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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1834Z Jul 17, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
234 PM EDT THU JUL 17 2014

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

MODEL DISCUSSION (VALID FROM 17 JULY 00UTC): GLOBAL MODELS REMAIN
IN GOOD AGREEMENT THROUGH THE MEDIUM RANGE PERIOD. OUR CONFIDENCE
IN THE FORECAST IS HIGH. SYSTEM OF CONCERN IS A DEEPENING MID
LATITUDE CYCLONE THAT IS TO PROPAGATE ACROSS THE SOUTH ATLANTIC
OVER THE NEXT FEW DAYS. THE STORM IS TO DEEPEN AT A NEARLY
EXPLOSIVE RATE...WITH GLOBAL MODEL GUIDANCE PROJECTING A
METEOROLOGICAL BOMB. THE STRONG CYCLONE IS TO RESULT IN HURRICANE
INTENSITY WINDS.

MID/UPPER LEVEL RIDGE IS TO EXTEND SOUTH ACROSS THE EASTERN
PACIFIC. THIS...IN-TURN...WILL SUSTAIN THE NORTHWARD AMPLIFICATION
OF A TROUGH ALONG THE COAST OF ARGENTINA TO THE SOUTHERN STATES OF
BRASIL. THROUGH 48 HRS THE TROUGH IS TO DEEPEN AT A FAST
PACE...AND A FAIRLY INTENSE MID LEVEL CYCLONE IS TO PERSIST
THROUGH 72-84 HRS...THEN START TO WEAKEN LATER IN THE CYCLE. AT
LOW LEVELS IT IS TO SUSTAIN AN OCCLUDING LOW OFF THE SOUTH COAST
OF BRASIL.  THROUGH 72 HRS THIS LOW IS TO DEEPEN AT A VERY FAST
RATE OF INTENSIFICATION...WITH GLOBAL MODEL GUIDANCE CONSISTENTLY
SHOWING A METEOROLOGICAL BOMB TO THE NORTH OF THE SOUTH GEORGIA
ISLANDS LATER ON FRIDAY/EARLY SATURDAY MORNING. THE DEEPENING MID
LATITUDE CYCLONE WILL THEN INDUCE THE NORTHWARD MIGRATION OF THE
SURFACE FRONT ACROSS THE CONTINENT...WITH FRONT TO PULL ACROSS
SOUTHERN BRASIL-PARAGUAY LATER THIS AFTERNOON. THROUGH 48-60 HRS
THE FRONT IS TO MOVE NORTH ACROSS SAO PAULO TO RIO DE
JANEIRO...TRAILING ACROSS MATO GROSSO TO BOLIVIA. AS THE FRONT
MOVES NORTH ACROSS PARAGUAY TO BOLIVIA IT IS TO TRIGGER SCATTERED
CONVECTION WITH ACCUMULATION OF 20-40MM...TO SPREAD WEST ACROSS
BOLIVIA TO SOUTHERN PERU THROUGH 48-60 HRS. AS THE FRONT STALLS
OVER SOUTHEAST BRASIL...IT IS TO SUSTAIN SCATTERED CONVECTION WITH
ACCUMULATION OF 05-10MM/DAY. THIS WEAKENS THROUGH 72-96 HRS.

MID LEVEL RIDGE PATTERN OVER THE EASTERN PACIFIC IS EXPECTED TO
REMAIN OFF THE COAST OF CHILE THROUGH 48-60 HRS. IT IS TO THEN
RELOCATE ACROSS THE CONTINENT LATER IN THE CYCLE WHILE YIELDING TO
THE NEXT POLAR TROUGH. THE POLAR TROUGH REACHES 100W BY 72
HRS...AND PULLS ACROSS 85W BY 96 HRS...ENTERING CHILE BY 120 HRS.
AS IT ENTERS THE CONTINENT THIS IS TO FAVOR HEIGHT FALLS OF
75-100GPM ON DAY 04...INCREASING TO 120GPM ON DAY 05 WHILE
FOCUSING ACROSS THE CENTRAL PROVINCES IN ARGENTINA.
FURTHERMORE...THE HIGH AMPLITUDE LONG WAVE TROUGH IS TO SUSTAIN A
SUBTROPICAL CONNECTION AS IT MOVES ACROSS THE EASTERN
PACIFIC...ENHANCING MOISTURE TRANSPORT/ CONVERGENCE. AT LOW LEVELS
THE ASSOCIATED FRONT SLIDES UNDER THE RIDGE TO THE EAST AND
NORTH...EXTENDING ACROSS SOUTHERN CHILE TO PATAGONIA IN ARGENTINA
EARLY IN THE CYCLE...WHERE IT IS TO MEANDER THROUGH 96-108 HRS.
THE INFLOW OF SUBTROPICAL MOISTURE WILL COMBINE WITH STRONG
BOUNDARY LAYER WINDS TO SUSTAIN MODERATE TO HEAVY CONVECTION
ACROSS SOUTHERN CHILE. IN THIS AREA EXPECTING MAXIMA OF
20-40MM/DAY THROUGH 60 HRS...AND 15-25MM/DAY AT 60-84 HRS.
SCATTERED CONVECTION IS TO THEN PERSIST THROUGH DAY 05. LATER IN
THE CYCLE THE FRONT IS TO RACE TO NORTHERN ARGENTINA AS A POLAR
RIDGE BUILDS TO THE WEST...REACHING NORTHERN PROVINCES LATER IN
THE CYCLE. AS IT SURGES THE FRONT IS TO TRIGGER
ORGANIZED/POTENTIALLY SEVERE CONVECTION ACROSS RIO DE LA PLATA
BASIN-MESOPOTAMIA VALLEY IN ARGENTINA.

AT 200 HPA...AN ILL ORGANIZED CELL OF THE SUBTROPICAL RIDGE IS TO
CONFINE TO NORTHERN BRASIL/PERU. THE RIDGE ALOFT IS TO VENT
DIURNAL CONVECTION OVER EQUATORIAL SOUTH AMERICA. MOST
ACTIVE...HOWEVER...IS EXPECTED BETWEEN NORTHERN AMAZONAS IN
BRASIL-SOUTHERN COLOMBIA-EASTERN ECUADOR/NORTHERN PERU...WITH
RAINFALL MAXIMA IN THIS AREA TO PEAK AT 15-25MM/DAY. ACROSS
PARA-AMAPA-RORAIMA TO THE EAST... EXPECTING LESSER AMOUNTS...WITH
RAINFALL ACCUMULATION OF 05-10MM/DAY. OVER NORTHEAST
BRASIL...MEANWHILE...A SHEAR LINE IS TO EXTEND TO THE NORTHWEST
ACROSS EASTERN BAHIA/PERNAMBUCO. THIS IS TO ENHANCE LOW LEVEL
CONVERGENCE TO RESULT IN ORGANIZED CONVECTION. EARLY IN THE CYCLE
EXPECTING ACCUMULATION OF 20-45MM. THROUGH 48 HRS THIS DECREASES
TO 20-35MM/DAY...AND LATER IN THE CYCLE IT IS TO PEAK AT 10-15MM.

FERNANDES...INMET (BRASIL)
JALFIN...SMN (ARGENTINA)
DAVISON...WPC (USA)