Basement-dwelling pseudo-otaku with a thrill for forecasting on the side.
By: KoritheMan , 6:56 AM GMT on August 11, 2014
Notice: All forecasts presented here are based upon my own knowledge of atmospheric dynamics. They are created using my knowledge of the various computer models, satellite interpretation, and other tools and parameters. These forecasts, while striving to be accurate, are not intended to supersede predictions by the National Hurricane Center. Always follow NWS protocol and forecasts.
Hurricane Julio continues heading across the open Pacific well away from land. As of the 0300Z CPHC advisory bulletin, the following information was posted on the hurricane:
Wind: 85 mph, with higher gusts
Location: 25.5°N 153.5°W
Movement: NW at 13 mph
Pressure: 984 mb
Category: 1 (Saffir-Simpson Hurricane Wind Scale)
Julio's cloud pattern continues to gradually deteriorate. There is still considerable deep convection occurring near the center, but it is neither organized nor persistent; indeed, pulsating storms are indications that the environment is not favorable. Satellite estimates are falling, and it is possible Julio could be weaker than the 3Z operational intensity estimate by this point. Recent microwave data still shows some indications of a remnant mid-level eye, but even this feature is steadily disintegrating.
Figure 1. Latest infrared satellite image of Hurricane Julio. Image credit: NOAA's Satellite Services Division (SSD).
Julio is forecast to steadily weaken throughout the forecast period. The cyclone is currently being impacted by southwesterly shear associated with a broad mid- to upper-level trough located a few hundred miles north of the hurricane, which has caused the outflow in the western quadrant to take on a southwest-to-northeast orientation in tandem with the upper-level shear vector. The GFS and ECMWF connote various levels of shear over the next several days, but in general they appear to want to relax the upper flow over Julio between the 36-72 hour period (which I don't show due to the limitations of the map I use to draw track forecasts, and consequently forecast points), presumably in response to overhead ridging in the wake of the aforementioned trough. After that time, shear is forecast to increase again ahead of another, much larger upper-level trough now over the Bering Sea. Also, sea surface temperatures should remain around 25C throughout the next five days as Julio climbs toward higher latitudes, making reintensification unlikely even if the shear decreases. Actually, the hurricane could very well weaken faster than I what have shown here during the first 12-24 hours of the forecast.
Julio appears to be following the forecast track, as the 500 mb synoptic pattern remains decidedly straightforward. As mentioned previously, water vapor imagery projects an eastward-moving shortwave trough to the north of the hurricane. The global models show a low- to mid-level ridge temporarily replacing the trough in about 24 hours, so a more northwestward motion is expected at that time. While I've not indicated a forecast point beyond 48 hours here, there is some major disagreement amongst the models as to whether Julio will continue generally westward under a presumably deeper ridge, or if it will continue to move northwest before the ridge breaks again with the arrival of the second trough, which would coincide with an abrupt northward and northeastward acceleration into the mid-latitude westerlies. The ECMWF, CMC, and UKMET are to the left, while the GFS, GFDL, and HWRF are to the right. Based on current trends, I prefer the latter camp. This is also close to the latest CPHC prediction.
Initial 08/12 0300Z 25.5°N 153.5°W 75 kt 85 mph
12 hour 08/12 1200Z 26.4°N 154.1°W 70 kt 80 mph
24 hour 08/13 0000Z 27.2°N 155.1°W 65 kt 75 mph
36 hour 08/13 1200Z 28.1°N 156.4°W 60 kt 70 mph
48 hour 08/14 0000Z 28.9°N 157.6°W 55 kt 65 mph
Figure 2. My forecast track for Julio.
A weak area of disturbed weather located a couple hundred miles south of the coast of southern Mexico remains disorganized, with no deep convection near the center. Water vapor imagery shows strong upper-level winds over the system in response to a downstream ridge, but the GFS and ECMWF show this flow relaxing over the next few days, which should allow for some gradual development. In fact, it actually appears as though the shear may not increase as much previously thought, and shortwave infrared satellite pictures compliment the latest UW-CIMSS vorticity analyses by showing increasing low- to mid-tropospheric vorticity associated with the cloud center.
Figure 3. Latest infrared satellite image of Invest 99E. Image credit: NOAA's Satellite Services Division (SSD).
This disturbance is likely to move westward or west-northwestward over the next several days, and will likely not threaten land. It is likely to become a tropical depression sometime this week.
Probability of development in 48 hours: 20%
Probability of development in 120 hours: 70%
A tropical wave over the eastern Atlantic ("94L") is located just south of the Cape Verde Islands. Satellite images show that the system has recently lost all of its deep convection, likely due to 25-30 kt of easterly shear associated with a deep-layer ridge, and perhaps a bit of dry air. Water vapor imagery still shows that much of the MDR remains littered with dry air, with the latest UW-CIMSS Total Precipitable Water (TPW) animations showing the subsident portion of the Bermuda/Azores ridge slinging this dry air in the general direction of 94L rather nicely.
Figure 4. Latest infrared satellite image of Invest 94L. Image credit: NOAA's Satellite Services Division (SSD).
Upper-level winds may improve a little as the system heads westward and eventually west-northwestward, but are likely to remain generally unfavorable as the system heads either into or just north of the Caribbean. Although a little early to speculate on what is most likely going to be another innocuous tropical wave in a shear-ridden Atlantic, it should be noted that both the GFS and ECMWF show the developing mid- to upper-level trough over the eastern United States departing a little faster than they have been, with the trough likely to be replaced by ridging in about six or seven days. So assuming 94L hasn't gained enough latitude to where recurvature is inevitable, it is not out of the question that it could begin heading more westward by this time next week.
Probability of development in 48 hours: 0%
Probability of development in 120 hours: 30%
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.
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