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AtlanticHurricaneActivity2007
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Composites of the WH Warm Pool (1950-2000)
Interannual variability of the AWP is large Large AWPs are almost three times larger than small ones
5 Largest WPs 5 Smallest WPs
Dark contour ==> SST = 28.5°C
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The warm pool area follows closely the tropical North Atlantic SST Interannual variability is large, some related to Pacific ENSO
Index of the WHWP
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2 = 40% 2 = 95%
==> we need skillful numerical model
forecasts!!
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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
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
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ENSO: shear is increased but moist instability (CAPE)
also increases
Warm pool: moist instability (CAPE) and shear work
together
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Summary of Summer Responses to AWP
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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.
North Atlantic: SST, SST Tendency, OLR, 850mb Wind8
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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
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.
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CFS Nino3.4 Forecasts from Different Initial Months
Underestimated the amplitude of the 2006/07 El Nino.
Missed the fast termination of the 2006/07 El Nino.
Missed the onset of the 2006/07 El Nino.
Forecast La Nina to be developed during late summer to autumn of 2007.
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But: Atlantic 2007 least active in 50 years!1) Weak West African monsoon2) Normal TNA SST (MDR)3) Weak and/or late La Niña4) AMO negative tendency
2007season
1452
67
2007 season ACE activity index