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NAVY HYDROGRAPHIC CENTRE CHM CATARINA: A CASE STUDY ON THE SYSTEM FORMED IN THE SOUTH ATLANTIC

NAVY HYDROGRAPHIC CENTRE CHM CATARINA: A CASE STUDY ON THE SYSTEM FORMED IN THE SOUTH ATLANTIC. 25 00Z. 25 12Z. 26 00Z. 26 12Z. 27 00Z. 27 12Z. 28 00Z. 28 12Z. 29 00Z. NHC (2618Z run). 27 00Z. 27 12Z. 28 00Z. 28 12Z. 29 00Z. 29 12Z. NHC (2712Z run). 28 00Z. 28 12Z. 29 00Z.

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NAVY HYDROGRAPHIC CENTRE CHM CATARINA: A CASE STUDY ON THE SYSTEM FORMED IN THE SOUTH ATLANTIC

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  1. NAVY HYDROGRAPHIC CENTRE CHM CATARINA: A CASE STUDY ON THE SYSTEM FORMED IN THE SOUTH ATLANTIC

  2. 25 00Z

  3. 25 12Z

  4. 26 00Z

  5. 26 12Z

  6. 27 00Z

  7. 27 12Z

  8. 28 00Z

  9. 28 12Z

  10. 29 00Z

  11. NHC (2618Z run)

  12. 27 00Z 27 12Z 28 00Z

  13. 28 12Z 29 00Z 29 12Z

  14. NHC (2712Z run)

  15. 28 00Z 28 12Z 29 00Z

  16. NHC (2800Z run)

  17. 28 12Z 29 00Z 29 12Z

  18. HRM

  19. USP

  20. Warm waters (min 26.5ºC) in a sufficient depth (at least 50 m), to feed the “heat machine”; layers relatively wet near the mean troposphere (5 km); a minimum distance from the Equator (≈ Lat > 5º). The Coriolis force cannot be neglected, for the occurrence of the gradient wind balance. In the absence of this force, the low pressure of the perturbation cannot be maintained; convergence on surface; and low values of vertical wind shear (below 20 knots between 850 and 200 hPa). High values of this shear may break the cyclone. FAVOURABLE CONDITIONS FOR HURRICANES FORMATION

  21. Around 20ºS of latitude, the vertical movement of the air is subsiding => subtropical high (semi-permanent system). The subsiding air warms and generates a temperature inversion (stable layer), preventing the formation of the hurricanes; strong winds on high levels prevent the development of storms by dispersing latent heat and breaking the energy supply of these storms; mean wind shear between 850 and 200 hPa are greater than 20 knots; and the easterly waves from Africa (convergent winds that burst storms) are virtually unknown in the tropical South Atlantic. UNFAVOURABLE CONDITIONS IN THE SOUTH ATLANTIC

  22. 30% 17% 11% 1% 5% 12% 12% 13% Occurrence

  23. Hurricaneis a low pressure system which takes its energy, primarily, from the evaporation of sea water and from condensation associatedto convective clouds; mean latitude storms (lows associatedwithfrontal systems), take their energy, primarily, from the horizontal temperature gradients; hurricanes havestronger winds near the surface (a consequenceof a warm centre); mean latitude storms havestronger winds near the tropopause (a consequenceof a warm centre in the stratosphereanda cold centre in the troposphere). DIFFERENCES BETWEEN HURRICANES AND MEAN LATITUDE STORMS

  24. HurricanesDevelopment Stages 1- Tropical Disturbance 2- Tropical Depressionwind 22-33 knots - force 6-7 3- Tropical Storm Moderate  wind 34-47 knots - force 8-9 Severe wind 48-63 knots - force 10-11 4-Hurricanewind ≥ 64 knots - force 12

  25. Cross Section

  26. The hurricane structure

  27. The strong winds near the surface, which converge toward the centre,never reach the eye of the hurricane, forming a cylinder of calm winds. The most destructive part of the hurricane is around the eye wall, where the wind blows in the same direction of the movement of the hurricane.

  28. movingabove colder waters; movingover the continent; movingover anarea where large scale flux isn’t favorable to its development. Hurricanes may dissipate by several ways:

  29. TRMM (Tropical Rainfall Measuring Mission) estimated the radius of the eye of 20 to 25 km and the radius of the hurricane ofabout 500 km. It is believed that Catarina was a system with hybrid characteristics, formed as a tropical transition. CATARINA

  30. CATARINA CHM, on 27th March, issued severe weather warnings and characterised the system as follows: PART TWO - WEATHER ANALYSISAT 271200 LOW 1000 Hpa AS AN EXTRATROPICAL CYCLONE AT 29S046W WITH TROPICAL CHARACTERISTICS MOVINGAT 6/8 KNOTS TO W/SW. THE PROGNOSISIS TO REACH THE COAST OF RIO GRANDE DO SUL AND SANTA CATARINA AT 290000. WARNING NR 059/2004 GALE WARNING ISSUEDAT 1400 GMT – SAT – 27/MAR/2004 NEAR GALE/SEVERE GALE WIND FORCE 7/9 SW/SE WITHGUSTS AFFECTINGAREAS BRAVO/CHARLIE SOUTHOF 27S ANDAREA ALFA NORTHOF 32S. VALID UNTIL 281800 GMT.

  31. 150 km/h winds were estimatedover the continent; 40 citieswere affected in the state of SC; 5m waves near the coast; 2 boatswere sunk with life losses; 2 people were killed and 76 were hurt over the continent; and in Criciúma, accumulated rain: 150 mm in about 3 hours. NUMBERS OF THE DESTRUCTION

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