Tropical weather analysis - June 20, 2012
Tropical Storm Chris strengthened a little today. As of the most recent advisory from the National Hurricane Center, the following was posted:
Wind: 60 mph, with higher gusts
Location: 38.5°N 49.0°W
Movement: E at 21 mph
Pressure: 997 mb
Category: Tropical storm (Saffir-Simpson Hurricane Scale)
Well, what do we have here? Is Chris sporting an eye? I think he is. Over the last several hours, and shortly after the release of the current advisory, the cyclone began to exhibit a large eye-like feature in the central convection. This feature has since persisted, and the thunderstorm activity is wrapping cyclonically around this feature in all directions. I daresay Chris may be trying to make a shot at hurricane strength.
Figure 1. Latest infrared satellite image of Tropical Storm Chris. Image credit: NOAA.
Chris is at the base of an upper low. Southwesterly mid- to upper-level flow on the east side of this low is helping to promote upper-level diffluence, and thus convection. This may be why the cyclone has been able to strengthen over SSTs of about 22C. However, this low is forecast to amplify and eventually move away from Chris. As this happens, there are two possibilities: the first is that Chris remains the dominant system; the second is that the cyclone becomes absorbed by the developing baroclinic system to its west. Lacking any obvious reason why I shouldn't, I'll continue the trend in the previous forecast of the cyclone merging with said extratropical cyclone in a few days.
While Chris definitely looks healthy, and the feature seen on satellite images probably is an eye, I am doubtful that the cyclone will be able to adequately transport the hurricane force winds -- which likely exist aloft -- down to the surface. I will forecast a little more strengthening, but not to hurricane strength.
The track forecast remains straightforward. Chris is moving around the eastern periphery of the aforementioned upper low, and the global models suggest that it will continue to move in a broad cyclonic fashion around this low.
5-day intensity forecast
INITIAL 0000Z 06/20 50 KT 60 MPH
12 hour 1200Z 06/20 55 KT 65 MPH
24 hour 0000Z 06/21 50 KT 60 MPH...EXTRATROPICAL
36 hour 1200Z 06/21 45 KT 50 MPH...EXTRATROPICAL
48 hour 0000Z 06/22 45 KT 50 MPH...EXTRATROPICAL
72 hour 0000Z 06/23...ABSORBED BY DEVELOPING BAROCLINIC LOW
5-day track forecast
Figure 2. My 5-day forecast track for Chris.
A large area of disturbed weather continues over the northwestern Caribbean Sea in association with a sharp surface trough. The National Hurricane Center hasn't officially designated this system an invest yet, because that requires a definitive low pressure center, of which there currently is none.
Satellite and CIMSS real-time vorticity data suggest that there are two distinct circulation centers within the overall cyclonic gyre. The first of these is a convectionless swirl moving over the eastern Gulf of Mexico west of the Florida Keys; the second is located inland over the northern Yucatan Peninsula. While both of these lows are still primarily mid-level, a couple of surface observations from the Yucatan Peninsula suggest that the secondary vortmax may become the dominant system; Merida recently reported northeasterly winds, and Campeche, located about 100 miles to the southwest, reported northerly winds, and there were even a few reports of westerly winds in the area. Both these locations lie along the western coast of the peninsula, and their respective locales and finely spaced so that such observations bear mentioning. However, I can't ignore the convection afflicting the western Caribbean from the Yucatan Peninsula to the Isle of Youth, which, although will likely due once the diffluent flow aloft over the Gulf of Mexico lifts northward, may try to combine with the Yucatan center, and form a center closer to the north or northeast coast, rather than in the Bay of Campeche. I am not confident enough to say anything else right now.
The models continue to indicate a Florida landfall, but as I said yesterday, until we get a definitive center established, this track isn't set in stone. It would also be climatologically favored for a more gentle recurvature, not the sharp one the models are portraying. At this time, interests along the entire Gulf Coast should be attentive to the progress of this system, which the models develop into a tropical cyclone over the central Gulf of Mexico in a few days, underneath more favorable upper-level winds.
Regardless of development, heavy rains will continue affecting the western Caribbean and neighboring nations, including Mexico's Yucatan Peninsula, western and central Cuba, and possibly south Florida and the Florida Keys at times.
Probability of development within 48 hours: 40%