eastcoastFL wrote:dolebot_Broward_NW,
when we are talking about things being DAYS away how can we be so sure that these steering currents wont change or that the trough will weaken? I highly doubt the trough change you can now see it plain as day coming straight at irene but the steering currents could change, couldnt they? I mean this storm is still 48 hrs from the nw bahamas /
Well like I said - unexpected things happen. I'm no met, but certain things they can see well in advance. Meteorology is very complicated. A lot of it depends on timing, and sometimes things are overlooked, details missed, etc. WIth that Jeanne here is some insight as to what happened from the NHC Jeanne report:
While Jeanne was dumping rain over the Caribbean countries, Hurricane Ivan moved over the Gulf of Mexico and inland across the southeastern United States. By 18 September, Ivan's mid-level circulation had combined with an extratropical short wave trough in the westerlies and moved to the northeastern U.S. coast where it eroded the ridge to the north of Jeanne. This placed Jeanne in a weak steering flow that persisted for five days. Jeanne first moved slowly northward over the southeastern Bahamas as a tropical storm and then moved in an anticyclonic loop about 500 n mi east of the northwestern Bahamas. Jeanne gradually strengthened to a hurricane with 85-kt winds by the time it completed this loop on 23 September.
By 23 September, the extratatropical trough previously located over the northeastern U.S. coast moved eastward and was replaced by a large deep-layer migratory ridge that propelled Jeanne on a track just north of due westward. On 24 September, Jeanne moved over its own previous track from a few days earlier and encountered cooler waters caused by upwelling from the hurricane. This is believed to be a factor in the decreasing of the maximum winds from 85 kt to 70 kt by 0000 UTC on 24 September. Continuing westward at 10 to 12 kt and moving away from the upwelled cooler water, the winds increased to 100 kt (category three on the Saffir/Simpson hurricane scale) by 1200 UTC on 25 September as the center moved over Abaco Island and then Grand Bahama Island in the northern Bahamas. Jeanne made landfall on the east coast of Florida early on 26 September with the center of its 50-n mi diameter eye crossing the coast at the southern end of Hutchinson Island just east of Stuart at 0400 UTC on 26 September.
The largest 120-h official track forecast errors were for forecasts made on 16 and 17 September, when Jeanne was moving across Hispaniola. These forecasts failed to capture the turn to the north and subsequent loop that occurred from 18 through 23 September, but instead showed a track directly toward the southeastern United States.
The difference here is that there isn't anything unexpected going on.
