Daily Archives: Tuesday, July 26th, 2011
If you’ve been following my tweets over the last day or so, you would know that Invest 90L was reactivated yesterday after it temporarily fell apart. Conditions are much improved tonight, and I believe this will be Don within 48 hours. The National Hurricane Center gave 90L a 40% chance of development at 8pm, which I whole heartedly agree with. The early models from the NHC are out now, and I will talk about those and my forecast track and intensity below.
Invest 90L is still a tropical wave, and is clearly not closed off as of the 10pm hour. All winds are out of the SE, E, or NE near the wave with absolutely no evidence of a westerly wind. The winds in the Caribbean are generally out of the east, so there must be cyclonic turning in the atmosphere in order for westerly winds to occur. The tropical wave fired off amplified storms in Cuba and Florida today, which shows me that the moisture envelope is well in tact. The lower and upper level air flow is building, in other words 90L is breathing enough to sustain itself, and is breathing with less effort. This is a sign that the cyclone is organizing. Below I look at each of the conditions that affect cyclones:
- Convergence: Seems to be coming together quite nicely and is growing in the low levels. Condition: good
- Divergence: Divergence aloft is also building. Condition: good.
- Shear: I see very little evidence of shear taking thunderstorms away from the core. I do see a flatness on the western side of the storm that may be shear induced. This should go away. Condition: fair.
- Vorticity: The spin in the atmosphere is ever building, not only at the surface but also in the middle layers. Condition: great!
- Humidity: What dry air? Condition: great!
- Water Temperature: Hot as always in the Caribbean. Condition: great!
- Weak Tropical Storm by mid to late-afternoon tomorrow
- Maximum intensity of 60-70 mph on Thursday or Friday near landfall
- There is a chance of a stronger than anticipated intensification if every variable becomes very favorable, which I believe is possible. I think there is a 20% chance of this happening.