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Hurricane Frances Thursday - August 26, 2004 - 9:30 PM
Frances strengthens to a hurricane over the open tropical Atlantic….
Just another example of how difficult intensity forecasting is. Despite all the dry air directly in front of Frances she easily overcame that and strengthened rapidly to a hurricane today. She was definitely showing signs of development at this time last night but I just expected it would be a slower evolution to hurricane status. We are where we are and we need to progress from here.
Latest IR satellite pics show a tropical cyclone that continues to become better and better organized. Outflow is well established in all quadrants and the overall structure continues to become more symmetrical with good banding features.
INTENSITY: Shear is low and Frances will be moving over increasingly warm water. Latest 00Z SHIPS is near 110 mph at this time tomorrow….can't really argue with that…although that could be a little over zealous. From 24-60 hours the intensity should level off as shear increases slightly. Would expect Frances to hover in the 95 - 110 mph range over the next 72-96 hours. Beyond 96 hours as Frances moves north of the Islands over some very warm water (as yet un-churned by a tropical system this season) with continued low shear and an improving ventilation scenario she could attain CAT 3 status as she nears the eastern or southeastern Bahama Islands. Keep in mind intensity forecasting at these time frames has little skill….but given the synoptic setup Frances could become a powerful hurricane if everything falls into place.
Track: Really no significant changes to prior thinking. Latest motion is 295-300 at about 16 mph. Expect this general motion to continue for the next 12-24 hours with perhaps a bend more NW for a time over the weekend as the ridge to the north weakens slightly. Once trof lifts out to the north of the ridge later in the weekend the ridge should re-build back westward to the north of Frances. If this thinking is correct… and it is currently supported by all avail. global models to one degree or another…Frances should turn back more w.n.w. or west.
Guidance varies from the med/deep BAMMs and GFS on the south side of the track window to the UKMET/GFDL/NOGAPS on the north. Latest TPC track is in between and is close to the 12Z EURO. My forecast is to the right of the BAMM guidance and left of the latest TPC track.
My forecast track would take the center of Frances north of the islands by about 100-125 miles.
Longer Range: Again, not much change in my thinking from last night in the longer range time periods. Still feel comfortable with a position near 24N - 72.5W late Thursday or early Friday. Once Frances gets "trapped" under the re-building ridge to her north she should move on a general w.n.w. or west track toward the eastern or southeastern Bahama Islands. From that position she is poised to be a threat…and perhaps a significant threat to the s.e. coast.
Key to forecast at longer ranges as to who has the highest threat will depend to a large degree on how strong and how far west the ridge builds. Some guidance suggests a weakness may develop in the ridge near or off the east coast at longer ranges….that would tend to spare Florida and increase the threat further north….this could also provide a near miss for the east coast if everthing broke just right….on the other hand some guidance holds the ridge in place strongly north of Frances and that would greatly increase the threat to south Florida. Also of importance is how much latitude Frances can gain in the early time ranges.
Bottom line….Frances is likely to become at the very least a threat to the s.e. coast from Florida to the Carolinas as we move into and through labor day weekend.
If you live anywhere from the Fl Keys to Cape Hatteras you'll want to keep close tabs on future updates.
More tomorrow……