Prognostic Meteorological Discussion
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000
FXSA20 KWBC 031811
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
210 PM EDT MON AUG 03 2015

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

NOTE: HEAVY RAINFALL EVENT TO DEVELOP ACROSS CENTRAL CHILE DURING
LATE WEDNESDAY TO PEAK THURSDAY AND WANE DURING FRIDAY.
PRELIMINARY ANALYSIS SUGGESTS POTENTIAL RAINFALL AMOUNTS AS HIGH
AS 100-150MM/EVENT IN COASTAL AREAS OF THE VALPARAISO REGION
(QUINTA REGION)...MAXIMA OF 50-75MM/EVENT IN THE SANTIAGO
VALLEY...MAXIMA OF 50-100MM/EVENT IN INTERIOR REGIONS OF THE BIO
BIO...MAULE AND OHIGGINS REGIONS...AND MAXIMA OF 20-40MM/EVENT IN
THE COQUIMBO REGION.

MODEL DISCUSSION (VALID FROM AUG 03 AT 0000 UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS ARE IN GENERALLY GOOD AGREEMENT THROUGH
108-120 HRS AS THEY INDICATE AN EVOLUTION INTO A VERY AMPLIFIED
LONG WAVE PATTERN ACROSS SOUTH AMERICA. DISCREPANCIES IN THE
EVOLUTION OF EMBEDDED SHORT WAVE ARISE HOWEVER AS EARLY AS 84-96
HRS. THIS COMPROMISES THE FORECAST OF THE EXACT LOCATION OF LATE
CYCLE ACTIVITY ACROSS MOST OF ARGENTINA.

MODELS AND ENSEMBLE EMBERS SUGGEST A SIGNIFICANT CHANGE OF PATTERN
IN SOUTH AMERICA AS THEY ALL SHOW A TRANSITION INTO A HIGHLY
AMPLIFIED AND SLOW-PROGRESSING LONG WAVE PATTERN INTO THE
WEEKEND...WITH A LARGE TROUGH DOMINATING CHILE AND THE EASTERN
PACIFIC AND A RIDGE TO THE EAST FROM BOLIVIA/PARAGUAY INTO
URUGUAY/SOUTH BRASIL AND THE SOUTH ATLANTIC. THIS WILL LEAD TO
MOST ACTIVE CONVECTION CONSTRAINING TO MOST OF CHILE AND CENTRAL
ARGENTINA WHILE SEASONALLY QUIET CONDITIONS DOMINATE TROPICAL
SOUTH AMERICA. FIRST TROUGH TO ENHANCE ACTIVITY WILL ARRIVE IN
SOUTHERN CHILE LATE ON TUESDAY. THIS TROUGH WILL ARRIVE
ACCOMPANIED WITH AN ELONGATED FRONT AND A SUBTROPICAL MOISTURE
CONNECTION TO PRODUCE MODERATE RAINS BETWEEN TEMUCO AND LOS LAGOS
WITH AMOUNTS OF 25-50MM/DAY. TROUGH WILL THEN DIG AS IT MOVES
NORTHEASTWARD INTO SOUTHERN CHILE. AS THE TROUGH DIGS AND SURFACE
FRONT MEANDERS NORTHWARD...A MOISTURE POOL WITH PRECIPITABLE WATER
NEARING 35MM WILL BE DRAWN INTO CENTRAL CHILE. THIS WILL SETUP THE
BEGINNING OF THE AFOREMENTIONED HEAVY RAINFALL EVENT. DURING
WEDNESDAY INTO EARLY THURSDAY THE BULK OF THE RAINS WILL
CONCENTRATE BETWEEN PUERTO MONTT AND CHILLAN WITH ACCUMULATIONS OF
35-70MM/DAY. HEAVY RAINS WILL START TO AFFECT THE VALPARAISO
REGION LATE ON WEDNESDAY TO PRODUCE MAXIMA OF 20-35MM/DAY BY EARLY
THURSDAY. EVENT IS TO PEAK DURING THURSDAY INTO EARLY
FRIDAY...WHEN EXPECTING ACCUMULATIONS OF 75-125MM/DAY BETWEEN THE
SOUTHWESTERN COQUIMBO REGION AND CURICO/TALCA. NOTE THAT LARGEST
ACCUMULATIONS ARE EXPECTED IN NORTHWESTERN SLOPES. TO THE SOUTH
BETWEEN CHILLAN AND VALDIVIA EXPECTING MAXIMA OF 20-45MM/DAY.
AMOUNTS WILL DECREASE DURING FRIDAY. BY FRIDAY INTO EARLY SATURDAY
EXPECTING MAXIMA OF 15-30MM/DAY IN THE COQUIMBO REGION...AND
MAXIMA OF 05-10MM/DAY IN INLAND LOCATIONS BETWEEN THE VALPARAISO
AND LOS LAGOS REGION.

AS TROUGH AMPLIFIES AND SLOWLY CROSSES THE ANDES INTO
ARGENTINA...THE ADVECTION OF CYCLONIC VORTICITY WILL AID
CONVECTIVE DEVELOPMENT. MOISTURE WILL BE SLOWLY RETURNING AS THE
PATTERN WILL FAVOR DE DEVELOPMENT OF A LOW-LEVEL JET FROM BOLIVIA
SOUTH INTO NORTHERN PATAGONIA AND THE SOUTHWESTERN ATLANTIC.
INITIALLY...EXPECTING STRONG THUNDERSTORMS TO DEVELOP DURING
TUESDAY ALONG A STATIONARY FRONT LINGERING ACROSS RIO GRANDE DO
SUL-SOUTHERN CORRIENTES. THIS WILL PRODUCE ACCUMULATIONS OF
25-50MM/DAY. CONFIDENCE ON THE EXACT LOCATION OF THE STRONGEST
CONVECTION DECREASES AFTERWARDS AS MODELS DIVERGE ON THE ADVECTION
OF SHORT WAVE ENERGY. YET...EXPECTING HEAVIEST THUNDERSTORMS
LIKELY IN THE SOUTHERN PORTIONS OF THE BUENOS AIRES PROVINCE TO
PRODUCE ISOLATED MAXIMA OF 20-45MM/DAY DURING WEDNESDAY INTO EARLY
FRIDAY. RAINFALL MAXIMA OF 10-15MM/DAY WILL ORGANIZE TO THE WEST
ON THURSDAY STRETCHING FROM MENDOZA SOUTH INTO NEUQUEN. COLD FRONT
WILL ORGANIZE AND START ADVANCING SLOWLY TO THE NORTHWEST ON
FRIDAY. THIS WILL SETUP STRONG LOW-LEVEL MOISTURE CONVERGENCE FROM
CORDOBA SOUTHEAST INTO THE RIO DE LA PLATA.

NORTH OVER THE CONTINENT SEASONALLY QUIET PATTERN WILL DOMINATE
THE DOMAIN WITH ACTIVITY CONSTRAINING TO THE NORTHEASTERN COAST OF
BRASIL IN TRADE WIND CONVERGENCE...AND TO THE NORTHERN AMAZON
NORTH OF 02S.

ROMERO...DMC (CHILE)
FARINA...DMH (PARAGUAY)
GALVEZ...WPC (USA)
$$




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