Prognostic Meteorological Discussion
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000
FXSA20 KWBC 261623
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1222 PM EDT TUE JUL 26 2016

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

MODEL DISCUSSION (VALID FROM JULY 26 AT 0000 UTC): MODELS FOLLOW
SIMILAR EVOLUTION THROUGH 108-120 HRS...WITH ENSEMBLE MODEL
GUIDANCE PROVIDING SUPPORT TO THE DETERMINISTIC MODELS. CONFIDENCE
IN THE FORECAST IS HIGH.

AT 500 HPA...A SHORT WAVE TROUGH IS PULLING ACROSS ARGENTINA TO
THE WESTERN ATLANTIC...AND THROUGH 24 HRS IT IS TO CLEAR THE COAST
OF URUGUAY/SOUTHERN BRASIL. UNDER THE INFLUENCE OF COUPLED
JETS...THE TROUGH IS FORECAST TO RAPIDLY INTENSIFY EARLY IN THE
CYCLE. THROUGH 96-108 HRS THE MODELS CONTINUE TO FORECAST THE
TROUGH TO SLOWLY PULL TO THE EAST-SOUTHEAST. AT LOW LEVELS THIS
SUSTAINS A DEEPENING LOW/TROUGH OFF THE SOUTH COAST OF BRASIL. THE
ASSOCIATED FRONT PUSHES NORTH ACROSS SAO PAULO-MATO GROSSO DO SUL
TO NORTHERN BOLIVIA BY 24 HRS. BY 48-60 HRS...HOWEVER...IT WILL
START TO RETROGRESS AS A WARM FRONT ACROSS PARAGUAY. MOST ACTIVE
CONVECTION WITH THIS FEATURE IS EXPECTED EARLY IN THE CYCLE...TO
SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY ACROSS URUGUAY-SOUTHERN
STATES OF BRASIL.

FARTHER UPSTREAM...A 500 HPA TROUGH IS TO GRADUALLY PULL ACROSS
THE EASTERN SOUTH PACIFIC. AS IT PUSHES EAST THE TROUGH IS TO
PRESS AGAINST A MID/UPPER LEVEL RIDGE OVER CHILE/ARGENTINA.
THROUGH 54-60 HRS THE RIDGE WEAKENS ENOUGH TO ALLOW THE TROUGH TO
FINALLY MOVE INLAND INTO THE SOUTHERN REGIONS OF CHILE...AND BY
84-96 HRS IT IS TO MOVE INTO PATAGONIA/LA PAMPA TO CUYO IN
ARGENTINA. AT LOW LEVELS IT IS TO ALSO SUSTAIN A DEEPENING LOW
ACROSS THE FAR EASTERN PACIFIC. THIS IS TO SLOWLY MOVE EAST INTO
THE SOUTHERN REGIONS OF CHILE BY 42-48 HRS...WHERE IT IS TO FAVOR
STRONG BOUNDARY LAYER WINDS. THE ASSOCIATED SURFACE FRONT REACHES
SOUTHERN CHILE BY 48 HRS...AND THROUGH 72 HRS IT MOVES EAST INTO
PATAGONIA-CENTRAL CHILE. DEEP SUBTROPICAL MOISTURE IS TO ACCOMPANY
THIS BOUNDARY AS IT ENTERS SOUTHERN CHILE...TO SUSTAIN ORGANIZED
CONVECTION. STARTING AROUND 48 HRS THIS IS TO SUSTAIN MODERATE
CONVECTION WITH MAXIMA OF 15-25MM. THROUGH 72 HRS THIS INCREASES
TO 25-50MM...AND THROUGH 96 HRS IT IS TO DECREASE TO 15-20MM. BULK
OF THE HEAVY CONVECTION IS TO CLUSTER BETWEEN PUERTO MONTT AND
CONCEPCION CHILE...WHERE STORM TOTAL AMOUNTS ARE TO PEAK AROUND
100MM.

NORTH OVER THE CONTINENT...AT 200 HPA...A NEAR ZONAL WESTERLY FLOW
ESTABLISHED ACROSS PERU-BRASIL. THROUGH 72-84 HRS PATTERN WILL
GROW MORE AMPLIFIED...WITH SINUSOIDAL WAVE FEATURE TO ENVELOP AREA
TO THE NORTH OF 25S. AS THE PATTERN EVOLVES...LIGHT TO MODERATE
CONVECTION WILL CLUSTER ACROSS SOUTHERN COLOMBIA-NORTHERN
PERU/EASTERN ECUADOR AND NORTHERN AMAZONAS IN BRASIL. IN THIS AREA
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY...DECREASING TO 05-10MM
BY 60-84 HRS. OTHER CONVECTION IS EXPECTED ACROSS THE
GUIANAS...WITH RAINFALL AMOUNTS OF 05-10MM EXPECTED THROUGH 54-60
HRS...AND 10-15MM THEREAFTER.

AYALA...DINAC (PARAGUAY)
OSORIO...DMC (CHILE)
DAVISON...WPC (USA)
$$




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