MON 8/8 AM...IRENE NOW A THREAT TO EAST COAST....

SW46TER · Senior Member Joined: Jul 11, 2005 Posts: 1197

As I stated a few days ago, a weak tropical system is less influenced by upper air steering (ie: trofs that go by to the North) and more influenced by low level steering (Easterly Trade Winds). Irene has not strengthened in the past 2 days despite pulses of convection. In fact, as the NHC stated in their morning discussion, it is possible that Irene has even weakened (temporarily) to a Depression. If you watch the cumulus clould pattern to the West of Irene, you can clearly see a steady due West movement between 50 and 65 West

http://www.ssd.noaa.gov/PS/TROP/DATA/RT...-loop.html

This is the low level flow and a weak Irene should stay Westerly until at least 65 West. The NHC uses the GFS model which almost always early in the game forecasts too far North as it consistently underestimates the strength of the Bermuda High. This will place the East Coast from Jacksonville North at risk this time next week. My gut feeling is this curves North of FL/GA and threatens SC/NC. More later...............

SW46TER · Senior Member Joined: Jul 11, 2005 Posts: 1197

I know it sounds pompous and arrogant, but this storm is not going to turn NW like the NHC still has posted as it's 11am track. This storm as stated before, has remained weak enough to bust trough the trof that went by to the North the past few days, and ala Franklin...has been pesky enough to withstand the tremendous shear it's been subjected to. The storm is clearly marching Westward and as time goes on it will come under the influence of the Bermuda High which will continue to steer her West until at least 70 degrees West longitude. After that,(late this weekend) the ultimate track of the Cat 2 Hurricane (yes...It will intensify under the Ber. High) will be determined by the Westward expansion of the High....which will be determined by the depth of a trof in the Ohio Valley heralding the end of the serious heat this summer in the Northern Plains/ Upper Mid-West. While I will still stick with my SC/NC landfall idea for now (the European operational Model now brings Irene close to Myrtle Beach Smile

) FLORIDA IS NOT OFF THE HOOK YET !!!. As long as the storm is still between 20 and 30 N and is moving West, it is still heading this way. I will update as necessary.............Note: There is an interesting little swirl in the NE Bahamas. It most likely will not affect land, but may develop into a depression later this week.. enjoying favorable conditions.

chris

Jeff, I could definitely see Irene forming into more than what it is now. The loop that you included shows signs of fair definition. Another thing I noticed is that its tracking due west at the moment. Could be interesting for the east coast.

Chris

SW46TER · Senior Member Joined: Jul 11, 2005 Posts: 1197

THIS IS HOW THE NHC EXPLAINED WHAT I WROTE AT 3:30 THIS AFTERNOON.....................................

WTNT44 KNHC 092100
TCDAT4
TROPICAL DEPRESSION IRENE DISCUSSION NUMBER 21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
ISSUED BY THE HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
5 PM EDT TUE AUG 09 2005

VISIBLE SATELLITE IMAGERY THIS AFTERNOON INDICATES THAT IRENE
APPEARS TO BE UNDERGOING A METAMORPHOSIS. THE CLOUD STRUCTURE
ASSOCIATED WITH THE TROPICAL CYCLONE IS GRADUALLY BECOMING MORE
SYMMETRIC...CIRRUS OUTFLOW EMANATING FROM IT IS MORE DIVERGENT
...AND THERE ARE OCCASIONAL SIGNS OF BANDING. COMPARED TO 24 HOURS
EARLIER...IRENE IS CERTAINLY BETTER ORGANIZED. ALL SATELLITE
AGENCIES EXCEPT AFWA ARRIVED AT DVORAK CLASSIFICATIONS BELOW
TROPICAL STORM STRENGTH. ON THIS BASIS...IRENE IS KEPT A TROPICAL
DEPRESSION AT THIS TIME.

THERE WERE SOME DIFFERENCES CONCERNING THE INITIAL POSITION OF THE
DEPRESSION...BUT POSITION ESTIMATES YIELD A SIX HOUR MOTION OF
280/8. IN THE SHORT TERM...IRENE MAY NOT REGAIN ENOUGH
ORGANIZATION TO BE VERTICALLY COUPLED. THUS IT WILL LIKELY ASSUME
A HEADING AND SPEED MORE COMPARABLE WITH THE LOWER LEVEL FLOW.
THEREAFTER...THE FORECAST BECOMES MORE PROBLEMATIC. OVER THE NEXT
FEW DAYS...THE 12Z ECWMF AND NOGAPS MODELS INDICATE THAT IRENE WILL
MOVE UNDERNEATH A MID LEVEL RIDGE LYING OVER THE WESTERN ATLANTIC
...WHICH SHOULD KEEP THE STORM ON A MORE WESTERLY TRACK. ON THE
OTHER HAND...THE 12Z UKMET SHOWS A SHORTWAVE TROF ERODING THE RIDGE
ENOUGH TO CAUSE A TURN TOWARD THE NORTH AROUND 72 HOURS.

THE FUTURE TRACK OF IRENE DEPENDS VERY MUCH ON THE EVOLVING LONGWAVE
PATTERN IN THE MID LATITUDES LATER ON IN THE FORECAST.
SPECIFICALLY...A BLOCKING RIDGE OVER ALASKA AND AN AMPLIFICATION OF
A DOWNSTREAM TROF OVER THE NORTH CENTRAL/NORTHWESTERN U.S. WILL
DETERMINE HOW ROBUST THE WESTERN ATLANTIC RIDGE WILL BE AND HOW
LONG IT STAYS IN PLACE. AT THIS TIME...GIVEN THE GOOD AGREEMENT ON
THE LONGWAVE PATTERN IN THE NCEP AND ECWMF ENSEMBLE MEAN SOLUTIONS
WHICH DEPICT A CLOSED ANTICYCLONE TO FORM OVER THE WESTERN ATLANTIC
AT THAT RANGE...THE TRACK OF IRENE HAS BEEN SHIFTED FARTHER SOUTH
AND WEST.

AFTER SEVERAL DAYS OF ENDURING MODERATE VERTICAL WIND SHEAR IN
ASSOCIATION WITH A SHARP UPPER TROF TO ITS NORTHEAST...MODELS
GENERALLY AGREE THAT IRENE WILL ENTER A MORE FAVORABLE ENVIRONMENT
FOR DEVELOPMENT. THEY FORECAST THE SHEAR VECTOR OVER THE
DEPRESSION TO SHIFT FROM A NORTHWESTERLY TO EAST AND BECOME WEAKER
WITHIN 24 TO 36 HOURS. AFTER THIS TIME...IRENES POSITION SOUTH OF
THE RIDGE OVER THE WESTERN ATLANTIC SHOULD FAVOR A GENERAL
INTENSIFICATION. THE FORECAST INTENSIFICATION IS VERY MUCH IN LINE
WITH THE SHIPS MODEL THROUGH THE PERIOD

SW46TER · Senior Member Joined: Jul 11, 2005 Posts: 1197

Quick update..................ignore the 5AM nonsense the NHC says about Irene currently being just an open wave with no center. The center is redeveloping on the South side of the cloud shield where the convection has tended to fire up over the past 36 hrs. While the Dvorak system may not even deem it a depression early this morning, if the lazy bums would send a plane in there, they would find a circulation. But since they didn't deem the storm a threat to land..............no plane yet. Make no mistake, this storm will begin to strengthen...........probably today. And I have confidence this will blow up quickly into a strong Cat 2 or borderline Cat 3 if it is still in the water next Tuesday approaching the East Coast..........................Later

SW46TER · Senior Member Joined: Jul 11, 2005 Posts: 1197

***EDITED FOR SPACE AND TO THE POINT*****

TROPICAL DEPRESSION IRENE DISCUSSION NUMBER 24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT WED AUG 10 2005

THE CONVECTIVE CLOUD PATTERN THIS MORNING HAS IMPROVED SIGNIFICANTLY COMPARED TO 24 HOURS AGO. IT IS STILL DIFFICULT...HOWEVER...TO DETERMINE AN EXACT CENTER LOCATION...ESPECIALLY IN CONVENTIONAL IMAGERY. A LOW-LEVEL CENTER COULD BE FARTHER SOUTH NEAR 21N...BUT I PREFER TO REMAIN FARTHER NORTH AS GLOBAL MODEL GUIDANCE HAS CONSISTENTLY DISPLAYED A 20-30 DEGREE RIGHT-OF-TRACK BIAS THE PAST 48 HOURS. THIS IS NOT SURPRISING SINCE THE MODELS HAVE KEPT IRENE WEAK OR HAVE EVEN DISSIPATED IT...ALL THE WHILE MID-LEVEL NORTHERLY FLOW HAS BEEN KEEPING THE CYCLONE FARTHER SOUTH ON A MORE WESTWARD TRACK.THE OFFICIAL FORECAST IS TO THE LEFT OF THE PREVIOUS ADVISORY AND IS ON THE EXTREME LEFT...OR SOUTH ...SIDE OF THE NHC MODEL GUIDANCE ENVELOPE. IF A WESTWARD MOTION CONTINUES TODAY AND THE CENTER DOES NOT REFORM FARTHER NORTH...THEN THE TRACK WILL HAVE TO BE SHIFTED EVEN MORE TO THE LEFT ON THE NEXT ADVISORY. UPPER-LEVEL OUTFLOW HAS BECOME BETTER ESTABLISHED OVER THE PAST 12 HOURS AND IT IS EXPECTED TO CONTINUE TO IMPROVE FOR THE NEXT 3 DAYS. IT IS POSSIBLE THAT IRENE COULD REACH HURRICANE STRENGTH BEFORE THE END OF THE FORECAST PERIOD.

STEWART

chris