Major Hurricane Miriam

[Somerset Squall]

The thirteenth tropical depression of the East Pacific season has formed well southwest of Manzanillo, Mexico. The depression looks to be on the verge of becoming a tropical storm as convection continues to increase over the LLC, and banding features become better defined. Low shear and warm sea temps should allow 13E to strengthen over the next few days before the cyclone gets pulled northwards into colder waters.

Edited September 22, 2012 by Somerset Squall

[Somerset Squall]

Tropical Depression 13E has been upgraded to Tropical Storm Miriam, with sustained winds now of 35kts. Miriam is a well organised tropical storm with deep convection over the LLC and pronounced banding features in both the north and south quadrants. SHIPS rapid intensification index indicates a high chance of rapid intensification over the next 24hrs, with a 25-30kt intensity gain possible in this time. This seems reasonable given the increasingly well defined inner core and strong banding, and the fact that Miriam is in a very low shear environment with very warm waters beneath the storm.

[Somerset Squall]

Miriam has strengthened quickly. Sustained winds are now 55kts, and it shouldn't be long before Miriam becomes a hurricane. Shear is low, waters are warm and there is abundant moisture available for Miriam to tap into. NHC say that the SHIPS rapid intensification index indicates a 75% chance of a 30kt increase in strength in the next 24hrs. Miriam has a solid central dense overcast so seems poised for further intensification.

[Somerset Squall]

Scrap a 30kt increase, Miriam has gone further than that. Miriam has rapidly intensified overnight and is now a 90kt category 2 hurricane. Miriam may not be done with this rapid intensification phase, and could become a major hurricane this afternoon. NHC mention the possibility of Miriam attaining category 4 intensity as a very real one. The well organised hurricane sports a small, well defined eye. This has "major hurricane" written all over it IMO, as Miriam has another 24hrs to strengthen, perhaps rapidly.

[Coast]

Forecasters: Miriam strengthens into a Category 2 hurricane well off Mexico’s Baja peninsula

MIAMI — U.S. forecasters say Miriam has rapidly strengthened into a Category 2 hurricane well off Mexico’s Baja California peninsula, but poses no threat to land.

Forecasters at the National Hurricane Center in Miami said Miriam is packing top sustained winds of 105 mph (165 kph) and could become a major hurricane sometime later Monday. The hurricane formed a day earlier in the eastern Pacific and at 5 a.m. EDT was centered about 415 miles (665 kms) south-southwest of the southern tip of Baja California. The center says Miriam was moving northwest near 13 mph (20 kph). No coastal watches or warnings are in effect.

In the open Atlantic, Tropical Storm Nadine weakened somewhat early Monday while meandering far from land. It had sustained winds of about 50 mph (85 kph).

http://www.washingtonpost.com/national/forecasters-say-hurricane-miriam-has-formed-in-the-pacific-ocean-no-threat-to-land/2012/09/23/ec1d7f6c-05f3-11e2-9eea-333857f6a7bd_story.html

[Somerset Squall]

Miriam has become a major hurricane, with sustained winds now at 105kts. Currently, Miriam is the second strongest East Pacific hurricane of the year, behind Emilia. Miriam has developed a pinhole eye, a sure sign of an intense system. Miriam may strengthen a little more over the next 24hrs, before shear slowly increases and sea temps cool as the track bends towards the north. Cat 4 is not out of the question.

[Somerset Squall]

Miriam began an eyewall replacement cycle (EWRC) shortly after I posted which stopped further strengthening. Miriam has struggled to complete this cycle, and has weakened to 85kts, a cat 2 hurricane. Although Miriam is has nearly completed the EWRC, further weakening is expected as the northward track takes Miriam over cooler waters and increasing westerly shear. Miriam is expected to continue heading northwards just west of Baja California. Increased moisture associated with Miriam may increase shower activity here over the coming days.

[Somerset Squall]

Miriam is weakening fairly swiftly, helped on by increased shear as well as cooling sea temps. Intensity is down to 50kts. As Miriam continues to gain lattitude, it will weaken further as the hostile environment persists. NHC are forecasting Miriam to degenerate into a remnant low by 48hrs time, and there's a possibilty of this occuring sooner.

[Coast]

U.S. forecasters say Tropical Storm Miriam is fast weakening off Mexico's Baja California peninsula.

The National Hurricane Center in Miami said that Miriam had top sustained winds of 45 mph (72 kph) at 11 p.m. EDT Wednesday, down sharply from a day earlier when it was a hurricane. The storm is centered about 385 miles (620 kilometers) west-southwest of the southern tip of the Baja peninsula.

Miriam is moving northwest at 7 mph (11 kph). No coastal watches or warnings are in effect and more weakening is expected.

In the eastern Atlantic, Tropical Storm Nadine lingered far from land. It is about 640 miles (1030 kilometers) south-southwest of the Azores islands with top sustained winds of about 50 mph (80 kph), and is moving southwest at 6 mph (10 kph).

http://abcnews.go.com/International/wireStory/tropical-storm-miriam-quickly-weakening-off-mexico-17334718#.UGRcOrJlREM