9:00pm Ana update Anas current condition: estimated intensity from infrared satellite imagery is 995.6mb 57.0kt. Thats still a ways from hurricane status, which begins at 64kts. So shes not as strong as Iselle yet. From the intensity estimate graph, it is clear that she is in a strengthening phase. Factors contributing to strengthening tonight: diurnal maximum, sufficiently warm SSTs, relaxing shear, good access to moisture source from the ITCZ. Okay lets take them one by one. Diurnal maximum, cooling of the upper atmosphere at night helps destabilize the atmosphere. Sufficiently warm SSTs, 26C is the cutoff and Ana is over 27.5C water. Warm enough, but not really warm. Relaxing shear, SHIPS model continues to show shear under 5kts for the rest of the night. When shear gets high, 10-15kts and above, it tends to strip convection away from the center of circulation and thats make for a weaker storm. Good access to moisture from the ITCZ, the river of moist air to the south of Ana that is feeding her from that side is call the Intertropical Convergence Zone. It is an area of moist and rising air that circles the planet near the equator. The feed is robust and thats feeding lots of energy into Ana, but thats pretty much her only source of moist air. On the other 3 sides, west, north, and east, shes looking at much drier air. Factors limiting strengthening. What relaxing shear? No distinct eye. Limited time frame. Poor history of intensification. Lets start with what relaxing shear? When you look at Anas weak side in the satellite image below, it looks completely different from the rest of her. Why the heck does the SHIPS model keep calling for shear to be gone? Im not believing it until I see it with my own eyes. I think its still there and getting in the way. No distinct eye, not by a long shot. As a matter of fact the convection is lopsided toward the east end. Limited time frame, she supposed to be passing by in around 24 hours. Times a running out. Poor history, she has never actually gotten her self organized. Maybe shes not going to. As far as her path goes, she has strengthened some, and shes a tiny bit on the north side of the forecast points in the last satellite image. But, thats only news because shes been south of those points for so long. Shes well within the bounds of error. The high to the north of Ana is a little stronger than originally thought, and that will push on her from that direction. The flow in the upper atmosphere is pushing from the south. If she were a much deeper system with pressure of 970mb instead of 995mb, maybe shed feel that and head towards the north. So, well have to keep an eye on that. Not likely, but always possible. Other than that, the CPHC forecast points look spot on. Of course, those folks are awesome! Wind is a little tricky, because there could be strong convective squalls that form on the periphery of her core circulation. They could have associated gusts that can cause damage and interrupt power. And theres going to be a real lot of rain. But we can handle that. Were the rain champions here! At Hawaiian Beaches were seeing 6-10 breakers at sundown. I expect Pohoiki to have 2-3 times overhead surf tomorrow. But itll probably be blown out. Surf at South Point my be closer to 3-4 times overhead. I dont know the storm surge potential at Kapoho, and I could find no information online. But the storm and the surf are both coming from the south and thats a bad direction for Kapoho, keep safe and get out is probably the best advice for anyone in low lying areas on the southeast coast. Ill get up in the middle of the night and check to see if anything crazy is going on, but Im expecting that shes well behaved and sticks to the forecast points the the CPHC has laid out for her. Morning update first thing, unless conditions warrant otherwise. Night all.
Posted on: Fri, 17 Oct 2014 07:18:18 +0000
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