Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 3:25 PM GMT on August 19, 2014
A tropical wave located in the Central Atlantic near 11°N 48°W, about 1,000 miles east of the Lesser Antilles Islands, is headed westwards at about 10 mph. Satellite loops show the wave has a broad, elongated surface circulation and a small amount of heavy thunderstorm activity that is poorly organized. Wind shear is moderate, 10 - 20 knots, and water vapor satellite images and the Saharan Air Layer analysis show that the wave is surrounded by dry air, though the amount of dryness has lessened over the past two days. Sea Surface Temperatures (SSTs) are marginal for development, about 27°C. The Tuesday morning run of one of our three reliable models for predicting tropical cyclone genesis, the UKMET model, did show this wave developing into a tropical storm on Friday as it passed through the Lesser Antilles. Given the presence of so much dry air near the disturbance, the risk of development is low Tuesday and Wednesday, but development odds will increase on Thursday as the wave nears the Lesser Antilles, where ocean temperatures will be warmer and the atmosphere a little moister. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC gave the disturbance 2-day and 5-day development odds of 10% and 20%, respectively. The Hurricane Hunters are on call to investigate the disturbance on Thursday afternoon, if necessary.
A second disturbance near 13°N, 37°W, midway between Africa and the Lesser Antilles Islands, also has a small area of disorganized heavy thunderstorms with some modest rotation. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC gave this disturbance 2-day and 5-day development odds of 10% and 20%, respectively. None of our three reliable models for predicting tropical cyclone genesis predict that this disturbance will develop over the next five days as it heads west-northwest at about 10 mph.
Figure 1. Tropical Storm Lowell as seen at 11 am EDT Tuesday, August 19, 2014. At the time, Lowell had top winds of 50 mph. Image taken from a super-rapid scan mode loop from the NOAA/RAMMB website.
The Eastern Pacific heating up
In the Eastern Pacific, we have a new named storm, Tropical Storm Lowell, which formed at 03 UTC on Tuesday. The GOES-West satellite is in super-rapid scan mode over Lowell today, and you can access some very impressive one-minute time resolution loops of Lowell at the NOAA/RAMMB website. Lowell's formation gives the Eastern Pacific 12 named storms, 6 hurricanes, and 5 intense hurricane so far this season. On average, the Eastern Pacific sees 8 named storms, 4 hurricanes, and 1 intense hurricane by August 18, so it has been a very active year in the basin. Tropical Storm Karina is also spinning away in the Eastern Pacific today, and Karina and Lowell are expected to become entangled with each other early next week and die in the cool waters well to the west of Baja Mexico. The models have been consistently predicting that a another named storm (Marie) will form late this week from a tropical wave that crossed Central America on Monday and will move parallel to the Mexican coast a few hundred miles offshore. This storm, which NHC is giving 5-day odds of development of 70%, is something residents of the Baja Peninsula should monitor next week. Ocean temperatures in the waters just west of the Baja Peninsula are unusually warm---30°C (86°F), which is about 3°C (5°F) above average--so Marie will have plenty of heat energy available to power it.
The Western Pacific remains mercifully quiet, with no new named storms expected to develop over the next five days.
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