eastern pacific Major Hurricane Blanca

[Somerset Squall]

The second tropical depression of the season has formed from Invest 93E, and is located south of Zihuatanejo, Mexico. 02E has a small LLC, with some persistant deep convection. Outflow from Major Hurricane Andres to the west is imparting some shear on 02E, which should prohibit much strengthening over the next day. As Andres moves away and weakens, shear should ease over 02E, allowing intensification. NHC expect 02E to be a 90kt hurricane in 5 days time.

 

The steering pattern is unusually complex. A building ridge to the west of 02E will likely force the depression to take an unusual southward motion over the next day or two, before ridging rebuilds to the north and sends 02E back to a more typical west-northwesterly track.

[Somerset Squall]

Tropical Depression 02E has become Tropical Storm Blanca, with winds of 35kts. Convection has increased greatly over the LLCC, with deep convective bands wrapping into the circulation. Shear is easing, and Blanca seems poised for further intensification. The storm is stalling, and just a very slow southwestward drift is expected over the next couple days, followed by a faster northwestward motion.

[Somerset Squall]

After a period of arrested development due to moderate shear, Blanca now appears to be rapidly intensifying. Winds are up to 55kts, and the storm now has a well developed central dense overcast with tight banding wrapping in. With very low shear, good outflow, warm water and high moisture present in the region of Blanca, the storm should continue to rapidly intensify. NHC expect Blanca to peak at 120kts.

[Somerset Squall]

Blanca has become a hurricane with winds of 65kts. Further rapid intensification is expected. Blanca remains almost stationary at present, and will probably remain so for another 36hrs or so, before ridging to the northeast sends Blanca northwestwards at a faster speed, towards the southern tip of Baja California. It is too early to say whether landfall will occur, but the current track forecasts a landfall.

[Somerset Squall]

Blanca continues to rapidly intensify. Winds are up to 95kts in the latest NHC update. Blanca has developed a pinhole eye, a sign of an intense system. NHC expect a peak of 130kts now, I wonder if we can squeeze out a cat 5?

[Somerset Squall]

Blanca has become a category 4 major hurricane with winds of 115kts. This is the earliest second major hurricane on record. And another cat 4, forecast to be a cat 5 soon. The Eastern Pacific is on fire!

[Somerset Squall]

Due to Blanca stalling for so long, upwelling of colder waters has occurred, and this, along with an eyewall replacement cycle, has caused Blanca to weaken considerably today, instead of strengthening. Winds are down to 85kts, cat 2. When Blanca finally moves, it will move back over warm water and should regain a little strength, but NHC only expect a smaller 95kt second peak in intensity.

[Somerset Squall]

Blanca weakened to 80kts but has since restrengthened a little to 85kts as it has finally started moving northwestwards back over warmer waters. The eye is pretty ragged, and the convection is still a little asymmetric, and as Blanca probably has less than 24hrs before it moves over cooler water and higher shear, it probably won't make major hurricane (cat 3 and above) status again. The southern tip of Baja California still looks to be in the firing line of tropical storm conditions as Blanca approaches as a weakening storm.

[Somerset Squall]

Both Andres and Blanca's intensity forecasts have been particularly challenging, with big errors even from NHC. They did not forsee the weakening that Blanca experienced when stalled, neither have they foreseen the rapid strengthening Blanca has undergone today. Winds are back up to 115kts, cat 4 on the SS scale. The eye is much better defined, surrounded by intense and more symmetrical convection. A little further intensification cannot be ruled out, but Blanca will weaken on approach to Baja California.

[Vorticity0123]

Both Andres and Blanca's intensity forecasts have been particularly challenging, with big errors even from NHC. They did not forsee the weakening that Blanca experienced when stalled, neither have they foreseen the rapid strengthening Blanca has undergone today. Winds are back up to 115kts, cat 4 on the SS scale. The eye is much better defined, surrounded by intense and more symmetrical convection. A little further intensification cannot be ruled out, but Blanca will weaken on approach to Baja California.

Yes, the NHC has had a tough time so far with these two tropical cyclones. The past intensity of Blanca (given by the black line in the image below) has been rather irregular to say the least. As a rough approximation, five different stages have been distinguishable for now, including:

 

1) Gradual organisation of Blanca from its birth up to about midway on June 2.

 

2) Accelerated intensification of the cyclone up to midway June 3, showing an increase of 65 kt in only 24 hours (!). This seems to have been associated with a patch of very warm water over which Blanca stalled for a prolonged period of time. At its peak, the cyclone had a quite small eye.

 

3) Weakening due to cool water upwelling after stalling over too many days. During this phase (lasting to 00UTC June 5), convection (especially eyewall convection) weakened significantly and the eye expanded greatly in size. The NHC anticipated that after this phase (when Blanca moved away from the cool waters) only slight strengthening would occur due to the complex structure, but truth was different.

 

4) Renewed organization and intensification on June 6 up to midway June 7. Unexpectedly, the cyclone reorganized rather quickly, developing vigorous eyewall convection along with a slight contraction of the eye itself.

 

5) Weakening as Blanca moved over cooler waters and into an increased shear environment. That is where we are now. Most likely, the storm will impact Baja California as a weakening tropical storm before dissipation.

 

Satellite intensity estimates and best track intensities (from NHC, in black) of Blanca.

 

For now, a rapid demise of Blanca appears to be inevitable, as the eye is no longer visible. Furthermore, the convection is stripped away to the northwest caused by southwesterly shear. Cooler waters are also having a negative impact on the cyclone.

 

Satellite image of Blanca, showing the remains of an eye on the southeastern edge of the convection.

 

Sources:

http://tropic.ssec.wisc.edu/#

http://www.ssd.noaa.gov/PS/TROP/floaters/02E/02E_floater.html

http://www.nhc.noaa.gov/

Edited June 7, 2015 by Vorticity0123

[Somerset Squall]

Good summary there Vorticity . Blanca certainly has been an irregular tropical cyclone, and not just for intensity, but also for track. It has been confirmed that Blanca is the first tropical cyclone on record to make landfall on Baja California before July. It's track is more typical of a later season cyclone (ie September/October), a track such as Blanca's is not at all normal for June.