Tropical weather analysis - July 13, 2012
Emilia has weakened to a tropical storm. The latest NHC coordinates were as follows:
Wind: 50 mph, with higher gusts
Location: 15.5°N 127.2°W
Movement: W at 15 mph
Pressure: 996 mb
Category: Tropical storm
The cyclone continues to generate convection, and has actually gained a little bit of organization in recent satellite frames. However, arc clouds can be seen emanating from the eastern quadrant, meaning that Emilia is struggling with dry air. The deepest convection is limited to the southern semicircle. Not surprising considering that portion of the circulation is over slightly warmer water temperatures.
Figure 1. Latest infrared satellite image of Tropical Storm Emilia. Image credit: NOAA
Emilia is expected to continue weakening as it moves westward south of a strong subtropical high. Big brother Daniel seemed to fare better at this longitude than Emilia did. Perhaps it is because his little sister is passing over his cool wake. However, I have not analyzed the areal sea surface temperatures very much, so this is admittedly speculation on my part. In any event, the cyclone is forecast to dissipate by Sunday, quicker than in my previous evaluation. Emilia is expected to pass far enough south of the Big Island next week as to not deliver any appreciable rainfall. However, the vigorous cyclonic circulation associated with then post-tropical Emilia will undoubtedly disrupt the trade wind flow that normally dominates the region.
There isn't much new to say about the forecast track, either. The cyclone is expected to continue moving west until it crosses 140W longitude, at which point the models suggest a turn to the southwest could begin.
5-day intensity forecast
INITIAL 07/13 2100Z 45 KT 50 MPH
12 hour 07/14 0600Z 40 KT 45 MPH
24 hour 07/14 1800Z 35 KT 40 MPH
36 hour 07/15 0600Z 30 KT 35 MPH...POST-TROP/REMNANT LOW
48 hour 07/15 1800Z 25 KT 30 MPH...POST-TROP/REMNANT LOW
72 hour 07/16 1800Z 20 KT 25 MPH...POST-TROP/REMNANT LOW
96 hour 07/17 1800Z 20 KT 25 MPH...POST-TROP/REMNANT LOW
120 hour 07/18 1800Z 20 KT 25 MPH...POST-TROP/REMNANT LOW
5-day track forecast
Figure 2. My 5-day forecast track for Emilia.
Fabio strengthened to the fifth hurricane of the Eastern Pacific season earlier today, over a month ahead for the climatological date of August 26. The most recent NHC advisory had this to say:
Wind: 80 mph, with higher gusts
Location: 15.6°N 111.4°W
Movement: WNW at 10 mph
Pressure: 986 mb
Category: 1 (Saffir-Simpson Hurricane Scale)
The cloud pattern is gradually becoming better organized, and Fabio still has a chance to intensify a little more. However, the large-scale environment does not appear conducive to rapid intensification. A ragged eye feature is evident in satellite pictures, with vigorous convection encompassing it to the east.
Figure 3. Latest infrared satellite image of Hurricane Fabio. Image credit: NOAA
Fabio is still experiencing northeasterly shear, which appears to be defying me and sticking around longer than I had anticipated. But as alluded to yesterday, this shear does not appear strong enough to penetrate the core and cause weakening. I guess I owe the SHIPS credit after all, at least for predicting the shear to stick around.
Interestingly, there seems to be a flagrant dichotomy between the SHIPS SST output, and that provided by AOML. As of 0z, the former insists that Fabio is sitting underneath water temperatures of 27.6C, while the latter suggests that the hurricane is about to traverse the 26C isotherm. Lacking any real-time observations in the vicinity of the hurricane to confirm or deny either analysis, I have little choice but to judge by the current cloud pattern. With little apparent reason, convection is weakening in the western semicircle, which probably means that the SHIPS analysis of areal water temperatures is a little high. However, I sincerely doubt any portion of Fabio is over sub-26C water at the moment, and with little change in the environment since yesterday, I will continue to call for intensification for the next 12-24 hours. Thereafter, the hurricane should begin to weaken even though the shear is forecast to decrease. SSTs drop off sharply after about 48 hours, so rapid weakening is expected subsequent to that point. Fabio is forecast to dissipate by the end of the forecast period, although given the cold waters it could occur sooner. Although not explicitly shown, there is still a chance Fabio could briefly become a Category 2 hurricane prior to encountering the cooler waters.
As far as track, the models have generally come into better agreement, with Fabio expected to gradually turn north. A northeastward turn is possible at the end of the forecast period, although this is not explicitly indicated at this time. Fabio is likely to enhance moisture across portions of southern California and the desert southwest next week as its mid-level remnants move northward.
5-day intensity forecast
INITIAL 07/13 2100Z 70 KT 80 MPH
12 hour 07/14 0600Z 80 KT 90 MPH
24 hour 07/14 1800Z 80 KT 90 MPH
36 hour 07/15 0600Z 70 KT 80 MPH
48 hour 07/15 1800Z 60 KT 70 MPH
72 hour 07/16 1800Z 45 KT 50 MPH
96 hour 07/17 1800Z 30 KT 35 MPH
120 hour 07/18 1800Z 25 KT 30 MPH...POST-TROP/REMNANT LOW
5-day track forecast
Figure 4. My 5-day forecast track for Fabio.