Ok, this here is from the Thu Sept. 11, 2003 Hurricane Isabel Discussion, however is still a good source of info on ridges and troughs:
THE BIG QUESTION CONTINUES TO BE WHAT WILL HAPPEN BEYOND THE 5-DAY
FORECAST PERIOD. IT IS STILL IMPOSSIBLE TO STATE WITH ANY
CONFIDENCE WHETHER A SPECIFIC AREA ALONG THE U.S. COAST WILL BE
IMPACTED BY ISABEL. THIS WILL LIKELY DEPEND ON THE RELATIVE
STRENGTH AND POSITIONING OF A MID-TROPOSPHERIC RIDGE NEAR THE EAST
COAST AND A MID-LATITUDE TROUGH TO THE WEST OR NORTHWEST AROUND THE
MIDDLE OF NEXT WEEK. UNFORTUNATELY...WE HAVE LITTLE SKILL IN
PREDICTING THE EVOLUTION OF STEERING FEATURES AT THESE LONG RANGES.
Note that it was written just 7 days before Isabel hit North Carolina and they still had no clue where the ridge and trough were going to set up. You can guess now, but will most likely be wrong, we can't predict with confidence where it is going to set up 7 days out, let alone a month...I hope this answers your question...no one knows where or how intense until it actually is about to hit.
Hope this helps
