16-yr-old weather aficionado, with primary focus on tropical cyclones. High school and college student, working towards the National Hurricane Center.
By: TropicalAnalystwx13 , 3:37 AM GMT on June 29, 2013
It's only been three days since my last blog, but since that time we've the East Pacific has birth another disturbance well on its way to becoming a tropical depression. Dubbed Invest 96E, the National Hurricane Center is currently giving the disturbance an 80% chance of tropical cyclone formation within 48 hours. Satellite loops reveal the system is well organized, with a defined and presumably closed low-level circulation and prominent outflow pattern. Shower and thunderstorm activity has been on the decrease over the past few hours, but this may just be a result of diurnal minimum - when the instability between the land and ocean is at its lowest. The latest satellite intensity estimates from SAB were T1.5/25 knots; in order for advisories to be initiated on a tropical cyclone, a value of T2.0/30 knots is typically needed. It is likely that 96E will attain tropical depression status tomorrow morning, and I give it a Near 100% chance of becoming a tropical cyclone over the next 48 hours accordingly.
Figure 1. Black/white infrared satellite imagery of Invest 96E.
Forecast for 96E
Invest 96E is in a very favorable environment for intensification. Maps from the University of Wisconsin-Madison indicate the presence of anticyclonic flow in the upper 200 millibars of the atmosphere. This is providing low wind shear for the tropical disturbance, and these favorable values of less than 10 knots are forecast by the SHIPS to remain throughout the entire period. Sea surface temperatures are currently around 29C, and may increase ever so slightly before becoming unfavorable for further development at the end of the forecast period. Relative humidity values between 700-500mb were analyzed in the lower 80s (%) but are expected to perhaps be the most detrimental to development; values should drop into the upper 60s to lower 70s after 48 hours. Heat content is currently in the 20s (kJ/cm^2) but is forecast to increase to the 50s by 48 hours. Unlike Cosme, Invest 96E is a very compact system; this greatly increases its chances of rapid intensification under favorable atmospheric conditions. In fact, the SHIPS is giving the disturbance a 6/10 of 25-kt rapid intensification over the next 2 days. All things considered, I expect 96E to become a tropical depression in the morning and a tropical storm tomorrow afternoon. Steady intensification should occur thereafter, at least until a well-defined inner core is built. I expect Invest 96E to attain hurricane intensity in 48 hours, and peak as a low-end Category 2 in 72 hours. Decreasing sea surface temperatures will likely slowly weaken the storm at the end of the period.
Models remain in impressive agreement regarding the forecast track of Invest 96E. Though the storm has been tracking generally west, an abrupt shift to north or north-northeast is expected over the next 24 hours as a result of troughiness over inland Mexico and the Gulf of Mexico. This motion is expected to continue for roughly 48 hours; after this time, an expanding region of high pressure is expected to replace the troughing over Mexico and force the storm northwest and likely west-northwest towards the end of the period. It should be stated that the current model guidance shows the center of what should be a potent hurricane at the time passing less than 200 miles from the coastline of Mexico. Any small change in the pattern north of the storm may lead to huge changes in the track. Regardless of a landfall, outer bands are likely to impact the coastline from Mazatlán to Acapulco. These bands are likely to deliver gusty winds, possibly in excess of tropical storm-force, and torrential rainfall capable of producing mudslides, landslides, and street flooding. Wave heights along the coastline are expected to be abnormally high, and rip currents will become a great concern for beach-goers. Tropical cyclone advisories will likely be needed for a stretch of the coastline of Mexico accordingly.
...FORECAST POSITIONS/MAX WINDS...
INIT 29/0300Z 10.8N 104.6W 25 KT 30 MPH
12H 29/1200Z 11.7N 104.2W 30 KT 35 MPH
24H 30/0000Z 13.1N 103.9W 40 KT 45 MPH
36H 30/1200Z 14.6N 103.9W 50 KT 60 MPH
48H 01/0000Z 16.2N 104.4W 65 KT 75 MPH
72H 02/0000Z 18.2N 106.2W 85 KT 100 MPH
96H 03/0000Z 19.1N 108.3W 80 KT 90 MPH
120H 04/0000Z 19.0N 109.9W 75 KT 85 MPH
Tropical wave near Lesser Antilles
An impressive tropical wave for this time of the year - something we've seen countless times so far this season - is currently located near the Lesser Antilles. Satellite loops reveal the tropical wave is disorganized, with meager convection located mainly in the eastern semicircle of the wave axis. However, surface observations and data from global model guidance wind maps indicate that the wave actually has a well-defined and closed low-level circulation. The National Hurricane Center is currently giving this wave a Near 0% chance of development within 48 hours; I agree with these chances. While the wave is abnormal for this time of the year, and likely a sign of things to come next month and on, high wind shear from the subtropical jet stream is expected to deter any tropical development, at least until the southwest or west Caribbean. Once it reaches this region, lower wind shear and the influence of the upward pulse of the Madden-Julian Oscillation and a convectively-coupled Kelvin Wave may spark development, as indicated by the GFS ensembles. Regardless of any development, this wave is likely to bring heavy rainfall and gusty winds to the islands occupying the southern Caribbean Sea.
Figure 2. Black/white infrared satellite imagery of the tropical wave located east of the Lesser Antilles.
Cosme of little concern
I apologize for the lack of blogs on Cosme over the past few days. Since my previous one, Cosme peaked in intensity as a strong Category 1 hurricane, and ultimately died a typical death across the East Pacific; a result of cooler sea surface temperatures and stable air aloft. The circulation remains very well-defined on satellite imagery, and is undoubtedly closed. However, due to the factors that killed it, the remnants of Cosme are not expected to be a candidate for redevelopment. The low-level circulation is likely to continue tracking due west and may impact the Hawaiian islands in a little under a week. Due to the orography of the islands, locally torrential rainfall may result. Higher waves and an increased threat of rip currents may accompany the system as well; overall, there is little need for concern.
I'll have a new blog on what should be the next East Pacific tropical depression tomorrow,
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