Hurricane Irwin

[Somerset Squall]

Invest 97E has become Tropical Storm Irwin several hundred miles west of TD 10E. Intensity is 35kts. Irwin has some deepening central convection and well defined banding. There are even hints of an eye in satelite imagery. Irwin is forecast to strengthen initially, then maintain strength as shear begins to increase, in part due to the presence of TD10E to the east. Irwin may get close enough to 10E to interact with the system, but not close enough to be absorbed by it or to absorb it. Irwin is moving northwestwards but will soon turn to the northeast as the a trough picks up the storm.

Edited October 6, 2011 by Somerset Squall

[summer blizzard]

Irwin is definitely the bigger and more developed of the two and if anything seems to be acting like Ophelia on Phillipe already (feeding off the outer bands).

Both are moving WNW with 10E moving a little faster, so they are getting slightly closer however Irwin should be the slower and less developed of the two once 10E gets going as they both recurve at the same time which means that Irwin will trail 10E, that said some models do have Irwin as the more powerful hurricane upon landfall.

[Somerset Squall]

Irwin has strengthened to 50kts. The storm maintains excellent banding features. Irwin is now expected to become a hurricane over warm water and low shear, as TS Jova to the east is expected to have less of an impact on Irwin (Jova is now the weaker and smaller of the two storms).

[Cookie]

TROPICAL STORM IRWIN DISCUSSION NUMBER 3

NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011

200 PM PDT THU OCT 06 2011

WELL...SO MUCH FOR THE SLOW STRENGTHENING THAT WAS FORECAST IN THE

PREVIOUS ADVISORY. IRWIN HAS BECOME CONSIDERABLY BETTER ORGANIZED

OVER THE PAST SEVERAL HOURS...WITH WELL-DEFINED CURVED BAND

FEATURES WRAPPING AROUND THE CENTER. DVORAK INTENSITY ESTIMATES

RANGE FROM 45 TO 55 KT FROM SAB AND TAFB...RESPECTIVELY...AND THE

INITIAL WIND SPEED IS SET TO 50 KT. UPPER-LEVEL OUTFLOW HAS BECOME

BETTER-DEFINED AND IS EXPANDING. IT NOW APPEARS THAT...IN

COMPARISON TO THE TROPICAL CYCLONE LOCATED ABOUT 10 DEGREES TO THE

EAST...IRWIN IS THE DOMINANT SYSTEM. THIS IMPLIES THAT THE

CIRCULATION OF THE EASTERN CYCLONE WILL NOT HAVE MUCH OF AN ADVERSE

IMPACT...AND THE OFFICIAL FORECAST NOW SHOWS IRWIN STRENGTHENING

INTO A HURRICANE. THIS IS SIMILAR TO THE STATISTICAL-DYNAMICAL

GUIDANCE AND TO THE INTENSITY MODEL CONSENSUS.

THE STORM HAS MOVED A LITTLE FASTER TOWARD THE WEST-NORTHWEST...OR

295/7...OVER THE PAST FEW HOURS. A MID-LEVEL RIDGE TO THE

NORTHEAST OF IRWIN IS FORECAST TO RETREAT AS A DEEP-LAYER TROUGH

DEVELOPS TO THE NORTH OF THE TROPICAL CYCLONE. IN RESPONSE TO THIS

EVOLUTION OF THE STEERING PATTERN...IRWIN IS EXPECTED TO TURN

TOWARD THE RIGHT AND DECELERATE OVER THE NEXT COUPLE OF DAYS.

LATER IN THE FORECAST PERIOD...IRWIN SHOULD MOVE EAST-NORTHEASTWARD

TOWARD MEXICO IN THE FLOW TO THE SOUTH OF THE TROUGH. THE LATEST

OFFICIAL FORECAST IS A LITTLE FASTER THAN THE PREVIOUS ONE. THIS

IS BETWEEN THE SIGNIFICANTLY FASTER GFS...GFDL...AND HWRF GUIDANCE

AND THE SLOWER ECMWF FORECAST.

FORECAST POSITIONS AND MAX WINDS

INIT 06/2100Z 12.8N 117.9W 50 KT 60 MPH

12H 07/0600Z 12.9N 118.4W 55 KT 65 MPH

24H 07/1800Z 13.6N 118.5W 60 KT 70 MPH

36H 08/0600Z 13.9N 118.0W 65 KT 75 MPH

48H 08/1800Z 14.1N 117.4W 70 KT 80 MPH

72H 09/1800Z 14.5N 115.5W 80 KT 90 MPH

96H 10/1800Z 15.5N 113.0W 80 KT 90 MPH

120H 11/1800Z 16.5N 111.0W 80 KT 90 MPH

$$

FORECASTER PASCH

[summer blizzard]

http://www.ssd.noaa....lt/t6/ir2-l.jpg

Wow, less than 24 hours after being named and Irwin is pretty much a hurricane.

EDIT: We have an eye!!

Edited October 7, 2011 by summer blizzard

[Somerset Squall]

Irwin is now a 75kt, cat 1 hurricane. Irwin had a well defined eye earlier today but it has become cloud obscured this evening. Irwin is expected to continue to strengthen for the next 48hrs and then weaken as shear increases. The turn towards the east is expected to begin soon.

[summer blizzard]

Jova and Irwin have both made the turn and as a result Irwin is now the secondary storm being sheared, Irwin is now a 70mph Tropical Storm and i suspect that intensity may be fairly stagnant for the next 3 -4 days before it strengthens again as it approaches the coast.

The slower Irwin is relative to Jova, the stronger he shall be.

[Somerset Squall]

Indeed SB, the interaction between these two storms has been interesting. When Jova was following Irwin, Jova was the weaker of the two. Now Irwin is following Jova to the east, he is the weaker of the two. The hurricane peaked at 80kts before Jova sheared Irwin, and the intensity has fallen back to a very modest 40kts. Little or no convection resides over Irwin's LLC, and is confined to a band south of the centre. The storm could degenerate into a remnant low if convection doesn't come back- a distinct possibility given the continued shear in the wake of Hurricane Jova and also the dry, stable air been entrained into Irwin's circulation from the north. Even if this does occur, Irwin could redevelop in a few days time as shear lessens (Jova will be inland and weakening at this point) and sea temps increase near the coast of Mexico. Irwin could hit a very similar area of coast to Jova, so needs to be closely watched.

[Somerset Squall]

Irwin has saved itself by wrapping the convection in the southern band over the LLC. The environment ahead of Irwin is marginal at best in Jova's wake however, so very little strengthening is forecast until Irwin nears the coast of Mexico in 5/6 days time.

[Somerset Squall]

Convection has weakened significantly again in association with Irwin this morning. Easterly shear continues to plague the storm, and dry/stable air continues to affect Irwin from the north. As long as this environment persists, Irwin will remain a weak tropical storm or even degnerate into a remnant low. The storm continues eastwards in Jova's wake, and this motion is expected to persist over the next few days. By day 4/5, things become more uncertain. Fujiwhara Interaction could still occur as Irwin moves around the south side of a weakening Jova (Jova will be over land at this point). A second scenario is that a weak and shallow Irwin could turn southeastwards away from the Mexican coast in low level steering flow. A very interesting system if the second scenario unfolds, it's not often you get a southeastward moving cyclone in the East Pacific!

[Somerset Squall]

Irwin is hanging on for dear life as it continues eastwards. Intensity is 35kts. Irwin has actually put up an impressive burst of convection over the last 6 hours, but this will probably dissipate soon as shear and dry air continue to plague the storm.

Look at the track map above, a very odd track for an East Pacific tropical cyclone!

Edited October 11, 2011 by Somerset Squall

[summer blizzard]

http://www.ssd.noaa.gov/goes/flt/t6/vis-l.jpg

Tropical Storm Irwin is actually looking pretty good tonight as Jova is on a different heading. I suspect that over the next 48 hours we may see Irwin becoming a decent strength however it does seem shear will arrive to kill it off afterward.

The track is such because Irwin is so weak and as a result is being driven by low level steering currents.

[Somerset Squall]

Irwin has fluctuated between depression and storm strength over the last day or so, governed by flaring and dissipating convection. The storm has continued on a unusually persistant eastward track. With Jova gone, Irwin has found himself in a lower shear environment, and is currently a 35kt tropical storm. The storm is near the coast of Mexico, but it shouldn't cause too many problems. Irwin's bizarre track will send the storm southwards and then westwards as the storm completes a clockwise loop and then feels the influence of newly bulit ridging to the north. Aside from some dry air, the environment appears favourable, and as Irwin dips southwards into warmer waters again, it may strengthen beyond the 40kts forecasted by the NHC. NHC are being cautious at present as some models still insist on dissipating the storm.

Track demonstating Irwin's unusual track (the majority of East Pacific storms head west-northwestwards throughout their lifetime):

[Cookie]

Very erratic track, defiantly a drunken System!

[summer blizzard]

http://moe.met.fsu.edu/~acevans/models/ep112011_inten.png

Yes, it should should be noted that a large group of models take him near hurricane strength.

Given his persistence and a generally good environment ahead, i expect him to regain hurricane status.

[Somerset Squall]

Irwin has remained in a fairly steady state over the last 24hrs, and has intensified slightly to 40kts. Though shear is low and waters warm, the air surrounding Irwin is dry, which is stopping the storm from intensifiying significantly. Little change in strength is expected for the next 48hrs, followed by some weakening as shear rises and Irwin moves over waters cooled by Jova earlier in the week. The southward motion has started this evening, but the track should bend to the west soon as ridging over Baja California takes control of the steering pattern. NHC mention this ridge will break down in 4/5 days time, which means Irwin will stall at this time. It's difficult to tell how much of Irwin will be left at this point. Irwin has certainly shown that it can survive hostile conditions, but will elevated shear AND cooler waters upwelled by Jova be finally enough to kill the storm?

[Somerset Squall]

Irwin has moved southwards through the day but is now moving southwestwards. The storm will veer to the west as the ridging to the north gains full control of the steering flow for Irwin. Irwin is struggling at the moment with moderate northeasterly shear, and also passage over cool waters upwelled by Jova. Intensity has fallen to 35kts. The LLC is partially exposed to the northeast of a shrinking area of convection. If current convective trends persist, then Irwin may degnerate to a remnant low pretty soon. The environment is expected to remain far from ideal over the coming days, which should finally put a nail in the coffin for this very tenacious storm.

[Somerset Squall]

Irwin has moved southwestwards out of the cold wake of Jova and over waters of 29C. As a consequence, convection has refired over the LLC today despite continued high shear. Intensity has fallen to 30kts making Irwin a depression. Shear is set to rise further so the forecast is for Irwin to degenerate into a remnant low in about 36hrs. Any reduction in shear however, may be enough to allow Irwin to survive longer as waters are very warm along track.

[Somerset Squall]

Irwin degenerated into a remnant low yesterday. Regeneration is not expected to to high shear and dry air.