Prognostic Meteorological Discussion
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000
FXSA20 KWBC 021654
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1253 PM EDT TUE JUN 02 2015

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

MODEL DISCUSSION (VALID FROM JUN 02 AT 0000 UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS CONTINUE IN VERY GOOD AGREEMENT ON FORECAST
EVOLUTION. THEY SHOW DISCREPANCIES ON THE EVOLUTION TO THE SOUTH
OF 25S AFTER 120 HRS...AND OVER THE DRAKE PASSAGE INTO THE
SOUTHERN ATLANTIC AFTER 96-108 HRS...ESPECIALLY ON THE EXACT TRACK
OF A POTENT TROUGH EXPECTED TO MOVE NORTHEASTWARD ALONG THE
BELLINGSHAUSEN SEA INTO THE SOUTH ATLANTIC DURING FRIDAY/SATURDAY.

SEASONAL WET PATTERN TO CONTINUE IN SOUTHERN CHILE AT LEAST
THROUGH THE WEEKEND...SLOWLY EXPANDING NORTH. A TIGHT BELT OF
WESTERLIES HAS ESTABLISHED ACROSS THE SOUTHERN CONE...INITIALLY
CENTERED BETWEEN 35S-45S THROUGH THURSDAY...BUT THEN RELOCATING TO
30S-40S INTO THE WEEKEND. SEVERAL SHORT WAVE TROUGHS ARE EMBEDDED
IN THIS FLOW. ALTHOUGH PRECIPITABLE WATER WILL NOT BE EXTREMELY
HIGH...LIMITING TO 30-35MM IN MOISTER SUBTROPICAL MOISTURE
CONNECTIONS FROM THE TROPICAL PACIFIC...THE DYNAMICS WILL BE
FORMIDABLE TO CONTINUE SUSTAINING ROUNDS OF MODERATE RAINFALL FOR
CHILE. A SHORT WAVE TROUGH WILL CROSS THE ANDES DURING TUESDAY
EVENING PRODUCING HEIGHT FALLS BETWEEN SANTIAGO AND TEMUC0 OF
50-75GPM. THIS TROUGH WILL ALSO HEIGHT FALLS IN ARGENTINA...BUT
MOISTURE IS LIMITED EAST OF THE ANDES. ASSOCIATED WITH THIS
TROUGH...EXPECTING RAINFALL AMOUNTS BY TUESDAY INTO EARLY
WEDNESDAY TO FOCUS BETWEEN INTERIOR REGIONS OF THE BIO BIO REGION
INTO THE AYSEN REGION WITH MAXIMA OF 20-35MM/DAY. BY WEDNESDAY
INTO EARLY THURSDAY EXPECTING LARGEST ACCUMULATIONS BETWEEN ISLA
CHILOE INTO THE NORTHWESTERN MAGALLANES REGION WITH MAXIMA OF
10-15MM/DAY. THE NEXT ORGANIZED AND POTENT UPPER TROUGH WILL
ARRIVE INTO SOUTHERN CHILE DURING THURSDAY. THIS WILL ESTABLISH A
NEW SUBTROPICAL MOISTURE CONNECTION...BUT ONCE AGAIN STRONG
DYNAMICS WILL BE THE KEY FACTOR FOR MODERATE RAINFALL AMOUNTS.
STRONG UPPER DIVERGENCE IN THE POLAR EXIT OF THE UPPER JET...IS TO
INTERACT WITH ENHANCED LOW-LEVEL MOISTURE CONVERGENCE AND WINDS
EXCEEDING 50KT AT 850 HPA TO PRODUCE ACCUMULATIONS OF 25-50MM/DAY
BETWEEN TALCA AND OSORNO/VALDIVIA. WEAK COLD FRONT AND BASE OF
UPPER TROUGH WILL MEANDER NORTHWARD AS WILL DECREASING
PRECIPITATION. BY FRIDAY INTO EARLY SATURDAY EXPECTING
ACCUMULATIONS OF 20-35MM/DAY TO EXTEND FROM TEMUCO INTO THE ANDEAN
FOOTHILLS OF THE OHIGGINS REGION.

TO THE EAST OF THE SOUTHERN ANDES...MOISTURE IS LIMITED WHICH WILL
CONTINUE LIMITING RAINFALL ACCUMULATIONS. MOISTURE TRANSPORT FROM
TROPICAL SOUTH AMERICA WILL START RE-ESTABLISHING DURING WEDNESDAY
INTO THURSDAY. A COLD FRONT IS EXPECTED TO RAPIDLY ORGANIZE ALONG
THE URUGUAY-BRASIL BORDER AND THEN INTO NORTHEASTERN ARGENTINA
DURING WEDNESDAY...TO THEN ADVANCE INTO RIO GRANDE DO SUL AND
CORRIENTES WHERE IT WILL BECOME STATIONARY ON FRIDAY. THIS WILL BE
THE FOCUS FOR CONVECTION. BY THURSDAY INTO EARLY FRIDAY EXPECTING
ACCUMULATIONS OF 05-10MM/DAY ACROSS PARAGUAY AND MAXIMA OF
15-20MM/DAY IN NORTHEASTERN ARGENTINA/NORTHERN URUGUAY INTO
SOUTHERN BRASIL. BY FRIDAY INTO EARLY SATURDAY EXPECTING MAXIMA TO
INCREASE TO 20-40MM/DAY CONCENTRATING OVER URUGUAY AND EXTREME
SOUTHERN BRASIL. AMOUNTS WILL START DECREASING AFTER AS ACTIVITY
RELOCATES OFFSHORE.

OTHER REGION OF INTEREST IS A FRONT TO EXTEND ACROSS EXTREME
SOUTHERN MINAS GERAIS AND INTO NORTHERN PARAGUAY BY TUESDAY
EVENING...TO START WEAKENING AFTERWARDS. INITIALLY...THIS FRONT
WILL CONTINUE BEING THE FOCUS FOR LOW-LEVEL MOISTURE CONVERGENCE
ACROSS SOUTHERN MINAS GERAIS/NORTHERN SAO PAULO/MATO GROSSO DO SUL
WHERE EXPECTING MAXIMA OF 15-30MM/DAY. OVER RIO DE JANEIRO AND
SOUTHERN ESPIRITO SANTO EXPECTING MAXIMA OF 05-10MM/DAY. BY
TUESDAY INTO WEDNESDAY EXPECTING AN ACTIVATION OF CONVECTION ALONG
THE EASTERN COAST OF BRASIL AS EXITING UPPER JET INTERACTS WITH
REMNANT CONVECTIVE INSTABILITY NEAR AND TO THE NORTH OF THE
WEAKENING FRONT. AIDED BY TRADE WINDS APPROACHING 25-30KT AT
925-850 HPA...EXPECTING ACCUMULATIONS TO INCREASE TO MAXIMA OF
15-30MM/DAY. A NEW SURGE IN ACTIVITY IN THIS REGION IS EXPECTED BY
FRIDAY INTO SATURDAY WHEN EXPECTING THE DEVELOPMENT OF A COASTAL
TROUGH FROM RIO GRANDE DO NORTE SOUTH INTO NORTHERN ESPIRITO
SANTO. THIS IN COMBINATION WITH ENHANCED CONVECTIVE INSTABILITY
WILL LEAD TO ACCUMULATIONS INCREASING TO MAXIMA OF 15-20MM/DAY.

NORTH OVER THE CONTINENT MOST ACTIVITY WILL CONCENTRATE NEAR
EQUATORIAL LOCATIONS IN THE FORM OF ISOLATED THUNDERSTORMS MOSTLY
TO THE NORTH OF 03S-05S.  EXPECTING A SURGE IN ACTIVITY ACROSS THE
AMAZON DELTA ON THURSDAY INTO FRIDAY WITH MAXIMA INCREASING TO
20-35MM/DAY. TO THE WEST...WARM SEA SURFACE TEMPERATURES CONTINUE
SUSTAINING ACTIVE PATTERN OF CONVECTION OVER THE INTERIOR COAST OF
ECUADOR. WINDS WILL BECOME MORE FAVORABLE FOR THE ENHANCEMENT OF
LATE AFTERNOON MOISTURE CONVERGENCE DURING THURSDAY INTO EARLY
FRIDAY...WHEN EXPECTING ACCUMULATIONS TO INCREASE TO MAXIMA OF
15-30MM/DAY WHERE THUNDERSTORMS DEVELOP.

CHARPENTIER...DMC (CHILE)
CISNEROS...UNALM (PERU)
ROMERO...DMC (CHILE)
GALVEZ...WPC (USA)
$$




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