WunderBlog Archive » Category 6™
Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.Tropical Storm Dolly Hits Mexico; Tropical Storm Norbert Threatening Baja
Tropical Storm Dolly made landfall on Mexico's Gulf of Mexico coast just south of Tampico near 11 pm EDT Tuesday night as a minimal tropical storm with 45 mph winds. While Dolly's winds will not cause major damage, the storm's rainfall has the potential to cause dangerous flash flooding and mudslides as Dolly pushes inland and dissipates today. Radar-estimated rainfall from the Brownsville, Texas radar showed areas of 2 - 4 inches of rain along the coast of Mexico as of Wednesday morning, and isolated rainfall amounts of up to 15" are expected from Dolly. Satellite loops on Wednesday morning showed that Dolly still had some very heavy thunderstorms over the warm waters just offshore from Tampico, though the storm had been downgraded to a tropical depression with 35 mph winds as of 7 am CDT on Wednesday.
Figure 1. Twin tropical storms besiege Mexico: Tropical Storm Dolly nears landfall along Mexico's Bay of Campeche (right) as Tropical Storm Norbert brushes the Pacific coast of Southwest Mexico (left) in this GOES-East image taken at 7:45 pm EDT September 2, 2014. At the time, both storms had 45 mph sustained winds. Image credit: NASA/Goddard Space Flight Center.
Figure 2. Radar-estimated rainfall from the Brownsville, Texas radar as of 9:49 am EDT on September 3, 2014, showed areas of 2 - 4" of rain had fallen along the coast of Mexico.
Tropical Storm Norbert a threat to Baja Mexico
In the Eastern Pacific, Tropical Storm Norbert is approaching hurricane strength in the waters south of the Baja Peninsula, taking advantage of unusually warm 29.5°C (85°F) Sea Surface Temperatures (SSTs.) These SSTs are about 2°C (3.6°F) warmer than average. Satellite loops on Wednesday morning showed that Norbert had developed some very intense eyewall thunderstorms with cold cloud tops, and microwave imagery showed an eye beginning to develop. Norbert should be able to take advantage of warm SSTs, a moist atmosphere, and moderate wind shear over the next two days to intensify into at least a Category 1 hurricane. The 5 am PDT run of the SHIPS model predicted a substantial 30% chance that Norbert could undergo rapid intensification from a tropical storm with 60 mph winds to a Category 2 hurricane with 100 mph winds by Thursday morning. However, Norbert is a small storm, and it's hurricane-force winds are only expected to reach out about 20 - 25 miles from the center when it makes its closest pass by the tip of the Baja Peninsula on Thursday night and Friday morning. In their 2 am PDT WInd Probability Advisory, NHC gave Cabo San Lucas on the southern tip of the Baja Peninsula a 72% chance of experiencing tropical storm-force winds of 39+ mph, and a 10% chance of experiencing hurricane-force winds of 74+ mph.
Figure 3. MODIS true-color image of a well-organized tropical wave preparing to move off the coast of Africa, at approximately 8 am EDT September 3, 2014. Image credit: NASA.
New African tropical wave this weekend may develop
A tropical wave is expected to come off the coast of Africa on Thursday and move to the west at about 15 mph. This wave will be capable of bringing heavy rain and strong winds to the Cape Verde Islands on Friday and Saturday. Two of our three reliable computer models for predicting tropical storm formation show development by Sunday of the wave, and in their 8 am EDT Wednesday Tropical Weather Outlook, NHC gave the system 2-day and 5-day odd of development odds of 0% and 30%, respectively. The Wednesday morning runs of the GFS and European ensemble models favored the storm taking a more west-northwesterly track into the open ocean next week, with a low long-range threat to the Lesser Antilles Islands indicated. However, it is too early to be confident that the storm will miss the islands, as the long-range tracks have shifted closer to the Lesser Antilles since their runs on Tuesday. The Atlantic is expected to be dominated by dry, sinking air next week, due to the phase of the Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days, so I expect that any tropical waves crossing from Africa towards the Lesser Antilles will struggle to develop.
Jeff Masters
Figure 1. Twin tropical storms besiege Mexico: Tropical Storm Dolly nears landfall along Mexico's Bay of Campeche (right) as Tropical Storm Norbert brushes the Pacific coast of Southwest Mexico (left) in this GOES-East image taken at 7:45 pm EDT September 2, 2014. At the time, both storms had 45 mph sustained winds. Image credit: NASA/Goddard Space Flight Center.
Figure 2. Radar-estimated rainfall from the Brownsville, Texas radar as of 9:49 am EDT on September 3, 2014, showed areas of 2 - 4" of rain had fallen along the coast of Mexico.
Tropical Storm Norbert a threat to Baja Mexico
In the Eastern Pacific, Tropical Storm Norbert is approaching hurricane strength in the waters south of the Baja Peninsula, taking advantage of unusually warm 29.5°C (85°F) Sea Surface Temperatures (SSTs.) These SSTs are about 2°C (3.6°F) warmer than average. Satellite loops on Wednesday morning showed that Norbert had developed some very intense eyewall thunderstorms with cold cloud tops, and microwave imagery showed an eye beginning to develop. Norbert should be able to take advantage of warm SSTs, a moist atmosphere, and moderate wind shear over the next two days to intensify into at least a Category 1 hurricane. The 5 am PDT run of the SHIPS model predicted a substantial 30% chance that Norbert could undergo rapid intensification from a tropical storm with 60 mph winds to a Category 2 hurricane with 100 mph winds by Thursday morning. However, Norbert is a small storm, and it's hurricane-force winds are only expected to reach out about 20 - 25 miles from the center when it makes its closest pass by the tip of the Baja Peninsula on Thursday night and Friday morning. In their 2 am PDT WInd Probability Advisory, NHC gave Cabo San Lucas on the southern tip of the Baja Peninsula a 72% chance of experiencing tropical storm-force winds of 39+ mph, and a 10% chance of experiencing hurricane-force winds of 74+ mph.
Figure 3. MODIS true-color image of a well-organized tropical wave preparing to move off the coast of Africa, at approximately 8 am EDT September 3, 2014. Image credit: NASA.
New African tropical wave this weekend may develop
A tropical wave is expected to come off the coast of Africa on Thursday and move to the west at about 15 mph. This wave will be capable of bringing heavy rain and strong winds to the Cape Verde Islands on Friday and Saturday. Two of our three reliable computer models for predicting tropical storm formation show development by Sunday of the wave, and in their 8 am EDT Wednesday Tropical Weather Outlook, NHC gave the system 2-day and 5-day odd of development odds of 0% and 30%, respectively. The Wednesday morning runs of the GFS and European ensemble models favored the storm taking a more west-northwesterly track into the open ocean next week, with a low long-range threat to the Lesser Antilles Islands indicated. However, it is too early to be confident that the storm will miss the islands, as the long-range tracks have shifted closer to the Lesser Antilles since their runs on Tuesday. The Atlantic is expected to be dominated by dry, sinking air next week, due to the phase of the Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days, so I expect that any tropical waves crossing from Africa towards the Lesser Antilles will struggle to develop.
Jeff Masters
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