Gone with the wind shear; TD #Two-E a threat to Mexico; Watching the Atlantic
In a quick manner, the first tropical storm of the 2012 Atlantic hurricane season, Alberto, formed during the afternoon hours of Saturday from a warm-core low pressure area that formed over the Gulf Stream underneath an upper-level trough split. Just as quick, Alberto is on a weakening trend this afternoon and likely not a tropical storm any longer after attaining a peak intensity of 60 mph with a barometric pressure of 995 millibars. This is due to strong wind shear out of the west-southwest. No further strengthening is forecast from Alberto despite the fact that Sea Surface Temperatures lie near 27 °C (81 °F), above the values needed to sustain a tropical storm. The system has begun an eastward movement, and should turn northeast as a trough deepens to the cyclone's west. Alberto is such a compact storm and remains far enough offshore that it should not affect any land areas.
INIT 22/0000Z 35 KT 40 MPH
12H 22/1200Z 30 KT 35 MPH
24H 23/0000Z 30 KT 35 MPH
36H 23/1200Z 25 KT 30 MPH...POST-TROP/EXTRATROP
48H 24/0000Z 25 KT 30 MPH...DISSIPATED
Figure 1. Afternoon visible satellite imagery of a weakening Tropical Storm Alberto.
Tropical Depression Two-E destined to become a Mexico threat
The second tropical depression of the 2012 Pacific hurricane season, Two-E, is likely to become a significant threat to Mexico over the coming days. The system has taken some time to organize today due to its large size and connections to the monsoon trough, but recent visible satellite loops reveal a sharp increase in organization. The latest National Hurricane Center advisory centered Tropical Depression Two-E at 9.6 °N 101.0 °W with maximum sustained winds of 30 knots (35 mph) and a minimum barometric pressure of 1005 millibars. The depression is currently on a west-northwest motion but is expected to turn northwest, north, and northeast over the coming days as a strong trough passes over the US Central Plains and draws Two-E northward.
An objective analysis from the Cooperative Institute for Meteorological Satellite Studies (CIMSS) reveals Tropical Depression Two-E is in a very favorable environment for further intensification characterized by Relative Humidity values above 70% and wind shear between 5-10 knots. The atmosphere should continue being favorable for strengthening as the week progresses, and Tropical Depression Two-E is poised to become "Tropical Storm Bud" later tonight and "Hurricane Bud" by Wednesday morning. Some of the global models indicate that the system could undergo a period of rapid intensification, and in fact, the latest SHIPS model forecast gave TD #Two-E a 56% chance of undergoing a 25 kt rapid intensification over the next four days. As the trough of low pressure pulls the cyclone northward, an increase in wind shear will likely cause weakening before landfall on the Mexican coastline late Thursday night or Friday. Once inland, Two-E should weaken quickly over the highly mountainous terrain.
INIT 22/0000Z 30 KT 35 MPH
12H 22/1200Z 45 KT 45 MPH
24H 23/0000Z 60 KT 60 MPH
36H 23/1200Z 70 KT 75 MPH
48H 24/0000Z 75 KT 85 MPH
72H 25/0000Z 95 KT 105 MPH
96H 26/0000Z 70 KT 80 MPH
120H 27/0000Z 60 KT 70 MPH...INLAND
Figure 2. Afternoon visible satellite imagery of a strengthening Tropical Depression Two-E.
Watching the Atlantic
An area of disturbed weather associated with a weak low pressure area in the Gulf of Honduras is producing heavy shower and thunderstorm activity across surrounding areas of the Caribbean Sea and southern Gulf of Mexico. Satellite loop analysis reveals potential broad cyclonic turning in the lower levels of the atmosphere, but immediate development is not expected as wind shear lies between 20-40 knots. Despite this, a few of the global models attempt to spin this up into a decent low pressure area as the week progresses. This is likely due to a brief letup of wind shear across the region, and organization of this low pressure is certainly possible. However, a combination of land interaction and increased wind shear afterwards means that anything organized will quickly become disrupted. I give this disturbance a Low, ~0% chance, of becoming a tropical cyclone in the next 48 hours.
The Western Caribbean will need to be watched over the next 10 days as a strong high pressure builds across the Eastern USA, causing heights there to rise and heights across the Gulf and Caribbean to lower. The GFS and ECMWF show the potential for mischief to occur as wind shear lowers across the region, but not all models show this solution and any development would be monsoonal, or slow, in nature.
The final area that will need to be watched as we head into the weekend is off the East Coast of the USA. A few of the global models show the potential for tropical or subtropical development off the coastline as a strong trough digs into the Western USA, causing a southwest to northeast orientation of the high pressure across the East USA. This would allow for an upper level disturbance to get "stuck" off the coast of North Carolina and South Carolina over the Gulf Stream, in a very similar manner to the synoptic pattern that spawned Tropical Storm Alberto.
Figure 3. Afternoon black/white infrared imagery of the West Atlantic.