162
FXSA20 KWBC 182018
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
318 PM EST TUE FEB 18 2025
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICA FORECAST BULLETIN 18 FEB 2025 2030UTC:
ON THE CLIMATE SCALE...
THE MADDEN JULIAN OSCILLATION (MJO) HAS BECOME DISORGANIZED, WITH
MODELS INDICATING THAT SOME UPPER LEVEL DIVERGENCE IS STILL
PRESENT OVER THE EAST PACIFIC AND WILL LIKELY RETROGRADE WEST.
ALTHOUGH UNCERTAINTY REMAINS IN THE PROPAGATION OF THE MJO, EXPECT
A GENERAL CONVERGENT PHASE.
IN MID - LATITUDE SOUTH AMERICA...
IN CHILE, A SERIES OF UPPER TO MID LEVEL TROUGHS WILL CONTINUE TO
MIGRATE ACROSS CENTRAL CHILE THROUGH THE NEXT THREE DAYS. FROM
MONDAY THROUGH TUESDAY MORNING, A POTENT JET STREAK WILL TRAVERSE
ACROSS SOUTHERN CHILE, FAVORING UPPER DIVERGENCE. THEREAFTER,
UPPER DIVERGENCE WILL BE SUSTAINED BY AN AMPLIFYING UPPER TROUGH,
WHICH WILL IMPACT THE REGION AFTER WEDNESDAY MORNING. AT THE LOWER
LEVELS, A LONG FETCH MOISTURE TONGUE ACCOMPANIED BY STRONG WINDS
WILL ENHANCE OROGRAPHIC EFFECTS ACROSS SOUTH-CENTRAL CHILE
STARTING MONDAY THROUGH WEDNESDAY. THOUGH THE WIND DIRECTION IS
EXPECTED TO SHIFT TO A MORE NORTHERLY COMPONENT BY WEDNESDAY
EVENING, INCREASING WIND SPEEDS DURING THIS TIME WILL CONTINUE TO
FAVOR MOISTURE CONVERGENCE ACROSS CENTRAL CHILE. FROM MONDAY
MORNING THROUGH TUESDAY MORNING, EXPECT A MAXIMUM PRECIPITATION
TOTAL OF 15 - 30MM AND INCREASING TO 20 - 40MM/DAY FOR TUESDAY AND
WEDNESDAY. NOTE, AFTER THURSDAY MORNING, ANOTHER UPPER TROUGH,
ENHANCED MID-LEVEL VORTICITY ADVECTION, INCREASING WIND SPEEDS,
LOW LEVEL WIND SPEEDS, AND A LONG FETCH MOISTURE TONGUE MAY FAVOR
HIGHER PRECIPITATION TOTALS THROUGH THE DAY.
IN TROPICAL SOUTH AMERICA...
IN THE UPPER LEVELS, THE BOLIVIAN HIGH, CENTERED AT 21S 77W MONDAY
AFTERNOON, WILL CONTINUE TO DRIVE UPPER DIVERGENCE ACROSS ITS
PERIPHERY. TO THE EAST, AN UPPER TROUGH HAS DEVELOPED ACROSS
CENTRAL BRASIL, CENTERED AT 13S 52W MONDAY AFTERNOON. BY MID-WEEK,
THIS TROUGH IS ANTICIPATED TO LOSE ITS STRUCTURE.
A STATIONARY FRONT WILL BE LOCATED ACROSS SOUTH BRASIL INTO NORTH
PARAGUAY BY MONDAY EVENING AND WEAKENING INTO A TROUGH THEREAFTER.
IN THE UPPER LEVELS, AN UPPER TROUGH ACCOMPANIED BY SPEED
DIVERGENCE WILL HELP ENHANCE ASCENT IN THIS REGION. THIS UPPER
TROUGH WILL REMAIN SEMI-STATIONARY ACROSS THIS REGION THROUGH
THURSDAY EVENING AND WILL ASSIST IN WEAKENING THE STRUCTURE OF THE
AFOREMENTIONED UPPER TROUGH ACROSS CENTRAL BRASIL. IN THE LOW
LEVELS, MOISTURE CONVERGENCE WILL ALSO BE MORE FAVORABLE THROUGH
MONDAY EVENING, WHICH WILL YIELD A TOTAL PRECIPITATION MAXIMA OF
35 - 70MM ACROSS SOUTH BOLIVIA, NORTH PARAGUAY, AND SOUTH BRASIL
FROM MONDAY MORNING THROUGH TUESDAY MORNING. NOTE, A DEVELOPING
LOW PRESSURE SYSTEM OFF THE COAST OF SOUTHEAST BRASIL WILL HELP
INCREASE PRECIPITATION ACCUMULATIONS FROM MONDAY MORNING THROUGH
TUESDAY MORNING IN THIS REGION AND IS EXPECTED TO PROPAGATE OUT TO
SEA AFTER TUESDAY MORNING. FROM TUESDAY MORNING THROUGH WEDNESDAY
MORNING, A TOTAL PRECIPITATION MAXIMUM OF 20 - 45MM IS POSSIBLE
ACROSS NORTH PARAGUAY, WHERE A MID - LEVEL TROUGH, ACCOMPANIED BY
VORTICITY ADVECTION, AND LOW LEVEL MOISTURE CONVERGENCE WILL MOVE
ACROSS THIS REGION.
ELSEWHERE IN TROPICAL SOUTH AMERICA, A SERIES OF SURFACE TROUGHS
WILL CONTINUE TO MOVE ACROSS NORTH SOUTH AMERICA, WHERE MOISTURE
CONVERGENCE WILL PERSIST. EXPECT THE HIGHEST TOTAL PRECIPITATION
MAXIMA TO OCCUR FOR MONDAY MORNING THROUGH TUESDAY MORNING AND
DECREASE THEREAFTER AS LOW LEVEL MOISTURE AND UPPER DIVERGENCE
DECREASE IN PARTS OF THE REGION. ELSEWHERE, EXPECT AN ENHANCEMENT
IN DIURNAL CONVECTION ALONG THE ITCZ / NET / SOUTHERN ITCZ.
REGIONS OF INTEREST INCLUDE THE AMAZON DELTA, WHERE EXPECT DAILY
MAXIMA PRECIPITATION TOTALS OF 20 - 45MM/DAY, AND NORTHEAST
BRASIL, WHERE EXPECT TOTALS OF 20 - 35MM/DAY. IN ECUADOR, EXPECT
DAILY MAXIMA PRECIPITATION TOTALS OF 30 - 60MM/DAY, ENHANCED BY
OROGRAPHIC EFFECTS AND INCREASED MOISTURE CONVERGENCE. IN EAST
PERU, THE DAY OF GREATEST PRECIPITATION IMPACT WILL BE FROM MONDAY
MORNING THROUGH TUESDAY MORNING, WHEN MOISTURE CONVERGENCE AND
UPPER DIVERGENCE WILL BE MOST FAVORABLE. EXPECT DECREASING MAXIMA
PRECIPITATION TOTALS FROM TUESDAY TO THURSDAY MORNING.
MORALES...(WPC)
CASTELLANOS...(WPC)
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