Norbert Hits Category 3; Three Minor Atlantic Threat Areas to Watch
By: Jeff Masters , 4:13 PM GMT on September 06, 2014
Hurricane Norbert put on an unexpected burst of rapid intensification overnight, topping out as a Category 3 storm with 120 mph winds at 5 am EDT Saturday. Norbert continues to chug parallel and just offshore from the coast of Mexico’s Baja Peninsula, bringing heavy rain and tropical storm-force winds to the coast. Satellite loops on Saturday morning showed that Norbert had a small eye and some very impressive eyewall thunderstorms with cold cloud tops. However, the storm is starting to weaken, thanks to cooler ocean temperatures near 27°C (81 °F), and drier air. The models all show the core of the hurricane remaining just offshore as it moves northwest parallel to the Baja Peninsula over the next three days, so heavy rains of 3 – 6″ causing flash flooding will be the primary threat from Norbert to Baja. The counter-clockwise flow of air around the hurricane is pulling moisture from the remnants of Tropical Storm Dolly and from the tropical Eastern Pacific northwards into Northern Mexico and the Southern Arizona, and this moisture will be capable of causing flooding rains in those regions.
Norbert’s intensification into a Category 3 storm gives the Eastern Pacific seven major hurricanes so far this year. With the season typically only 2/3 over by September 9, we have a decent chance of tying or beating the record of ten intense hurricanes in a season, set in 1992 (this tally includes hurricanes in the Central Pacific.) The 2014 tally for the Eastern Pacific currently stands at 14 named storms, 10 hurricanes, and 7 intense hurricanes. An average Eastern Pacific hurricane season sees 15 named storms, 8 hurricanes, and 3 intense hurricanes during the entire year. The records for total number of named storms, hurricanes, and intense hurricanes were all set in 1992, with 28 named storms, 16 hurricanes, and 10 intense hurricanes (with the Central Pacific tallies included.)
Figure 1. Hurricane Norbert near Mexico’s Baja Peninsula at 10:30 am EDT September 6, 2014. At the time, Norbert was a Category 3 storm with 115 mph winds. Image credit: NASA/GSFC.
Figure 2. Predicted seven-day precipitation amounts for the period ending on Saturday, September 13 show a large area of 3+ inches are expected over Southeast U.S., thanks to a weak tropical disturbance. A region of 2+” of rain is expected over Southern Arizona due to the flow of moist air northwards caused by Hurricane Norbert’s circulation. Image credit: NOAA/HPC.
Southeast U.S. disturbance bringing heavy rains
A weak area of low pressure near the coast of Georgia is bringing heavy rain showers to the Southeast U.S. coast and adjacent waters, but this this activity is very disorganized. The disturbance will bring heavy rains in excess of three inches to the coast over the next few days as the low drifts northeastward. After that time, the low will likely merge with a frontal zone over the ocean and head out to sea. In their 8 am EDT Saturday Tropical Weather Outlook, NHC gave the system 2-day and 5-day odd of development odds of 0% and 10%, respectively.
Tropical Wave 90L
A tropical wave (90L) located a few hundred miles west of the Cape Verde Islands is headed west to west-northwest at about 15 mph. Satellite images show 90L has plenty of spin, but little heavy thunderstorm activity. Though Sea Surface Temperatures are fairly warm, 27.5°C (82°F), and wind shear is low, 90L is embedded in a very dry air mass that is expected to get dryer as the storm progresses westwards. None of our three reliable computer models for predicting tropical storm formation predicts development of 90L over the next five days. In their 8 am EDT Saturday Tropical Weather Outlook, NHC gave the system 2-day and 5-day odd of development odds of 10%. The wave should arrive in the northern Lesser Antilles Islands by Wednesday night.
New African Tropical Wave
Following on the heels of 90L will be a new tropical wave that is expected to push off the coast of Africa on Sunday night or Monday morning, bringing heavy rain showers and gusty winds to the Cape Verde Islands on Monday and Tuesday. All three of our three reliable computer models for predicting tropical storm formation show development of the new wave by Wednesday. The new wave will see similar conditions to 90L, though, and will struggle with dry air and moderate wind shear. In their 8 am EDT Saturday Tropical Weather Outlook, NHC gave the system 2-day and 5-day odd of development odds of 0% and 30%, respectively. The wave should take a more northwesterly track then 90L, and not threaten the Lesser Antilles Islands.