS
URUGUAY-ENTRE RIOS AND PORTIONS OF CORRIENTES IN ARGENTINA.
INITIALLY EXPECTING RAINFALL AMOUNTS OF 75-150MM AS ENHANCED BY
THE UPPER LEVEL JET...WITH AN ADDITIONAL 35-70MM ON
TUESDAY...WHILE ON WEDNESDAY THE MAXIMA WEAKENS TO 25-50MM. A
DRYING TREND IS THEN EXPECTED ACROSS THE SOUTHERN CONE ON
THURSDAY...AS THE FRONTAL LOW BOMBS NEAR THE SOUTH GEORGIA ISLANDS
AND A POLAR RIDGE BUILDS ACROSS THE SOUTHERN CONE.

AS THE AFOREMENTIONED LONG WAVE TROUGH LIFTS ACROSS THE SOUTHERN
CONE...IT WILL PRESS AGAINST A BROAD CELL OF THE SUBTROPICAL RIDGE
TO THE NORTH...WITH THE LATTER EXTENDING WEST-TO-EAST BETWEEN
24S-08S...WHILE CELL OF THE SUBEQUATORIAL RIDGE TO THE NORTH
DOMINATES THE FLOW ACROSS NORTHERN SOUTH AMERICA. THE DUAL
BARRELED RIDGE PATTERN WILL RESULT IN A BROAD AREA OF UPPER
DIVERGENCE ACROSS EQUATORIAL SOUTH AMERICA. THIS WILL VENT
CONVECTIVE DEVELOPMENT ACROSS NORTHERN BRASIL-THE
GUIANAS/VENEZUEAL TO COLOMBIA-NORTHERN PERU AND ECUADOR. IN THIS
AREA EXPECTING RAINFALL AMOUNTS OF 15-25MM/DAY...WITH MAXIMA
INCREASING TO 25-50MM AS ENHANCED BY PERTURBATIONS IN THE LOW/MID
LEVEL EASTERLIES. OTHER CONVECTION IS EXPECTED ALONG THE NORTHEAST
COAST OF BRASIL BETWEEN ESPIRITO SANTO AND EASTERN BAHIA...WHERE A
TRAILING SHEAR LINE AND TRADE WIND CONVERGENCE IS TO RESULT IN
AREAS OF MODERATE RAINFALL AMOUNTS.

DAVISON...WPC (USA)