Patterns of Significant Weather Events over South America

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Patterns of Significant Weather Events over South
America

• Richard H. Grumm,
• NCEP Contributions from
• Yuejian Zhu, Zoltan Toth, and Michel Davison

2
What we shall attempt to cover

• Examples of significant weather events
• A wide range of event types
• Focus on the larger scale patterns using
  re-analysis data
• Why?
• To recognize the patterns
• Improve situational awareness
• Identify these patterns in NWP and EPS output

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Patterns of Significant Events

• Many event types have distinct patterns and
  features
• Synoptic and frontal rainfall event types
• West Coast heavy precipitation types
• Severe weather event types
• Heat and cold episode event types
• Models and ensembles can typically
• Predict the large scale patterns
• Replicate the conditions from previous and
  similar events

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Examples of Patterns

• Rare snow fall in Buenos Aires- 10 July 2007
• Associated with a long cold episode
• MODIS imagery of the snow in Argentina
• Large anticyclone, cold air, dry air, and 500 hPa
  wave produced the light snow.

First time since 1918, snow fell in Buenos
Aires, Argentina, late on July 9, 2007. AP report
from MODIS website.
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Patterns July 2007 cold episodevery dry air,
anomalous anticyclone, and strong trough
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Heat Episode-Jan-Dec 2000Fires January 2001

• ARGENTINA (fire) EFE via COMTEX reported that
  rural fires that have been triggered by the
  southern hemispheres scorching summer heat began
  in mid-December this year. The fires have
  reportedly destroyed crops and cattle-grazing
  land in four provinces, including the following
  1.5 million hectares in La Pampa province,
  400,000 hectares in Mendoza, 100,000 hectares in
  San-Luis in central Argentina and 50,000 hectares
  in Formosa, near the border with Paraguay. Seven
  individuals reportedly died on Friday (5th) as
  they battled fires on a farm in southern Mendoza
  province with rudimentary techniques. Another
  individual reportedly died on Friday after being
  severely burned and hospitalized in the town of
  Humada in La Pampa.

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Heat Event with FiresJanuary 2001-subtropical
ridge
Key Points First warm episode was in Dec January
had large 500 hPa ridge, above normal 850 hPa
temperatures and dry air. Features models and EPS
predict well!
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Convective Severe Weather Events

• Favorable conditions often present over
  southeastern South America
• Area favorable for thunderstorm winds, heavy
  rainfall, and large hail.
• One of the preferred regions of the world for
  severe weather? September through May
• Experience organized events and weakly forecast
  events? severe weather map

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Severe Thunderstorm Parameter and potential
Brooks et al. National Severe Storm Laboratory
USA
Based on re-analysis data. (Brooks et al
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Brooks et al. National Severe Storm Laboratory
USA
Based on re-analysis data. (Brooks et al)
Tornadic environments are by far the most common
in the central United States, with lesser areas
in southern Brazil and northern Argentina.
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Severe Weather Overviewhttp//ams.confex.com/ams/
pdfpapers/102247.pdf

• Peak season Sept-May
• Key ingredients
• Low-level moisture
• Convective instability (K,TTI,SSI, and CAPE)
• Vertical wind shear ? modulates storm types based
  on linear or curved profile of the hodograph.
• Key references Ernani de Lima Nascimento and
  Charles A. Doswell III

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Argentina Hail Stormhttp//www.ncdc.noaa.gov/oa
/climate/extremes/2001/january/rapidres0101.html

• ARGENTINA reported that at least 5 individuals
  were killed during a four and a half hour storm
  that included heavy rains and hail. The storm
  reportedly pounded Buenos Aires and the
  surrounding area on Wednesday (24th) , and the
  Argentine weather bureau reported that 145.2mm
  (5.7 inches) of rain fell on Buenos Aires during
  the storm. Road traffic, plane, railway and
  subway services were all reportedly disrupted,
  and approximately 270,000 homes suffered from
  power outages.

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Large Subtropical RidgeWeak forcing event
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11 November 2003Thunderstorm Winds? Strong
forcing low-level jet and frontal boundary? Shear
and instability
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Brazil Indaiatuba tornado event24 May 2005

• F3 Tornado was captured on video
• Area affected
• Strong low-level jet with strong northwest flow
  at 850 hPa.
• High PW air in warm sector indicating a frontal
  system in the affected region? proxy for CAPE
• Surface trough and cyclone in general region?
  source of low-level vorticity and shear.

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24 May 2005Shear and moisture? strong low-level
jet and high PW in region.
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Thunderstorm Wind Damage in Sao Paulo State Brazil
Thunderstorm winds downed power lines in evening
of 22 July 2002 Winds from isolated severe
storms. Damage to property to include power
lines is a good indicator of severe
weather. Lima and Menezes (2004)
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26 January 2007 western Argentina Hail
Not sure exactly where? Dry line type event?
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Line of Thunderstorms 16 February 2007
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Supercell hail event 6 July 2003

• Large hail from long-lived thunderstorms
• HP type supercell with hail and heavy rains
  producing flooding
• Storm created wind damage and downed power lines
  leaving over 60K people without power.

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Lapse Rates
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Large scale conditions
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Severe Weather Summary

• South American Tornadoes are common and appear to
  occur with strong shear and instability
• Severe weather is common to include organized
  convection in the Sep-May time frame
• Lines (F0-F1) and supercells(F1-F3) damage
• Hail
• Pulse storms
• http//www.stormtrack.org/forum/showthread.php?t1
  0771

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Heavy Rainfall Events

• Primary large scale event types
• Tropical systems ? those interacting with fronts
  can be exceedingly large rainfall producers
• Synoptic systems associated with south-north
  fronts
• Frontal systems associated with quasi east-west
  fronts
• West Coast orographic Events ? terrain component
• Mesoscale Events
• MCS/MCC
• Localized convective heavy rainfall events.

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Chile Floods 13 July 2006

• Heavy rainfall caused the floods
• MODIS picked up the sediment deposited by the
  swollen rivers
• Nearly 100K people affected
• Area was declared a disaster area
• Patterns of West Coast Rainfall
• Surge of high PW air into mountains
• Strong low-level winds into mountains
• Jet entrance region over affected locals.

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Strong Jet and moisture into terrain11-12 July
2006
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30 March-01 April 2007

• Heavy rains across Argentina and southern Uruguay
• Quasi east-west frontal system high PW and u-wind
  anomalies
• CMORPH picked up the rainfall amounts
• MODIS satellite saw flooded rivers from late
  March as skies cleared in early April

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30-31 March East-West zone of high moisture
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8-10 September 2003
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CMORPH Rainfall
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23-29 November 2003

• Flooding and heavy rainfall in Paraguay and
  southern Brazil
• Good CMORPH rainfall data for this event
• Surge high PW air and northerly v-winds into the
  affected region.

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Large scale pattern
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CMORPH Rainfall
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14-18 August

• South-central Chile rainfall
• CMOPRH did not catch more orographic event
• West Coast type

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CMORPH data
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Some Notable Cases

• 5-6 May 2008
• 26-27 March 2004
• Bolivian Floods Jan-Feb 2008
• 26-27 March 2008 rain began with

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The Brazilian hurricane on March 26, 2004, as
seen by the Moderate Resolution Imaging
Spectroradiometer (MODIS) on the Terra satellite
Hurricane Catarina The storm killed at least
three people and caused an estimated 350 million
(2004 US dollars) in damages.
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23-27 Jan 2008 heavy rain Bolivian and Paraguay
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cold and moist over the region? instability
rainfall?
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26 Jan 2008No good wind signal over Bolivia
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4-6 May 2008http//oglobo.globo.com/pais/mat/2008
/05/06/ciclone_atingiu_200_mil_gauchos_desalojou_3
_mil-427247286.asp
Flooding in Santa Catarina
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4 May 2008
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4 May 2008
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5 May 2008
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5 May 2008
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Predicted event 27-29 Aug 2008
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Heavy Rainfall Events? Summary

• Looked at event types and associated pattern
• Synoptic systems associated with south-north
  fronts
• Frontal systems associated with quasi east-west
  fronts
• West Coast orographic Events ? terrain component
• Mesoscale Events
• Large scale patterns should be predictable in ou
  EPS and high resolution deterministic model.
• Leverage this and precipitation probabilities for
  maximized patterns and potential for a
  significant rainfall event.

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Notes

• Cold outbreaks To get a continental polar, or
  Antarctic Continental, air mass you need a high
  amplitude sinusoidal pattern with cold air
  tracking north across the Antarctic
  Peninsula-Drake Passage to Patagonia in
  Argentina.  For this to happen, the mid level
  ridge axis must be around 80W.  As the air enters
  the srn cone, the Andes then "shelter" the cold
  air as it pushes north, retaining the continental
  characteristics.  If the ridge extends along
  65w/70w, the air mass tracks over water and it
  quickly modifies.
• McTaggart-Cowan, R., Bosart, L. F., Davis, C. A.,
  Atallah, E. H., Gyakum, J. R., and Emanuel, K. A.
  (November 2006). "Analysis of Hurricane Catarina
  (2004)". Monthly Weather Review 134 (11)
  302953. doi10.1175/MWR3330.1.

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Other events

• July 26, 2006, around 18Z they had a severe
  weather event affecting lower Mesopotamia
  Valley-Buenos Aires Province-Uruguay, with large
  hail causing a lot of property damage over
  Buenos Aires City.Aug 11, 2008, between 19-20Z,
  supper cell over Uruguay, with an F2 tornado
  moving through north-central portions.Aug
  15-18, 2008, heavy rainfall event across
  srn/central Chile.