Prognostic Meteorological Discussion
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FXSA20 KWBC 261540
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1139 AM EDT TUE MAY 26 2015

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

MODEL DISCUSSION (VALID FROM MAY 26 AT 0000 UTC): CONFIDENCE IN
THE FORECAST IS HIGH THROUGH 108 HRS...WITH DETERMINISTIC GLOBAL
MODELS AND ENSEMBLE MEMBERS CONVERGING ON A SIMILAR SOLUTION INTO
THE MEDIUM RANGE PERIOD.

THE SYSTEM OF CONCERN IS A DEEPENING MID LEVEL TROUGH THAT PULLS
ACROSS MID SECTIONS OF SOUTH AMERICA OVER THE NEXT THREE DAYS.
THIS IS TO SPILL ACROSS THE NORTHERN ANDES OF CHILE LATER THIS
EVENING...MEANWHILE FAVORING HEIGHT FALLS OF 50-75GPM ACROSS
PARAGUAY-MESOPOTAMIA VALLEY/SOUTHERN STATES OF BRASIL. THROUGH 72
HRS THE TROUGH IS TO SLOWLY PULL ACROSS SOUTHERN BRASIL...TO
MEANDER INTO THE  ATLANTIC BY 96-108 HRS. AS IT MEANDERS ACROSS
MID SECTIONS OF SOUTH AMERICA THIS IS TO INTERACT WITH A SURFACE
FRONT OVER SOUTHERN BRASIL-PARAGUAY...TRIGGERING CYCLOGENESIS
ALONG THE SURFACE FRONT. THE LOW IS TO GRADUALLY DEEPEN THROUGH
54-60 HRS...AND IT IS LIKELY TO OCCLUDE AS IT MOVES ACROSS
SOUTHERN BRASIL TO THE WESTERN ATLANTIC. THE DEEPENING LOW IS TO
SUSTAIN A SOUTHERLY LOW LEVEL JET ACROSS NORTHWEST
ARGENTINA/BOLIVIA...DRIVING THE SURFACE FRONT NORTH ACROSS
SOUTHERN BRASIL-MATO GROSSO DO SUL TO NORTHERN BOLIVIA BY 48 HRS.
IT IS TO THEN MEANDER NORTH INTO SAO PAULO BY 72-96 HRS. ACROSS
PARAGUAY-MESOPOTAMIA VALLEY IN ARGENTINA THIS IS TO TRIGGER AN MCS
WITH ORGANIZED DEEP CONVECTION TO FAVOR RAINFALL MAXIMA OF
100-150MM. LOCALLY HIGHER AMOUNTS ARE HIGHLY LIKELY. ON THE
SOUTHERN STATES OF BRASIL THIS IS TO THEN FAVOR RAINFALL MAXIMA OF
75-125MM...WITH MOST INTENSE EXPECTED THROUGH 54/60 HRS. ACROSS
BOLIVIA-RONDONIA/ACRE TO SOUTHERN BRASIL THE SOUTHERLY WIND SURGE
IS TO TRIGGER MODERATE TO HEAVY CONVECTION BY 36-60 HRS...WITH
MAXIMA OF 20-45MM. THIS IS TO SPREAD NORTH ACROSS CENTRAL JUNGLE
TO NORTHERN PERU/SOUTHERN COLOMBIA BY 72-96 HRS...WHERE MAXIMA IS
TO PEAK AT 25-50MM.

A HIGH AMPLITUDE MID/UPPER LEVEL TROUGH IS TO THEN MIGRATE ACROSS
THE EASTERN PACIFIC TO SOUTHERN/CENTRAL PORTIONS OF CHILE BY 54-60
HRS...TO THEN DRIFT EAST ACROSS THE SOUTHERN CONE TO THE WESTERN
ATLANTIC BY 96-108 HRS. AT LOW LEVELS THE HIGH AMPLITUDE TROUGH IS
TO SUSTAIN A BROAD TROUGH ACROSS THE FAR EASTERN PACIFIC TO
SOUTHERN PORTIONS OF CHILE LATER ON DAY 02...THAT IS TO ALSO MOVE
EAST ACROSS THE SOUTHERN CONE THROUGH 72-84 HRS. FURTHERMORE...THE
HIGH AMPLITUDE/LONG WAVE TROUGH PATTERN IS TO SUSTAIN A
SUBTROPICAL CONNECTION AS IT ENTERS THE SOUTHERN PORTIONS OF
CHILE. THIS IS TO FEED ORGANIZED CONVECTION BETWEEN TEMUCO-ISLA DE
CHILOE...WHERE WE EXPECT RAINFALL MAXIMA OF 20-40MM BY 48-72 HRS.
OVER TIERRA DEL FUEGO/EXTREME SOUTHERN PORTIONS OF CHILE THE
RAINFALL MAXIMA IS TO PEAK AT 05-10MM.

NORTH OVER THE CONTINENT...AT 200 HPA...A BROAD CELL OF THE
SUBTROPICAL RIDGE IS TO DOMINATE PERU/EASTERN TROPICAL PACIFIC
WHILE CENTERING ON A CLOSED HIGH OVER NORTHERN PERU. THROUGH 48
HRS THE HIGH IS TO MEANDER WEST INTO THE EASTERN TROPICAL PACIFIC.
AS IT MEANDERS OVER NORTHWEST SOUTH AMERICA...THE BROAD RIDGE IS
TO INDUCE THE NORTHWARD AMPLIFICATION OF A TROUGH ACROSS PARA IN
BRASIL TO THE GUIANAS. THIS TROUGH IS TO PERSIST THROUGH 72 HRS.
THE AMPLIFYING TROUGH IS TO ENHANCE DIURNAL CONVECTION ACROSS THE
AMAZON RIVER DELTA REGION-NORTHERN PARA IN BRASIL...WHERE WE
EXPECT MAXIMA OF 20-45MM THROUGH 48-60 HRS. THIS THEN DECREASES
LATER IN THE CYCLE. ACROSS RORAIMA/NORTHERN AMAZONAS THE DAILY
MAXIMA IS TO PEAK AT 20-30MM OVER THE NEXT FEW DAYS.

CHARPENTIER...DMC (CHILE)
SCHNEIDER...INMET (BRASIL)
UNSIHUAY...UNALM (PERU)
GALVEZ...WPC (USA)
$$





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