Around 13 UTC September 13, 2015 (midnight local time) Category 5 Cyclone Pam made its nearest approach to Port Vila. The community was warned well ahead of impact, and it appears that many on the island heeded those warnings. While the damage in the city was severe to catastrophic, the infrastructure prevented things from being much worse. This is evident in several pictures we’ve seen, and the fact that limited communications have been restored with the city immediately after Pam’s departure.
As bad as the damage reports are coming out of Port Vila, we have reason to believe the other islands may have seen far worse destruction. The minimum recorded pressure in Port Vila reached about 942 hPa indicating that eye (estimated pressure around 900 hPa) passed just to the east. Port Vila likely missed the most destructive winds located within the far inner eyewall as the “weaker” western side (See below) impacted the city.
Thus far damage reports coming from other island have been non-existent. Communications were entirely cut off. Several of these other islands, especially Erromango and Tanna, likely experienced more severe cyclone winds and damage. The storm passed just to the west putting them in the more destructive eastern quadrant. Also, infrastructure is minute compared to Port Vila with little in the way of protection from a storm as powerful as Pam. Hopefully we’ll hear more from other regions in Vanuatu later today. Check this page for continued updates:
http://www.28storms.com/cyclone A tropical disturbance northeast of the Solomon Islands has the potential to develop into a Severe Tropical Cyclone in the coming days. Stay tuned to the cyclones page for more video updates.
It has quietly been a somewhat active month for tornadoes between eastern Texas and southern Georgia. There have been five separate tornado “days”, with none of which gathering more attention than the December 23rd event that resulted in four fatalities in Columbia, Mississippi.
Friday and Saturday (Jan 2nd/3rd) will feature heavy rain, severe storms, and potentially more in the way of isolated tornadoes across the Deep South. This morning’s mid to upper level water vapor imagery captured a longwave trough with embedded shortwaves dipping into California and Nevada. As this trough slowly advances eastward over the next 2-3 days, it will provide enough upper level divergence and atmospheric lift to spawn low pressure at the surface. The first and fairly weak surface low will develop near the upper Texas and western Louisiana coasts on Friday, before a more dominant surface cyclone takes shape near Memphis by Saturday.
Despite the presence of low pressure, many more ingredients will have to come together in order for severe storms to develop. Most importantly, a warm, moist, tropical, and unstable airmass needs to be advected northward out of the Gulf of Mexico. With Friday’s coastal low being so weak and far south, it will be difficult for the “warm sector” to make it beyond shelf waters during the day. Below is a very coarse depiction of the position of the low and accompanying warm front based on GFS model guidance valid 6PM Friday.
Green colors on this graphic represent areas with Convective Available Potential Energy (CAPE) of 750j/kg or higher. Obviously, the severe threat will be limited to extreme southern coastal parishes of Louisiana and coastal counties of Mississippi until the warm front advances farther north. The onset of rainfall and isolated, non-severe thunderstorms will occur much sooner, however, as elevated instability will already be present along and even north of the frontal boundary. The Storm Prediction Center (SPC)is keenly aware of the setup, and their outlook for Friday includes a marginal risk in the same area highlighted above.
Their outlook is valid through Friday night, which is the reason why their marginal risk area extends as far north as Baton Rouge and almost McComb. The warm front will lift north throughout the night. By 6AM Saturday, the lowest surface pressures will be located over eastern Arkansas, which should allow the warm sector to make it well inland, and into south-central Mississippi by the early afternoon hours.
SPC has opted to not highlight any areas for severe weather on Saturday just yet. Their reasoning is due to uncertainty given large model differences, and the conditional nature of Saturday’s threat in general. Widespread severe storms may not materialize at all, for example, if the warm sector is not as potent as indicated by some guidance. With that said, there does appear to be enough data supportive of a few weak, isolated tornadoes and storms capable of damaging wind gusts. The two graphics below represent CAPE in excess of 750 j/kg across southern Mississippi and southwest Alabama, with moderate low level wind shear also present along the northern third of the unstable warm sector midday Saturday. Where these two parameters overlap is where the best bet for isolated tornadoes would be.
One negating factor is that by this time, the amount the change in wind direction with height will be lessening. With a trailing cold front quickly approaching, winds near the surface will be in the process of veering from southeast to southwest, which lines up better with the mid-level southwesterly flow already present with the mid-level trough swinging through the South. Therefore, dominant storm mode will likely evolve into a squall line, with the main threat being damaging winds with a non-zero risk of a few isolated weak, rain-wrapped, and embedded tornadoes. Needless to say, there are still a lot of question marks, but also a lot of reasons why you should be weather-ready along the Gulf Coast late Friday into Saturday.
One risk that also should not be overlooked is the threat of heavy rain. The Deep South has already encountered a few heavy rain events in recent weeks. With the ground already saturated, it wouldn’t take much heavy rain to cause a few pockets of flash flooding. Below is the five day accumulated rainfall forecast for the area.