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000
FXSA20 KWBC 191524
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1124 AM EDT WED JUN 19 2013

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

MODEL COMPARISON (VALID FROM 00 UTC JUNE 19): CONSISTENT WITH
PREVIOUS FORECASTS WE EXPECT POLAR TROUGH ENTERING THE DRAKE
PASSAGE ON DAY 02 TO RAPIDLY INTENSIFY AS IT NEARS TIERRA DEL
FUEGO. MODELS CONTINUE TO PROJECT AN EXPLOSIVE RATE OF
INTENSIFICATION...WITH SYSTEM DEEPENING FROM A 972 HPA LOW AT 36
HRS TO A 928 HPA LOW BY 60 HRS. THE ENSUING METEOROLOGICAL BOMB
WILL SUSTAIN HURRICANE INTENSITY WINDS ACROSS THE SOUTHERN CONE
AND HEAVY PRECIPITATION AMOUNTS. THE WORST WILL FOCUS ON EXTREME
SOUTHERN PORTIONS OF TIERRA DEL FUEGO. CONFIDENCE IN THIS FORECAST
IS HIGH.

POLAR TROUGH IS INITIALIZED OVER THE WESTERN ATLANTIC WITH AXIS
NORTH ALONG THE COAST OF ARGENTINA TO THE BUENOS AIRES PROVINCE.
THROUGH 24 HRS THE 500 HPA TROUGH WILL PULL ACROSS 40W...NEARING
20W/25W BY 48 HRS. A SHORT WAVE TROUGH ON THE NORTHERN STREAM
TRAILS THIS AXIS...WITH SHORT WAVE PERTURBATION MEANDERING OFF THE
CENTRAL/NORTHERN COAST OF CHILE. AT 30-36 HRS THE TROUGH WILL
SPILL ACROSS THE NORTHERN ANDES TO NORTHWEST ARGENTINA...AND
THROUGH 60-72 HRS IT ACCELERATES ACROSS SOUTHERN BRASIL TO THE
WESTERN ATLANTIC. IT IS TO THEN GRADUALLY MERGE INTO THE SYNOPTIC
FLOW AS IT MEANDERS EAST ACROSS THE SOUTH ATLANTIC. AT LOW
LEVELS...THE POLAR TROUGH SUSTAINS A SURFACE FRONT ACROSS SOUTHERN
BRASIL TO NORTHERN ARGENTINA. THROUGH 24 HRS...UNDER INFLUENCE OF
A 1027-1029 HPA POLAR HIGH OVER ARGENTINA...THE FRONT WILL
UNDULATE NORTH ACROSS SANTA CATARINA-MATO GROSSO DO SUL IN BRASIL
TO CENTRAL BOLIVIA...WHERE IT IS FORECAST TO STALL. THE NORTHERN
STREAM PERTURBATION...AS IT SPILLS ACROSS THE ANDES...IS TO THEN
INTERACT WITH THE MEANDERING FRONT...TO INDUCE A FRONTAL WAVE OVER
SOUTHERN BRASIL BY 48-60 HRS. THE LOW IS FORECAST TO QUICKLY
DEEPEN THROUGH 60-72 HRS AS IT MOVES OFF THE SOUTHERN COAST OF
BRASIL. ALONG THE TAIL END OF THE FRONT...AS IT MEANDERS OVER
BOLIVIA-SOUTHERN JUNGLE OF PERU...EXPECTING SCATTERED DEEP
CONVECTION EARLY IN THE CYCLE TO RESULT IN RAINFALL AMOUNTS OF
25-50MM. THROUGH 36-60 HRS THIS WILL DECREASE TO 15-20MM...AND BY
60-96 HRS EXPECT RAINFALL AMOUNTS OF 10-15MM/DAY. ACROSS MATO
GROSSO DO SUL-SAO PAULO-SANTA CATARINA...THE ENSUING FRONTAL WAVE
WILL SUSTAIN RAINFALL MAXIMA OF 25-50MM...WITH MOST INTENSE
EXPECTED BETWEEN 24-48 HRS. THIS THEN DECREASES TO 15-25MM BY
72-84 HRS.

A BROAD MID/UPPER LEVEL RIDGE IS TO DOMINATE UPSTREAM FLOW ACROSS
THE EASTERN PACIFIC...WITH AXIS TO ENVELOP AREA BETWEEN 110W-90W
AND TO THE NORTH 60S. RIDGE PATTERN IS REACH MAXIMUM AMPLITUDE ON
DAYS 03-04. THIS WILL REFLECT AT LOW LEVELS OF THE
ATMOSPHERE...WITH BROAD RIDGE TO DOMINATE THE NORTHERN AND
SOUTHERN STREAM ACROSS THE FAR EASTERN PACIFIC. A 1031 HPA HIGH IS
TO ANCHOR THIS RIDGE...WITH CENTER TO INTENSIFY TO A 1035 HPA HIGH
LATER IN THE CYCLE.

AS THE MID/UPPER LEVEL RIDGE HOLDS OVER THE EASTERN PACIFIC...IT
WILL SUSTAIN A TIGHT BELT OF MID LATITUDE WESTERLIES ACROSS THE
SOUTHEAST PACIFIC TO THE SOUTHERN CONE. EMBEDDED IN THIS
FLOW...THE GLOBAL MODELS FORECAST A SHORT WAVE TROUGH ON THE
SOUTHERN STREAM TO RAPIDLY PROPAGATE UNDER THIS AXIS. THROUGH 24
HRS THE TROUGH WILL PULL ACROSS 90W/95W AND TO THE SOUTH OF 50S.
AS IT ENTERS THE DRAKE PASSAGE/SOUTHERN CONE BY 36-42 HRS...UNDER
COUPLED JETS/STRONG DIVERGENCE ALOFT...THIS SYSTEM IS FORECAST TO
RAPIDLY INTENSIFY. BETWEEN 36-60 HRS...THE DEEPENING MID LEVEL
TROUGH WILL SUSTAIN HEIGHT FALLS OF 250-300GPM. BY 72-96 HRS...AS
THE TROUGH MVOES TO THE WESTERN ATLANTIC...THIS IS TO THEN EVOLVE
INTO A HIGHLY AMPLIFIED LONG WAVE TROUGH. THIS IS TO ALSO SUSTAIN
A SHORT WAVE TROUGH ON THE NORTHERN STREAM THAT LIFTS TO CENTRAL
CHILE BY 96-108 HRS...WHERE IT IS TO THEN MEANDER THROUGH 120-132
HRS...WITH ASSOCIATED SHORT WAVE ENERGY FOCUSING ACROSS
CENTRAL/NORTHERN CHILE. AT LOW LEVELS THIS WILL SUSTAIN A
DEEPENING SURFACE LOW THAT TRACKS JUST SOUTH OF TIERRA DEL FUEGO
BY 36-42 HRS. THROUGH 60 HRS THIS IS TO RAPIDLY INTENSIFY...WITH
CENTRAL PRESSURE TO DECREASE FROM 972 TO A 928 HPA LOW DURING THAT
PERIOD. THE RAPID RATE OF INTENSIFICATION WILL THEN RESULT IN
STRONG BOUNDARY LAYER WINDS ACROSS TIERRA DEL FUEGO TO THE
SOUTHERN CONE...WITH 850 HPA WINDS TO PEAK AT 65-70KT. THE
ASSOCIATED SURFACE FRONT PULLS ACROSS SOUTHERN CHILE TO PATAGONIA
THROUGH 48 HRS...INTO THE BUENOS AIRES PROVINCE/RIO DE LA PLATA
BASIN-CENTRAL CHILE BY 96 HRS. ACROSS TIERRA DEL FUEGO/SOUTHERN
CHILE THIS WILL SUSTAIN HEAVY PRECIPITATION AMOUNTS  ON DAYS
01-02. ON DAY 01 EXPECTING RAINFALL AMOUNTS OF 20-35MM...WHILE ON
DAY 02...IN MOSTLY SOLID PRECIPITATION...EXPECTING SNOWFALL
AMOUNTS OF 25-50CM. AS THE FRONT LIFTS NORTH ACROSS SOUTHERN
CHILE...IT IS TO SUSTAIN RAINFALL AMOUNTS OF 15-20MM OVER
TEMUCO-PUERTO MONTT...WITH ACTIVITY TO SPREAD NORTH ACROSS
CONCEPCION ON DAY 03.

NORTH OVER THE CONTINENT...AT 200 HPA...A BROAD CELL OF THE
SUBTROPICAL RIDGE IS TO BUILD ACROSS BRASIL THROUGH 36-48
HRS...WITH A BROAD RIDGE TO THEN PERSIST ACROSS THE CONTINENT TO
THE NORTH OF 20S THROUGH 120-132 HRS. THE INTENSIFICATION OF THE
SUBTROPICAL RIDGE IS IN RESPONSE TO EVOLVING LONG WAVE POLAR
TROUGH PATTERN TO THE SOUTH. RIDGE ALOFT...MEANWHILE...IS TO VENT
DEEP CONVECTION ACROSS NORTHERN PERU-SOUTHERN COLOMBIA-ECUADOR TO
AMAZONAS IN BRASIL. IN THIS AREA EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY IN SCATTERED CONVECTION. MOST ACTIVE OVER THE NEXT TWO
DAYS. CONVECTION IS TO THEN FLARE UP ACROSS EQUATORIAL SOUTH
AMERICA LATER IN THE CYCLE.

OLIVARES...SENAMHI (PERU)
SILVA DE SOUZA...INMET (BRASIL)
DAVISON...WPC (USA)
$$