11pm Frances Report

We have a hurricane watch along with much of the bottom half of the Florida coast.

Offical odds for a hit on Miami remain almost unchanged, with the bulls-eye still just enough north of here to make the misery go elsewhere. Our cumulative chance of a strike has risen to 20%, but that's only because the new tables project further out into Saturday. The peak period remans 11% between 8PM Thursday and 8AM Friday. Meanwhile, however, the National Weather Service's discussion of the track, which has been dominated for two days by puzzlement as to why the various different models diverge so much, has taken on a new note.

I don't know why the National Hurricane Center forecasters still have to WRITE THEIR ANALYSIS IN ALL CAPS just like they probably did in the days of the telegraph, but here is the 11pm discussion of the meteorology? I have taken the liberty of adding bold to the parts that caught my eye:

RECON THIS AFTERNOON AND EVENING INDCIATED THE CENTRAL PRESSURE HAD DECREASED TO 939 MB. A DROPSONDE AT 01/1904Z INDICATED WINDS OF 154 KT…OR 177 MPH…AT THE 850 MB LEVEL. THE HIGHEST 700 MB RECON FLIGHT-LEVEL WIND AT 2210Z WAS 134 KT…EQUAL TO ABOUT A 121-KT SURFACE WIND. BASED ON THIS INFORMATION…FRANCES IS BEING HELD AT 120 KT…WHICH MAY BE A LITTLE CONSERVATIVE.

THE INITIAL MOTION IS 295/12. HOWEVER…THERE HAS BEEN CONSIDERBALE WOBBLE IN THE TRACK THE PAST 12 HOURS DUE TO THE EYEWALL REPLACEMENT CYCLES THAT HAVE BEEN OCCURRING. FRANCES HAS BEEN MOVING WEST-NORTHWESTWARD FOR THE PAST 24 HOURS UNDER THE INFLUENCE OF THE SUBTROPICAL RIDGE TO THE NORTH…WHICH IS EXPECTED TO REMAIN INTACT THROUGH AT LEAST 48 HOURS. THE GULFSTREAM-IV JET AND AN AFRES C-130 HAVE BEEN RELEASING DROPSONDES AROUND THE PERIPHERY OF FRANCES. THE SONDE DATA HAS PRODUCED SOME INTERESTING AND DISTURBING RESULTS. THE HEIGHT DATA FOR THE VARIOUS PRESSURE LEVELS…COMPARED TO 18Z SURROUNDING UPPER-AIR DATA…APPEAR TO BE AT LEAST 20 METERS TOO LOW. HOWEVER…THE WIND DATA CLEARLY INDICATE A MID-TROPOSPHERIC HIGH PRESSURE CENTER NEAR 30N 75W…OR ABOUT 500 NMI NORTHWEST OF FRANCES WITH A RIDGE AXIS EXTENDING WEST-SOUTHWESTWARD ACROSS NORTH FLORIDA AND INTO THE NORTHEAST GULF OF MEXICO. IN THE SHORT TERM… THIS WOULD SUGGEST THAT FRANCES SHOULD CONTINUE MOVING AT 295 OR EVEN 290 DEGREES MOTION FOR THE NEXT 24 HOURS OR SO. ALSO…00Z UPPER-AIR DATA INDICATE THAT THE 18Z NOGAPS AND 12Z UKMET MODELS HAVE VERIFIED THE 00Z 500 MB RIDGE AND HEIGHTS THE BEST…WHILE THE 18Z GFS AND GFDL MODELS WERE MUCH TOO WEAK…AT LEAST 20 METERS TOO LOW…WITH THE STRENGTH OF THE RIDGE. SINCE THE 00Z MODEL RUNS WILL HAVE THE NEW GPS DROPSONDE DATA INCLUDED IN THOSE RUNS FOR THE 06Z ADVISORY…NO SIGNIFICANT CHANGE IS BEING MADE TO THE PREVIOUS FORECAST TRACK. HOWEVER…WITH HIGH PRESSURE LOCATED TO THE NORTHWEST OF FRANCES…I WOULD NOT BE SURPRISED TO THE 00Z MODEL TRACKS SHIFT A LITTLE MORE WESTWARD.

That would be…this way.

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2 Responses to 11pm Frances Report

  1. Eli Rabett says:

    They started with teletypes…..

  2. Michael says:

    Yes, fine, but do they still use them? Does anyone?

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