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 883 
 WTPZ44 KNHC 040248
 TCDEP4
 
 HURRICANE ISELLE DISCUSSION NUMBER  14
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092014
 800 PM PDT SUN AUG 03 2014
 
 Iselle's satellite appearance has essentially been steady state
 since the last advisory.  The cyclone continues to exhibit many of
 the characteristics of an annular hurricane, with a nearly
 axisymmetric convective structure and a curious lack of convective
 features outside the well-defined cental dense overcast. A circular
 but cloud-filled 20-25 n mi wide eye is also evident in last-light
 visible imagery.  The initial intensity is reduced only slightly to
 95 kt in accordance with the latest CI numbers from TAFB and SAB.
 
 The initial motion estimate is a steady 280/10, with perhaps more of
 a due-west wobble during the last couple of hours.  A mid-latitude
 trough extending southwestward along 130w is forecast to weaken the
 subtropical ridge north of Iselle during the next 24 hours.  The
 effect of the weakened ridge should be a decrease in the cyclone's
 forward motion for a brief period during the next day or two as it
 approaches 140w.  By day 3, the cyclone should find itself south of
 a newly established central Pacific ridge, which should steer Iselle
 west-northwestward at a considerably faster forward speed by days
 4-5.  The track forecast is little changed from the previous one
 and is in the middle of the guidance envelope, very close to the
 multi-model consensus TVCE.
 
 Even though Iselle is moving over marginally warm sea surface
 temperatures, its current annular structure in a very light-shear
 environment suggests that the cyclone might retain a higher
 intensity than the guidance might suggest if the large-scale
 environmental conditions do not vary much at least during the next
 day or possibly two. After that, significantly less favorable
 thermodynamic factors, such as increasingly drier and more stable
 air and water temperatures just below 26C, should result in
 weakening while Iselle nears the Hawaiian Islands.  An accelerated
 weakening may take place as Iselle makes its closest approach to the
 Hawaiian chain when environmental conditions become even more
 hostile.  The intensity forecast is about the same as the previous
 one and is near the multi-model consensus IVCN and the SHIPS/LGEM
 output.
 
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  04/0300Z 15.9N 134.8W   95 KT 110 MPH
  12H  04/1200Z 16.0N 136.2W   90 KT 105 MPH
  24H  05/0000Z 16.0N 137.8W   85 KT 100 MPH
  36H  05/1200Z 16.0N 139.3W   80 KT  90 MPH
  48H  06/0000Z 16.5N 141.3W   75 KT  85 MPH
  72H  07/0000Z 18.1N 146.8W   60 KT  70 MPH
  96H  08/0000Z 20.1N 153.1W   45 KT  50 MPH
 120H  09/0000Z 22.3N 159.2W   40 KT  45 MPH
 
 $$
 Forecaster Kimberlain
 
 
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