Prognostic Meteorological Discussion
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931
FXSA20 KWBC 051800
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
100 PM EST FRI FEB 05 2016

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

MODEL DISCUSSION (VALID FROM FEB 05 AT 0000 UTC): FORECAST
CONFIDENCE CONTINUES HIGH THROUGH THE CYCLE. DISCREPANCIES ARISE
ON THE SHORT PERTURBATIONS ESPECIALLY SOUTH OF 45S.

THE SUBTROPICAL UPPER RIDGE/BOLIVIAN HIGH IS FORECAST TO GROW IN
SIZE AND MEANDER TO THE SOUTHEAST. IT IS FORECAST TO EVOLVE FROM A
HIGH OVER SE PERU/BOLIVIA/ACRE EARLY IN THE CYCLE...TO A MASSIVE
RIDGE FROM N CHILE/S BOLIVIA EAST INTO SOUTHERN AND SOUTHEASTERN
BRASIL BY EARLY NEXT WEEK. DEEP-LAYER CONVECTIVE INSTABILITY AND
HIGH VALUES OF PRECIPITABLE WATER ARE PILED UP IN CENTRAL AND SW
PORTIONS OF THE AMAZON BASIN. THIS WILL SUSTAIN A SEASONALLY
ACTIVE PATTERN OF CONVECTION IN N BOLIVIA/E PERU/W BRASIL AND
EASTERN ECUADOR THROUGH THE CYCLE. THROUGH EARLY SATURDAY
EXPECTING LARGEST AMOUNTS ACROSS SE PERU/NORTHERN BOLIVIA WHERE
MAXIMA OF 35-70MM AND THE RISK OF MCS FORMATION ARE BEING
FORECASTED. NORTH ACROSS N PERU/E ECUADOR EXPECTING MAXIMA OF
20-40MM/DAY. BY SATURDAY INTO EARLY SUNDAY EXPECTING MAXIMA OF
30-60MM/DAY ACROSS EASTERN PERU AND ECUADOR INTO W BRASIL. AN
INCREASE IN VENTILATION AND MOISTURE AVAILABILITY WILL INCREASE
MAXIMA ALONG THE EASTERN ANDES OF S PERU AND THE ALTIPLANO TO
15-25MM/DAY. BY SUNDAY INTO EARLY TUESDAY EXPECTING LARGEST
AMOUNTS TO CONCENTRATE ACROSS N PERU/E ECUADOR WHERE EXPECTING
SCATTERED MAXIMA OF 20-40MM/DAY.

DRYING TREND IS EXPECTED IN EASTERN TROPICAL SOUTH AMERICA. THE
CAVADO DO NORDESTE/UPPER TROUGH IS EXPECTED TO SPREAD IN
COMBINATION WITH A SURGE IN THE EASTERLY TRADES. THIS WILL NOT
ONLY ENHANCE UPPER CONVERGENCE BUT THE SURGE WILL ADVECT A STABLE
AND DRIER AIR MASS FROM THE ATLANTIC OCEAN. EXPECTING MAXIMA OF
20-35MM/DAY IN THE AMAZON DELTA EARLY IN THE CYCLE DECREASING
TO10-15MM/DAY BY SUNDAY AND ON. ISOLATED LARGER AMOUNTS ARE
EXPECTED IN STRONGEST THUNDERSTORMS.

ACTIVE PATTERN IS ESTABLISHING IN CENTRAL ARGENTINA UNDER THE
INFLUENCE OF PERSISTENT UPPER TROUGH PATTERN OFF THE COASTS OF
CENTRAL AND SOUTHERN CHILE...AND UNDER THE INFLUENCE OF A
PERSISTENT MOIST TRANSPORT FROM THE NORTH. MODELS ARE SHOWING
PRECIPITABLE WATER VALUES EXCEEDING 50MM EXTENDING AS FAR SOUTH AS
THE RIO DE LA PLATA BASIN ON FRIDAY AND SATURDAY. THIS WILL
PROVIDE THE FUEL FOR STRONG CONVECTION IN THE REGION.
INITIALLY...EXPECTING MAXIMA OF 25-50MM/DAY WITH THE RISK OF
SEVERE CONVECTION EXTENDING FROM CUYO INTO NORTHERN PATAGONIA AND
THE BUENOS AIRES PROVINCE...AIDED BY LOW-LEVEL CONVERGENCE IN THE
MOUTH OF AN EASTERLY LOW-LEVEL JET IN NORTHERN PATAGONIA. DIURNAL
CONVECTION IN THE ANDES OF NW ARGENTINA IS TO ALSO PRODUCE MAXIMA
OF 25-50MM/DAY. BY SATURDAY INTO SUNDAY EXPECTING AN INCREASE IN
ACCUMULATIONS TO MAXIMA OF 30-60MM/DAY FROM TUCUMAN/SALTA SE INTO
THE BUENOS AIRES PROVINCE/LA PAMPA. BY SUNDAY INTO EARLY MONDAY
EXPECTING A PEAK IN ACTIVITY. STRONG THUNDERSTORMS ARE TO STRETCH
FROM CORDOBA SW INTO THE RIO DE LA PLATA BASIN WITH THE RISK OF
MCS CONVECTION. SIMILAR CONDITIONS ARE EXPECTED ON MONDAY INTO
EARLY TUESDAY FROM SANTIAGO DEL ESTERO/N CORDOBA SE INTO ENTRE
RIOS AND URUGUAY/RIO DE LA PLATA.

LOPEZ...SMN (ARGENTINA)
GALVEZ/DAVISON...WPC (USA)

$$





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