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91E and 92E over the Pacific; long-range development possible over the Caribbean

By: Civicane49 , 9:19 AM GMT on May 27, 2013

A weak area of low pressure (Invest 91E) that has persisted over the eastern Pacific in the past few days is currently located about 600 miles southwest of Manzanillo, Mexico. This system has not changed much in organization today as convection remains disorganized on satellite images. The latest surface analysis show 91E remaining embedded along the monsoon trough/Intertropical Convergence Zone (ITCZ). The system’s interaction with it will make it difficult to become a tropical cyclone. Moderate easterly shear is also affecting the system and has shifted the small area of deep convection away from a defined low-level center, which is now exposed.

Forecast for 91E
Further development of 91E is slim as conditions will slowly become more hostile for development in the coming days. In fact, the SHIPS model is anticipating the easterly shear to increase over 91E by day three. The attachment with the monsoon trough/ITCZ makes it hard for the low to develop and should remain embedded in the next few days. In addition, dry air to the north of the disturbance would intrude into the system and cause limited convective activity. I give this system a 10% chance of becoming a tropical cyclone in the next 48 hours. 91E is anticipated to move slowly westward over the eastern Pacific in the next several days before moving to the east and being absorbed by the secondary system.

Figure 1. Morning infrared satellite image of Invest 91E located southwest of the Mexican coast. Image credit: Mauna Kea Weather Center (MKWC).

Invest 92E continuing to organize
Another area of low pressure (Invest 92E) located south of the Gulf of Tehuantepec is continuing to show signs of organization; deep convection has maintained over the past several hours as the system continues to consolidate and moves west-northwestward. The low-level center of the system is currently beneath the main area of deep convection. Satellite imagery and surface analysis indicate that the system remains embedded along the monsoon trough. The system’s interaction with it would make development slow to occur as the low must gather strength and organization to break free from it and can then become a tropical cyclone. However, it is in the process of detaching itself as the system is gaining some latitude over the past several hours.

Forecast for 92E
I foresee 92E continuing to organize in the next couple of days and become a tropical depression by Tuesday or so. Situating in an extremely conducive environment with very warm sea surface temperatures, low vertical wind shear, moist atmospheric environment, and good outflow pattern, I see no reason why the system should not continue to organize and become a tropical cyclone in the next couple of days. Although the system remains embedded along the monsoon trough, it appears to be in the process of detaching itself. Once it separates, it will likely organize quickly. The system should become a tropical depression by the next day or two and attain at least tropical storm intensity. Though, there is a chance of it becoming a minimal hurricane, given the very favorable conditions ahead and its small size. I give 92E a 70% chance of developing into a tropical cyclone by the next 48 hours. 92E should continue to move west-northwestward and later northwestward. Then by Tuesday or Wednesday, the system should begin to move northward and make landfall on the Mexican coast near Puerto Angel around Thursday as depicted by the models. The system would bring strong winds and heavy rain, leading to life-threatening floods and mudslides, to that area. Interests along that area should monitor the progress of the low.

Figure 2. Water vapor imagery of Invest 92E. Image credit: Mauna Kea Weather Center (MKWC).

Potential development over northwestern Caribbean on early June
The GFS ensembles and other models have been consistent in showing the lowering pressures across much of the western Atlantic in the first few days of June. The upward Madden Julian Oscillation (MJO) pulse is currently in the eastern Pacific and is beginning to move into the western Atlantic and would remain in that region until early June. The upward MJO pulse will help enhance convection across much of the western Atlantic. In addition, shear is forecast to decrease gradually across the Caribbean by early June, allowing any development to occur. Although it is too early to tell that we will have a tropical cyclone developing out of this, development is still not out of the question yet.


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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2. WunderAlertBot (Admin)
8:56 PM GMT on May 27, 2013
Civicane49 has created a new entry.
1. KoritheMan
10:32 AM GMT on May 27, 2013
Thanks. Very informative.
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