692
FXSA20 KWBC 081616
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1216 PM EDT MON SEP 08 2008
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
MODEL COMPARISON (VALID FROM 00Z SEP 08). SUBTLE DIFFERENCES
SEPARATE THE MODELS THROUGH DAY 05...AS THEY GENERALLY AGREE ON
THE LONG WAVE PATTERN EVOLUTION. THE NCEP AND EUROPEAN ENSEMBLES
CLUSTER IN SUPPORT OF THE DETERMINISTIC SOLUTION...WHILE THE
CANADIAN ENSEMBLES TEND TO DIVERGE/SHOW MORE VARIABILITY.
AT MID LEVELS...A BROAD/LOW AMPLITUDE TROUGH IS TO DOMINATE THE
SOUTHERN CONE OVER THE NEXT FEW DAYS. EMBEDDED IN THIS FLOW...A
SHORT WAVE TROUGH WILL MOVE ALONG 85W/90W BY 24 HRS...AND THROUGH
72 HRS THE TROUGH IS TO CONTINUE EAST ACROSS 70W. BY 96 HRS THE
TROUGH WILL MOVE ALONG 60W/64W...WITH A LOW TO CLOSE NEAR 40S
60W. THIS AXIS IS TO MOVE ALONG 50W TO SOUTHERN BRASIL BY 120
HRS. AS IT ENTERS THE SOUTHERN CONE BETWEEN 48-72 HRS...THIS
SYSTEM WILL SUPPORT/INDUCE HEIGHT FALLS OF 25-50GPM. BUT AS IT
MOVES ACROSS BUENOS AIRES PROVINCE/URUGUAY ON DAY 04...AND AS A
RESULT OF THE RAPID INTENSIFICATION OF THIS VORTEX...HEIGHT FALLS
ARE FORECAST TO INCREASE TO 75-150GPM. AT LOW LEVELS A POLAR
FRONT EXTENDS ACROSS SOUTHEAST BRASIL-MATO GROSSO TO RONDONIA/
NORTHERN BOLIVIA. THIS FRONT IS TO RETROGRESS ACROSS PARAGUAY TO
ALIGN ACROSS RIO GRANDE DO SUL-CHACO ARGENTINO-JUJUY/ SALTA BY 42
HRS...WHERE IT WILL THEN REMAIN THROUGH 84 HRS. THIS WILL FAVOR
SCATTERED CONVECTION ACROSS SOUTHERN BRASIL-SAO PAULO...WITH
DAILY RAINFALL AMOUNTS OF 15-25MM. THIS WILL PERSIST THROUGH 48
HRS...WITH A SURGE IN ACTIVITY BY 72-84 HRS...WHEN MAXIMA ALONG
THE STATIONARY FRONT IS TO PEAK AT 20-40MM.
SIMULTANEOUSLY...ANOTHER FRONT ENTERS SOUTHERN CHILE BY 24-30
HRS...TO MOVE ACROSS PATAGONIA THROUGH 48-60 HRS. BY 72-96 HRS
THE FRONT WILL UNDULATE NORTH ACROSS BUENOS AIRES PROVINCE-
CORDOBA IN ARGENTINA. BETWEEN 84-96 HRS IT WILL MERGE
WITH/REINFORCE THE OLD FRONT OVER SOUTHERN BRASIL-NORTHERN
ARGENTINA. AS THEY COMBINE...AND A LOW OCCLUDES OFF THE SOUTHERN
COAST OF BRASIL...THE FRONT WILL THEN RACE NORTH INTO SOUTHEAST
BRASIL-MATO GROSSO DO SUL-NORTHERN BOLIVIA. AS THE FRONT ENTERS
SOUTHERN CHILE IT WILL FAVOR SCATTERED RAINFALL WITH ACCUMULATION
OF 10-20MM. OVER SOUTHERN BRASIL-MESOPOTAMIA VALLEY-SOUTHEAST
PARAGUAY MAXIMA WILL PEAK AT 20-40MM...WITH LOCALLY HIGHER
AMOUNTS POSSIBLE. NOTE SLIGHT RISK OF SEVERE CONVECTION ON DAY
04...WHEN FAVORABLE JET DYNAMICS AND MID LEVEL COLD AIR INCURSION
WILL DESTABILIZE THE AIR MASS.
THE NEXT MID LEVEL TROUGH IS TO MOVE ACROSS 120W AND SOUTH OF 35S
BY 48 HRS. THROUGH 72 HRS IT WILL MOVE ACROSS 100W/110W...
MEANWHILE PUSHING AGAINST AN INDUCED RIDGE OFF THE COAST OF
CHILE. THROUGH 120 HRS THE TROUGH WILL MOVE ALONG 85W/90W...WITH
SHORT WAVE ENERGY FOCUSING OVER CHILE SOUTH OF 34S. THE
ASSOCIATED FRONT WILL ENTER EXTREME SOUTHERN CHILE BY 96-108
HRS...WHERE IT WILL MEANDER THROUGH 108-120 HRS. AS IT ENTERS
SOUTHERN CHILE IT WILL SUSTAIN RAINFALL MAXIMA OF 15-24MM/DAY.
AT 200 HPA...A DISORGANIZED SUBTROPICAL RIDGE WILL REMAIN OVER
NORTHERN SOUTH AMERICA. THIS IS TO GRADUALLY ALLOW FOR THE
NORTHWARD AMPLIFICATION OF A TROUGH ACROSS BRASIL ALONG 48W-50W
BY MID CYCLE...WITH TROUGH PATTERN TO PERSIST THROUGH 120 HRS.
SCATTERED CONVECTION OVER NORTHWEST BRASIL-NORTHERN PERU/SOUTHERN
COLOMBIA WILL PERSIST THROUGH 84-96 HRS...WITH DAILY MAXIMA OF
15-30MM. LOCALLY HIGHER AMOUNTS ARE POSSIBLE OVER NORTHERN PERU
THROUGH 36-48 HRS WITH MAXIMA OF 20-40MM.
GUZMAN...SENAMHI (BOLIVIA)
URRA...DMC (CHILE)
DAVISON...HPC (USA)
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