Prognostic Meteorological Discussion
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000
FXSA20 KWBC 171615
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1114 AM EST TUE JAN 17 2017

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

MODEL DISCUSSION (VALID FROM JANUARY 17 AT 0000 UTC): IN A TIGHT
BELT OF MID LATITUDE WESTERLIES...PROGRESSIVE MID LEVEL SHORT WAVE
TROUGHS ARE TO STREAM ACROSS THE SOUTHEAST PACIFIC AND THE
SOUTHERN CONE OF SOUTH AMERICA. THIS PATTERN IS TO HOLD NEARLY
UNCHANGED DURING THE NEXT 48-60 HRS. AT LOW LEVELS...THIS IS TO
SUSTAIN AN ELONGATED FRONT THAT IS TO EXTENDS ACROSS THE SOUTHERN
CONE OF SOUTH AMERICA TO THE SOUTHEAST PACIFIC. THE ELONGATED
FRONT WILL ENHANCE MOISTURE CONVERGENCE TO THE SOUTH OF
44S...FAVORING SCATTERED CONVECTION WITH ACCUMULATION OF
05-10MM/DAY OVER THE NEXT COUPLE OF DAYS.

LATER ON THURSDAY...AS A MID LEVEL RIDGE BUILDS TO THE WEST
BETWEEN 160W-130W...A TROUGH IS TO DEEPEN/AMPLIFY ACROSS THE
SOUTHEAST PACIFIC. THE DEEPENING TROUGH WILL THEN PRESS AGAINST A
BROAD CELL OF THE SUBTROPICAL RIDGE TO THE NORTH. THIS IS TO
TIGHTEN THE GRADIENT ACROSS THE SOUTHERN CONE...WITH SHORT WAVE
ENERGY TO GRADUALLY SHEAR ACROSS CHILE TO THE SOUTH OF TEMUCO. AT
LOW LEVELS...THE DEEPENING TROUGH WILL SUSTAIN A DEEP OCCLUSION
ACROSS THE BELLINGSHAUSEN SEA AND A BROAD TROUGH OFF THE SOUTH
COAST OF CHILE. THROUGH FRIDAY EVENING THIS IS TO SLOWLY MOVE TO
THE EAST-SOUTHEAST ACROSS THE DRAKE PASSAGE/ANTARCTIC PENINSULA TO
THE WEDDELL SEA. ASSOCIATED POLAR FRONT ENTERS SOUTHERN CHILE
LATER ON THURSDAY...TO THEN PULL ACROSS PATAGONIA TO THE WESTERN
ATLANTIC LATER ON FRIDAY. THIS IS TO ALSO FAVOR SCATTERED
CONVECTION ACROSS SOUTHERN PORTIONS OF CHILE WITH ACCUMULATION OF
05-10MM/DAY.

BROAD CELL OF THE SUBTROPICAL RIDGE TO THE NORTH IS TO ANCHOR ON A
CLOSED HIGH OFF THE NORTH COAST OF CHILE. THE BROAD RIDGE IS TO
HOLD DURING THE NEXT FIVE DAYS. AS IT BRANCHES ACROSS NORTHERN
CHILE TO CENTRAL/NORTHERN ARGENTINA THE MID LEVEL RIDGE PATTERN
WILL SUSTAIN A CAP INVERSION ACROSS MID SECTIONS OF SOUTH AMERICA.
AS IT HOLDS...THE RIDGE WILL FAVOR THE NORTHWARD AMPLIFICATION OF
A TROUGH ACROSS SOUTHERN BRASIL TO MATO GROSSO DO SUL. THIS WILL
COMBINE WITH A SURFACE TROUGH OVER SOUTHEAST BRASIL TO FAVOR
ORGANIZED DEEP CONVECTION ACROSS SAO PAULO-MINAS
GERAIS-TOCANTINS/GOIAS IN EASTERN BRASIL. IN THIS AREA INITIALLY
EXPECTING RAINFALL AMOUNTS OF 25-50MM. THROUGH FRIDAY MORNING IT
WILL INCREASE TO 40-80MM WITH MOST ACTIVE EXPECTED OVER SAO PAULO
AND RIO DE JANEIRO.

AT 200 HPA...THIS WILL REFLECT AS A BROAD RIDGE OVER
CENTRAL/NORTHERN SOUTH AMERICA. A TROUGH...MEANWHILE...WILL LIE TO
THE EAST ACROSS THE NORTHEAST STATES OF BRASIL. THE FLOW IS TO
DIVERGE BETWEEN THE RIDGE TO THE WEST AND THE TROUGH TO THE
EAST...FAVORING A SURGE IN ACTIVITY ACROSS EQUATORIAL SOUTH
AMERICA. ACROSS PARA-AMAZONAS IN BRASIL THE MAXIMA IS TO PEAK AT
75-125MM OVER THE NEXT THREE DAYS...AND 25-50MM LATER IN THE WEEK.
THIS IS TO ALSO VENT CONVECTION ON THE SIERRA AND JUNGLE OF PERU
AND BOLIVIA. ON THE SIERRA THE MAXIMA WILL PEAK AT
15-20MM/DAY...WHILE OVER THE JUNGLE INITIALLY EXPECTING RAINFALL
AMOUNTS OF 20-35MM. THROUGH THURSDAY THIS WILL INCREASE TO 20-45MM
WHILE BUILDING NORTH ACROSS NORTHERN JUNGLE OF PERU TO EASTERN
ECUADOR/SOUTHERN COLOMBIA.

DURAN...SMN (ARGENTINA)
TEPES...DMC (CHILE)
DAVISON/GALVEZ...WPC (USA)
$$




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