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 501 
 WTPZ44 KNHC 060240
 TCDEP4
 
 HURRICANE NORBERT DISCUSSION NUMBER  15
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP142014
 800 PM PDT FRI SEP 05 2014
 
 The satellite presentation of Norbert has improved dramatically
 since the last advisory. A ragged eye is apparent in infrared
 imagery surrounded by a ring of cloud tops colder than -70C. Dvorak
 estimates from TAFB and SAB at 00Z were T5.5/102 kt, and the initial
 intensity is set a bit below that value at 95 kt for this advisory
 given the very rapid change in the satellite appearance and the
 earlier recon data. This recent intensification occurred as Norbert
 moved over waters warmer than 29C, and some additional strengthening
 is still possible in the next few hours. However, SSTs steadily
 decrease along the track going forward, which should result in
 gradual weakening beginning by 12 hours. Steadier weakening is
 expected beyond 24 hours as SSTs fall below 26C and the cyclone
 moves into a drier and more stable airmass. By 72 hours Norbert is
 expected to become post-tropical and then weaken to a remnant low
 around day 4. The new NHC intensity forecast has been adjusted
 upward by 10-15 kt through 24 hours to account for the current
 intensity trend, and is about 5 kt higher than the previous advisory
 after that time. This forecast is a little above the intensity
 consensus through 36 hours and close to the consensus afterward.
 
 Smoothing through some short-term wobbles, the initial motion
 estimate is 320/08. The track forecast reasoning remains unchanged,
 as Norbert will be steered around the western periphery of a mid-
 level ridge centered over the southern United States through 48
 hours. After that time, the ridge weakens as a mid-latitude trough
 moves into the U.S. West Coast. This should result in a weakening of
 the steering currents, leaving the low-level center of Norbert to
 drift slowly northward or move erratically at the end of the
 forecast period. The new NHC track forecast is similar to the
 previous one, but has been adjusted a little to the east to account
 for the initial position and motion. This track is close to the
 TVCE multi-model consensus through 72 hours, and shows little net
 motion after that time.
 
 Moisture from the remnants of Dolly and the Pacific ITCZ is being
 advected northward by the outer circulation of Norbert across
 northern Mexico and into the southwestern United States. This could
 result in heavy rains and life-threatening flash flooding in these
 areas during the next few days. Please see information from your
 local weather office for more details.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  06/0300Z 24.2N 112.8W   95 KT 110 MPH
  12H  06/1200Z 24.9N 113.8W   90 KT 105 MPH
  24H  07/0000Z 25.6N 114.9W   80 KT  90 MPH
  36H  07/1200Z 26.5N 116.1W   65 KT  75 MPH
  48H  08/0000Z 27.3N 117.0W   50 KT  60 MPH
  72H  09/0000Z 29.0N 117.5W   35 KT  40 MPH...POST-TROPICAL
  96H  10/0000Z 29.5N 117.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 120H  11/0000Z 29.5N 117.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
 $$
 Forecaster Brennan
 
 
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