Lots of disturbances, but not much threat

You can tell it's getting near peak hurricane season, since we are tracking four separate areas of disturbed weather that NHC has labeled as "Invests." None of these disturbances are a major concern at present, but we will need to watch them closely.

Not much has changed from yesterday with 94L, the tropical wave about 600 miles east of the Lesser Antilles Islands. The wave has slowed down its forward speed to 10-15 mph, so should be entering the islands on Saturday, bringing gusty winds and heavy rain. QuikSCAT data from last night showed that the storm became less organized yesterday, with a weak, elongated circulation. Top winds were 20 knots (23 mph). Visible satellite loops show a limited amount of disorganized thunderstorm activity. Wind shear is still a favorable 5-10 knots over 94L, and may decrease some by Saturday, allowing a better chance for development. It looks like 94L will stay well south of the shearing winds of the upper-level low spinning north of Puerto Rico.

The presence of a large, dusty area of dry air surrounding its north side continues to cause major problems for 94L. Once again today, this dry air is being sucked into 94L's thunderstorms. This dry air is creating strong downdrafts visible as arc-shaped surface cumulus clouds along the ocean surface. The presence of these arc-shaped surface clouds is usually a good sign that a storm is struggling with dry air and will not intensify significantly for at least the next 12 hours.

Water vapor satellite loops of the region show that 94L has not significantly moistened its environment. As the storm continues further west, it may be able to gradually do so, allowing it more of a chance to get organized. None of the reliable computer models forecast that 94L will develop into a tropical depression. The Hurricane Hunters are scheduled to investigate this system on Friday afternoon.


Figure 1. Infrared satellite image showing the various disturbed area of weather in the Atlantic today.

95L and 96L
An area of low pressure ("95L") about 400 miles east of Jacksonville, Florida has an elongated, closed circulation, but very little heavy thunderstorm activity. A separate low ("96L") is about 400 miles east of Cape Hatteras, North Carolina, and has a well defined closed circulation with plenty of heavy thunderstorm activity. QuikSCAT data from 6:08am EDT this morning shows this circulation nicely. Top winds seen by QuikSCAT were 30 knots (35 mph). Wind shear over both disturbances was 10-20 knots, and some development of both systems is possible today. It appears now that the North Carolina disturbance, 96L, is becoming the dominant system, which will make 95L's development slow, since the two systems are so close together. We can pretty much throw out the model predictions for these disturbances, since none of the models properly initialized two low pressure systems in this region. 96L (the North Carolina low) has developed some upper level outflow and low-level spiral bands, and this storm may become a tropical depression today or tomorrow. It should get caught up in the jet stream and whisked out to sea to the northeast, and at present does not appear to be a threat to any land areas except the Canadian Maritime provinces.

It is possible 96L will grow into a strong tropical storm who's outflow will choke off and kill 95L. If 95L survives, it may have a chance to develop into a tropical depression once 96L vamooses. It is less clear what the track of 95L might be, since it is further south where steering currents are weak. I expect 95L may wander erratically for a few days.

There is a Hurricane Hunter mission scheduled for this afternoon to investigate 96L. No missions are scheduled for Friday into this system.

Mexico is watching 97L
An area of low pressure ("97L") is bringing heavy rains to the same part of the Mexican coast inundated by Hurricane Dean. 97L has only about 12 more hours over water before it moves ashore, but may become organized enough to become a tropical depression before doing so.

Coast of Africa
None of the computer models are forecasting the development of a tropical depression during the coming week off the coast of Africa. There is a large surge of moisture with tropical waves embedded in it coming off the coast of Africa this week, so we will need to continue to monitor this area for development.

Jeff Masters