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Hurricane Ivan update - 09.13.04


Hurricane Ivan is now expected to meet a fast moving trough that will alter the track. This was the trough predicted in the last hotspots item.

The current tracking parameters for Ivan show a probable landfall somewhere between Mississippi and Alabama. However, the most recent bulletin sees the possibility of a strong fast moving trough to come across the country and tweak the track of Ivan towards the east. This bulletin can be found on hurricane tracking . It reads in part:5 PM EDT MON SEP 13 2004

THE INITIAL MOTION IS 330/08. THE LAST FEW RECON FIXES INDICATE THAT IVAN HAS MADE A SLIGHT TURN TO RIGHT...OR TO THE NORTH-NORTHWEST. THIS MOTION HAS LIKELY BEEN INDUCED BY A COMBINATION OF IMPINGING UPPER-LEVEL NORTHWESTERLY FLOW AND THE MID-LEVEL TROUGH OVER THE NORTH-CENTRAL AND NORTHEASTERN GULF OF MEXICO CAUSING THE RIDGE TO THE NORTH OF IVAN TO WEAKEN. HOWEVER...THE TROUGH IS FORECAST TO SLOWLY LIFT OUT NORTHEASTWARD...ALLOWING THE RIDGE TO BUILD BACK WESTWARD IN ABOUT 12HR. THIS IS EXPECTED TO NUDGE IVAN BACK TO A MORE NORTHWESTWARD MOTION.
This is the current track.Then comes the following new information.

AFTERWARDS...A SECOND TROUGH OVER THE U.S. WEST COAST IS FORECAST TO MOVE QUICKLY EASTWARD AND ERODE THE RIDGE AGAIN OVER THE CENTRAL GULF. THE EROSION OF THE RIDGE... COMBINED WITH INCREASING WEST TO SOUTHWESTERLY MID- TO UPPER-LEVEL FLOW OVER THE NORTHWESTERN GULF OF MEXICO BY 48 HOURS SHOULD TURN IVAN NORTHWARD AND THEN NORTHEASTWARD AS THE HURRICANE APPROACHES THE NORTHERN GULF COAST.

If you check the image in the last article in Hotspots you can see the trough that is now coming up on the radar screens for forecasters. Doc Weather expects that this trough will be forming near to the15th over the Mississippi Valley.