Prognostic Meteorological Discussion
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000
FXSA20 KWBC 011701
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
101 PM EDT MON JUN 01 2015

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

MODEL DISCUSSION (VALID FROM JUN 01 AT 0000 UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS ARE IN EXCELLENT AGREEMENT ON THE EVOLUTION
OF THE LONG WAVE PATTERN THROUGH THE NEXT FIVE DAYS. THERE ARE
SOME DISCREPANCIES ON THE EVOLUTION OF SHORT WAVE TROUGHS
ESPECIALLY TO THE SOUTH OF 40S AFTER 96 HRS. THE UKMET MODEL IS
THE ONE STRUGGLING MORE WITH THE SHORT WAVE EVOLUTION. CONFIDENCE
IS HIGH THROUGH 96 HRS...AND DECREASES GRADUALLY TO THE SOUTH OF
40S AFTERWARDS.

WET PATTERN CONTINUES ESTABLISHING OVER SOUTHERN CHILE AS SEVERAL
SHORT WAVE TROUGHS ARRIVE ACCOMPANIED WITH SUBTROPICAL MOISTURE
CONNECTIONS AND FORMIDABLE DYNAMICS. A POTENT SHORT WAVE TROUGH IS
CROSSING THE ANDES ON MONDAY...TO EXTEND ALONG EXTREME EASTERN
ARGENTINA BY MONDAY EVENING. THIS TROUGH IS ACCOMPANIED BY A
SURFACE FRONT AND A SUBTROPICAL MOISTURE CONNECTION. ENHANCED
MOISTURE CONVERGENCE AT LOW-LEVELS WILL LEAD TO ANOTHER ROUND OF
MODERATE RAINFALL FOR SOUTHERN CHILE. THROUGH EARLY TUESDAY
EXPECTING ACCUMULATIONS OF 30-60MM/DAY BETWEEN LOS ANGELES AND
CHAITEN...AND MAXIMA OF 10-15MM/DAY BETWEEN CHAITEN AND SOUTHERN
AYSEN. EXPECTING ACCUMULATIONS IN PATAGONIA AND MAGALLANES REGIONS
AS WELL...WITH MAXIMA IN THE ORDER OF 00-05MM/DAY. BY TUESDAY INTO
EARLY WEDNESDAY FOCUS OF PRECIPITATION WILL CONCENTRATE 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 THE MOST REMARKABLE
INGREDIENT FOR HEAVY PRECIPITATION WILL BE STRONG UPPER DYNAMICS.
ALL MODELS ARE AGREEING IN A VERY STRONG UPPER JET DEVELOPING OVER
THE EASTERN PACIFIC. THIS WILL LEAD TO STRONG UPPER DIVERGENCE IN
THE POLAR EXIT OF THE UPPER JET...TO FAVOR HEAVY RAINFALL AMOUNTS
ONCE AGAIN. EXPECTING MAXIMA TO INCREASE TO 25-50MM/DAY.

TO THE EAST OF THE SOUTHERN ANDES IN ARGENTINA...THE LIMITED
AMOUNT OF PRECIPITABLE WATER WILL CONTINUE LIMITING 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. THIS WILL LEAD
TO SCATTERED ACCUMULATIONS OF 05-10MM/DAY WITH ISOLATED HIGHER
AMOUNTS BETWEEN NORTHEASTERN URUGUAY INTO SOUTHERN
BRASIL/NORTHEASTERN ARGENTINA. AS THE FRONT MEANDERS
NORTHEASTWARD...EXPECTING SIMILAR ACCUMULATIONS BETWEEN CENTRAL
PARAGUAY INTO NORTHERN URUGUAY/SOUTHERN BRASIL DURING THURSDAY
INTO EARLY FRIDAY.

TO THE NORTH...COLD FRONT IS RAPIDLY DYING ACROSS NORTHERN
BOLIVIA/SOUTHERN PERU. DURING MONDAY...UPPER LEVEL DIVERGENCE IN
THE TROPICAL ENTRANCE OF AN UPPER JET WILL CONTINUE ENHANCING
CONVECTIVE DEVELOPMENT TO LEAD TO MAXIMA OF 20-40MM/DAY THROUGH
EARLY TUESDAY. AMOUNTS ARE TO DECREASE RAPIDLY AFTERWARDS. OTHER
REGION OF ACTIVITY ALONG THIS WEAK FRONT WILL EXTEND FROM MATO
GROSSO DO SUL INTO SAO PAULO-RIO DO JANEIRO. THROUGH WEDNESDAY
MORNING...SCATTERED CONVECTION WILL LEAD TO SCATTERED AMOUNTS AND
ISOLATED MAXIMA OF 15-30MM/DAY. LIGHTER AMOUNTS ARE EXPECTED OVER
RIO DO JANEIRO WITH MAXIMA LIMITING TO 10MM/DAY.

TRADE WIND SHOWERS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY ALONG THE EASTERN COAST OF BRASIL. EXPECTING SCATTERED
MAXIMA OF 05-10MM/DAY INCREASING TO 10-15MM/DAY AFTER WEDNESDAY
BETWEEN NORTHERN ESPIRITO SANTO SPREADING GRADUALLY INTO
PERNAMBUCO AND RIO GRANDE DO NORTE AS THE WEEKEND APPROACHES.

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





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