Major Hurricane Igor

[Paranoid]

Forecast to become a hurricane in the next 4-5 days (all models support this), although i am a bit skeptical given that at the very least the NHC forecast something similar for Gaston.

000

WTNT31 KNHC 081459

TCPAT1

BULLETIN

TROPICAL STORM IGOR ADVISORY NUMBER 1

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010

1100 AM AST WED SEP 08 2010

...IGOR FORMS IN THE FAR EASTERN TROPICAL ATLANTIC OCEAN...TROPICAL

STORM WATCH ISSUED FOR SOUTHERN CAPE VERDE ISLANDS...

SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION

-----------------------------------------------

LOCATION...13.7N 23.5W

ABOUT 95 MI...155 KM SE OF THE SOUTHERNMOST CAPE VERDE ISLANDS

MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/HR

PRESENT MOVEMENT...W OR 265 DEGREES AT 8 MPH...13 KM/HR

MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES

WATCHES AND WARNINGS

--------------------

CHANGES WITH THIS ADVISORY...

THE GOVERNMENT OF THE CAPE VERDE ISLANDS HAS ISSUED A TROPICAL STORM

WATCH FOR THE SOUTHERN CAPE VERDE ISLANDS...INCLUDING MAIO...SAO

TIAGO...FOGO..AND BRAVA.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...

* THE SOUTHERN CAPE VERDE ISLANDS...INCLUDING MAIO...SAO TIAGO...

FOGO...AND BRAVA

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE

POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE WITHIN THE NEXT 12 TO

24 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR

PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.

DISCUSSION AND 48-HOUR OUTLOOK

------------------------------

AT 1100 AM AST...1500 UTC...THE CENTER OF TROPICAL STORM IGOR WAS

LOCATED NEAR LATITUDE 13.7 NORTH...LONGITUDE 23.5 WEST. IGOR IS

MOVING TOWARD THE WEST NEAR 8 MPH...13 KM/HR...AND THIS MOTION IS

EXPECTED TO CONTINUE FOR THE NEXT COUPLE OF DAYS WITH SOME INCREASE

IN FORWARD SPEED. ON THE FORECAST TRACK...THE CENTER OF IGOR

SHOULD PASS SOUTH OF THE CAPE VERDE ISLANDS BY TOMORROW.

DATA FROM A MICROWAVE SATELLITE INDICATE THAT MAXIMUM SUSTAINED

WINDS ARE NEAR 40 MPH...65 KM/HR...WITH HIGHER GUSTS. SLOW

STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 50 MILES...85 KM

FROM THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB...29.68 INCHES.

HAZARDS AFFECTING LAND

----------------------

WINDS... TROPICAL STORM CONDITIONS ARE POSSIBLE IN THE SOUTHERN CAPE

VERDE ISLANDS LATER TODAY AND OVERNIGHT.

RAINFALL...IGOR COULD PRODUCE RAINFALL ACCUMULATIONS OF 1 TO 3

INCHES OVER PORTIONS OF THE CAPE VERDE ISLANDS.

NEXT ADVISORY

-------------

NEXT INTERMEDIATE ADVISORY...200 PM AST.

NEXT COMPLETE ADVISORY...500 PM AST.

$$

FORECASTER BLAKE/PASCH

[summer blizzard]

Almost definitely a FISH, however there is a chance that it could eventually hit the eastern USA.

[Jack Wales]

To my untrained eye, the system to its north east looks to be better organised with banding features more evident.

[Mondy]

GFDL has it a Cat 3 by next week

http://moe.met.fsu.edu/cgi-bin/gfdltc2.cgi?time=2010090812-igor11l&field=Sea+Level+Pressure&hour=Animation

[Katherine]

Any reason why 2010 has spawned so many Fish Storms?

[Paranoid]

I think there's favourable upper level winds and above average sea temperatures in the area compared to other years, it was mentioned in Joe B's forecast for the season (i'll see if i can find it). That said, there does seem to be an unusual proportion of Fish systems compared to ones that form in the Caribbean and the GOM.

Edit: Found this from the NHC, should answer a fair few of your questions Katherine =).

http://www.noaanews.noaa.gov/stories2010/20100527_hurricaneoutlook.html

[Iceberg]

Re Fishes and 2010, IMO it's simply because the conditions are so good around cape verde, storms that form east of say 40 degrees have a much longer window to try and find an atlantic ridge weakness, igor is a classic example of this as it has around 8 days to find a ridge weakness, if it does not find one (and ECM and GFS have him turning north just before a US hit), then it will be a miracle.

As to why conditions are so good in the east atlantic, I wouldn't like to guess to be honest other than lots of moisture off Africa and low shear.

Back to Igor and shear will be some kind of issue for the next 48 hrs, beyond this and shear is expected to be less than 10kts which is why the models are all taking him to a hurricane by T120.

Atm the centre isn't really defined IMO as the envelope is so large.

Anyway plenty of time to watch this one and I agree a Fish is most likely, however there is still maybe a 30% chance of a US east coast hit.

[Cookie]

Number 9

[summer blizzard]

Any reason why 2010 has spawned so many Fish Storms?

Essentially its a combination of La Nina and the QBO. Basically, the QBO until August was easterly which meant that heat was pouring off Africa into the Atlantic and then spread west resulting in a large swathe of above average sea surface temperature anomolies. During La Nina, the Indian Ocean tends to be warmer than average resulting in a more active monsoon season over Africa and therefore more tropical waves exiting Africa. This combined with a low shear environment currently is resulting in storms developing in the eastern Atlantic and then recurving. The reason for less storms in the Carribean is because the storms are developing in the eastern Atlantic, the majority of storms that develop in the Carribean are Tropical Waves which have made it across the Atlantic undeveloped.

[Cookie]

[AderynCoch]

Nothing interesting expected for Igor in the next day or so: thereafter conditions become favourable for quicker development. He does indeed look like a fish at this point, but of course it's still far too early to tell for sure. I doubt the Caribbean will need to worry about Igor though.

[Katherine]

Igor's just been downgraded to Tropical Depression.

[Guest]

Anyway plenty of time to watch this one and I agree a Fish is most likely, however there is still maybe a 30% chance of a US east coast hit.

As always, thanks for the detailed post, for those of us less in the know can you explain the whole "Fish" thing please? Thanks! :unsure:

[Cookie]

As always, thanks for the detailed post, for those of us less in the know can you explain the whole "Fish" thing please? Thanks!

Fish I storm that doesn't affect land and stays out to see

[Cookie]

[Iceberg]

Igor has been getting better recently, outflow is starting to be evident etc around a CDO.

The big problem is that Igor and the CDO are very very sheared. the LLCC is in the far east of the convection and is bare of convection across it's entire east side.

Shear should really start easing later today though from the 30kts of current shear down to 20 my later tonight and 15kts or so tomorrow. Intensity won't really increase until convection centres more.

The path of Igor is very much west, slightly north of west at times over the next 5 days, longer time and ALL of the GM's are currently showing a ridge to move off the west coast of the US pushing Igor northwards, In my mind there is little doubt that this will happen and Igor will likely remain a Fish very much like Danielle.

So expect the ridge to be thrown up over the England again....:unsure:

[Iceberg]

Igor is back to Tropical storm strength.

IGOR REMAINS A SHEARED TROPICAL CYCLONE. DURING THE PAST FEW

HOURS...HOWEVER...THE SHEAR HAS BEGUN TO SHOW SIGNS OF ABATING AND

THE LOW-LEVEL CENTER IS NOW FARTHER INTO THE EASTERN PORTION OF THE

CENTRAL DEEP CONVECTION. THE UPGRADE TO STORM STATUS IS BASED ON A

SATELLITE INTENSITY ESTIMATE OF 35 KT FROM TAFB AND A 47-KT

UW-CIMSS 3-HR AVERAGE ADT.

THE INITIAL MOTION IS 280/14. THE INITIAL POSITION AND MOTION ARE

STILL SOMEWHAT UNCERTAIN DUE TO MULTIPLE CIRCULATIONS ROTATING

AROUND THE CENTER OF A LARGER CYCLONIC GYRE. HOWEVER...THE MOTION

IS EXPECTED TO BE BASICALLY WESTWARD FOR THE NEXT 96 HOURS OR SO

ALONG THE SOUTHERN PERIPHERY OF A STRONG SUBTROPICAL RIDGE LOCATED

TO THE NORTH OF THE CYCLONE. BY DAY 5...A SERIES OF WEAK SHORTWAVE

TROUGHS MOVING THROUGH THE BASE OF A BROAD LONGWAVE TROUGH FORECAST

TO BE OFF THE U.S. EAST COAST IS FORECAST BY ALL OF THE GLOBAL

MODELS TO CREATE A WEAKNESS IN THE RIDGE BETWEEN 50W-60W LONGITUDE.

THIS IS EXPECTED TO WEAKEN THE STEERING FLOW AND CAUSE IGOR TO SLOW

DOWN AND ALSO TURN WEST-NORTHWESTWARD. THE OFFICIAL FORECAST TRACK

IS SIMILAR TO THE PREVIOUS ADVISORY AND THE TVCN MODEL CONSENSUS.

[Paranoid]

Igor has strengthened slightly to 45mph, although the satellite images would probably suggest a stronger storm (lots of convection and good outflow) The NHC themselves say that 45mph is conservative and it may be much higher (estimates 50kt) due to uncertainty regarding the location of Igor's centre.

000

WTNT31 KNHC 102044

TCPAT1

BULLETIN

TROPICAL STORM IGOR ADVISORY NUMBER 10

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010

500 PM AST FRI SEP 10 2010

...IGOR GRADUALLY STRENGTHENING OVER THE FAR EASTERN

ATLANTIC OCEAN...

SUMMARY OF 500 PM AST...2100 UTC...INFORMATION

----------------------------------------------

LOCATION...16.7N 33.3W

ABOUT 620 MI...995 KM W OF THE CAPE VERDE ISLANDS

MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/HR

PRESENT MOVEMENT...W OR 280 DEGREES AT 21 MPH...33 KM/HR

MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES

WATCHES AND WARNINGS

--------------------

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

DISCUSSION AND 48-HOUR OUTLOOK

------------------------------

AT 500 PM AST...2100 UTC...THE CENTER OF TROPICAL STORM IGOR WAS

LOCATED NEAR LATITUDE 16.7 NORTH...LONGITUDE 33.3 WEST. IGOR IS

MOVING TOWARD THE WEST NEAR 21 MPH...33 KM/HR. THIS GENERAL

MOTION...ACCOMPANIED BY A GRADUAL DECREASE IN FORWARD SPEED...IS

EXPECTED FOR THE NEXT TWO DAYS.

MAXIMUM SUSTAINED WINDS ARE NEAR 45 MPH...75 KM/HR...WITH HIGHER

GUSTS. ADDITIONAL STRENGTHENING IS FORECAST DURING THE NEXT 48

HOURS...AND IGOR IS EXPECTED TO BECOME A HURRICANE BY SUNDAY.

TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 45 MILES...75 KM...

MAINLY WEST OF THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB...29.59 INCHES.

HAZARDS AFFECTING LAND

----------------------

NONE.

NEXT ADVISORY

-------------

NEXT COMPLETE ADVISORY...1100 PM AST.

$$

FORECASTER STEWART

[Katherine]

Igor has strengthened slightly to 45mph, although the satellite images would probably suggest a stronger storm (lots of convection and good outflow) The NHC themselves say that 45mph is conservative and it may be much higher (estimates 50kt) due to uncertainty regarding the location of Igor's centre.

Just seen the satellite pics, in no way whatsoever is that a 45 MPH-looking system!

[Iceberg]

Igor is turning into a really interesting tropical storm. I think the NHC are spot on with their estimates re intensification, it does have a veyr large convective mass and so good outflow, however the centre has been continually sheared and the tracked centre has moved to the far north of the convective mass as the shear has moved from the east to the NE to the north, NHC are still saying 15kts of shear which is enough to prevent tightening of the system.

The bit in bold is the really interesting thing though as NHC are basically saying that it could have another LLCC in the deep convection, this would also help to limit current strengtening, but will make forecasting the storm difficult.

Motion is definately west atm and it looks like we will have to wait until later today to see Igor really ramp up as the shear should move readily away now.

CONVENTIONAL SATELLITE IMAGES INDICATE THAT IGOR IS MAINTAINING A

BURSTING PATTERN...CHARACTERISTIC OF A SHEARED TROPICAL CYCLONE.

THE PARTIALLY EXPOSED LOW-LEVEL CENTER LIES NEAR THE NORTHEAST SIDE

OF A LARGE AND CIRCULAR CONVECTIVE MASS IN THIS IMAGERY...BUT

SEVERAL EARLIER MICROWAVE OVERPASSES INDICATED THE POSSIBILITY OF

THE LOW-LEVEL CENTER LYING UNDERNEATH THE CONVECTION. AN EXPANDING

UPPER-LEVEL OUTFLOW IS WELL ESTABLISHED IN ALL QUADRANTS EXCEPT TO

THE EAST. DVORAK INTENSITY ESTIMATES ARE AT 3.0/45 KT AND 3.5/55

KT FROM SAB AND TAFB...AND THE LATEST 3-HOURLY AVERAGED ADT VALUE

IS 3.3. GIVEN THE UNCERTAINTY WITH REGARD TO THE LOCATION OF THE

CENTER...THE ADVISORY INTENSITY IS INCREASED CONSERVATIVELY TO 45

KT.

THE INITIAL MOTION ESTIMATE OF 285/18 IS SOMEWHAT UNCERTAIN AND

REPRESENTS A LONGER-TERM AVERAGE...GIVEN DIFFERENCES BETWEEN

CONVENTIONAL AND MICROWAVE SATELLITE FIXES. THE FORECAST REASONING

REMAINS UNCHANGED. DYNAMICAL MODELS SHOW IGOR MOVING ON A WESTWARD

COURSE ON THE SOUTH SIDE OF A SUBTROPICAL RIDGE OVER THE EAST

CENTRAL ATLANTIC DURING THE NEXT 72 HOURS. DURING THIS

PERIOD...THE MODEL GUIDANCE IS IN GOOD AGREEMENT THAT IGOR SHOULD

SLOW ITS FORWARD SPEED AND THEN TURN WEST-NORTHWESTWARD BEYOND 72

HOURS IN RESPONSE TO A LARGE BREAK IN THE SUBTROPICAL RIDGE OVER

THE WESTERN AND CENTRAL ATLANTIC. THE OFFICIAL NHC TRACK LIES NEAR

THE MIDDLE OF THE GUIDANCE ENVELOPE...BUT IS A BIT NORTH OF THE

MULTI-MODEL CONSENSUS WHICH HAS TRENDED SLIGHTLY SOUTHWARD THIS

CYCLE.

UW-CIMSS ANALYSES STILL INDICATE AROUND 15 KT OF NORTHEASTERLY

VERTICAL WIND SHEAR OVER IGOR...A LESS THAN IDEAL ENVIRONMENT FOR

INTENSIFICATION. THE STATISTICAL-DYNAMICAL GUIDANCE INDICATES A

QUICK REDUCTION TO THE SHEAR DURING THE NEXT 24 HOURS...AND A LOW

SHEAR ENVIRONMENT OVER GRADUALLY WARMER WATERS ARE LIKELY TO LEAD

TO A STEADIER STRENGTHENING OVER THE NEXT COUPLE OF DAYS. THE

INTENSITY GUIDANCE PRESENTS A DILEMMA LATER IN THE FORECAST

PERIOD...HOWEVER. THE STATISTICAL MODEL OUTPUT INDICATES POSSIBLE

SOUTHWESTERLY SHEAR RELATED TO THE LONGWAVE TROUGH FORECAST OVER

THE WEST CENTRAL ATLANTIC...AS DO A FEW OF THE GLOBAL DYNAMICAL

MODELS. ON THE OTHER HAND...THE HWRF AND ECMWF SOLUTIONS A

CONTINUATION OF THE LOW SHEAR ENVIRONMENT AND A STRONGER IGOR. THE

OFFICIAL NHC INTENSITY FORECAST IS ABOUT THE SAME AS THE PREVIOUS

ONE...EXCEPT SLIGHTLY REDUCED LATE IN THE PERIOD IN DEFERENCE TO

THE STATISTICAL MODELS.

[Iceberg]

Latest post eclipse imagery shows the centre nicely with very good banding and the shear lifting noticable even in the last two hrs, due to this we could see some rather rapid intensification later today possibly to just shy of hurricane. Going from this imagery the NHC idea of dual centres does not seem right.

ECM 00Z brakes from the models this morning and forces Igor up through the first ridge weakness, this brings him very quickly into our part of the atlantic just beyond the 240 range.

[Iceberg]

Looking at the loops and the eye like centre I would suggest this were a hurricane, IF it were not for the shear, however the shear is having the most effect in the NE quad exactly the area where you would expect the highest winds to be. Given this I would estimate a strength of 50-55kts, as the convection wraps around the eye and shear eases raising to a CAT 1 later this afternoon.

[AderynCoch]

Yes, the eye is starting to take shape and Igor is very nearly a hurricane (currently 70mph sustained winds). The intensity forecast has also been bumped up, calling for major hurricane status in 2-3 days.

[Gray-Wolf]

Certainly an 'eye like feature' but the NE quad is cloud stripped making for an odd shape. Once the shear there is overcome he'll look quite pretty (and big!) with a lot of ocean to trawl over.

[Jack Wales]

After presenting itself very well earlier, Igor is looking a bit ragged at the moment, suffering from what looks like strong north easterly shear which has left the LLC exposed to the north.

Igor also appears to have lost some of the strong convection we have observed over the last few days but this may be because the system is temporarily located within an envelope of dry air. Therefore I would not be surprised if the NOAA downgraded the intensity at the next advisory. Once the shear abates Igor should still become a hurricane in the next couple of days, however in order to do this vertically alignment of the centre needs to be established so that convection can really get going again.