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Atlantic Hurricane Activity 2007

This study analyzes the interannual variability of the warm pool in the Atlantic and its relationship to hurricane activity. It also examines the influence of Pacific ENSO on the warm pool and emphasizes the need for skillful numerical model forecasts.

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Atlantic Hurricane Activity 2007

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  1. AtlanticHurricaneActivity2007

  2. Composites of the WH Warm Pool (1950-2000) 5 Largest WPs 5 Smallest WPs Dark contour ==> SST = 28.5°C • Interannual variability of the AWP is large • Large AWPs are almost three times larger than small ones

  3. Index of the WHWP • The warm pool area follows closely the tropical North Atlantic SST • Interannual variability is large, some related to Pacific ENSO

  4. 2 = 40% 2 = 95% ==> we need skillful numerical model forecasts!!

  5. Of the 18 years with small warm pools 3 busy years, 23 storms Of the 18 years with large warm pools 11 busy years, 82 storms 54 Years of Atlantic Hurricanes (1950-2003) Busy hurricane years = years for which the number of late-season hurricanes fall within the top tercile of all years

  6. ENSO: shear is increased but moist instability (CAPE) also increases Warm pool: moist instability (CAPE) and shear work together

  7. Summary of Summer Responses to AWP

  8. 8 North Atlantic: SST, SST Tendency, OLR, 850mb Wind Slight warming of IAS, normal SST over the TNA & MDR. Dry over Caribbean & ENP regions. Warming in Gulf of Guinea implies a weak West African Monsoon, south-shifted ITCZ. Tendency toward a negative North Atlantic tripole pattern.

  9. Recent Evolution of Equatorial Pacific SST (shaded, ºC), Surface Zonal Wind (contour, m/s) and Upper Ocean (0-300m) Heat Content Anomaly (shaded, ºC) and MJO Activities 9 Since mid-May 2007, two oceanic Kevin wave episodes were evident in heat content (HC) anom., which have brought HC in the central-eastern Pacific from below-normal to near normal from May to June, and from near normal to below-normal from June to July. Corresponding to the recent negative HC surge , SST has transitioned from near normal to below-normal between 140W and 110W in mid-July. The intraseasonal variability in the ocean was apparently associated with the intraseasonal surface wind variability related to the Madden Julian Oscillation, which was represented by 200mb velocity potential anom.

  10. 10 CFS Nino3.4 Forecasts from Different Initial Months Missed the onset of the 2006/07 El Nino. Underestimated the amplitude of the 2006/07 El Nino. Missed the fast termination of the 2006/07 El Nino. Forecast La Nina to be developed during late summer to autumn of 2007.

  11. 2007 season 14 5 2 67 But: Atlantic 2007 least active in 50 years! Weak West African monsoon Normal TNA SST (MDR) Weak and/or late La Niña AMO negative tendency

  12. 2007 season ACE activity index

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