Little change to Maria; Extratropical Storm Katia batters the U.K.

There's not much new to report this morning regarding Tropical Storm Maria. Maria continues to creep slowly to the northwest, and continues to struggle with moderate wind shear of 15 - 20 knots that is preventing the storm from organizing. Satellite loops reveal a shapeless mass of heavy thunderstorms that don't much resemble a tropical cyclone. Long-range radar out of Puerto Rico does show a few respectable low-level spiral bands, and these bands have brought heavy flooding rains to the island this morning. Radar-estimated rainfall amounts over eight inches have occurred over portions of southern Puerto Rico, and flash flood warnings are posted for the La Plata River.


Figure 1. Morning radar image of Tropical Storm Maria from the Puerto Rico radar.

The trough of low pressure that is bringing hostile wind shear to Maria is predicted to weaken slightly on Wednesday, which may allow the storm to grow to Category 1 hurricane strength. Intensification will be hampered by the fact that Maria will be passing over the cold water wake left by Hurricane Katia, though. NHC is giving Maria a 24% chance of reaching hurricane strength in their 5 am EDT wind probability forecast. On Thursday, Maria will be making its closest approach to Bermuda. Bermuda will see an 8-hour period of sustained winds in the 25 - 35 mph range, accompanied by heavy rain squalls, beginning near 2 am local time on Thursday. Most of the models show that Maria will brush or strike Newfoundland, Canada on Friday afternoon. Heavy rains will be a flooding threat to the west of where Maria passes, and tree damage and power failures from high winds of 45 - 55 mph will be a concern to the east of where the center goes.


Video 1. Video of what Extratropical Storm Katia's winds were like at Malin Head, Ireland, at 1:45 pm September 12, 2011. Wind gusts reached 75 mph on Malin Head during the storm.

Extratropical Storm Katia batters the U.K.
The extratropical version of Hurricane Katia roared over northern Scotland in the U.K. yesterday, bringing hurricane-force winds gusts and heavy rains to much of the British Isles. Glen Ogle, Scotland, at an elevation of 1500 feet (546 meters), received sustained winds of 60 mph, gusting to 86 mph, at 1900 local time. Cairngorm, in the Scottish Highlands at an elevation of 4085 feet, reported sustained winds of 67 mph at 6:50 pm local time. With the trees in full leaf, tree damage was much higher than a winter or springtime storm of similar ferocity would have caused. One person was killed by a falling tree, and heavy tree damage and numerous power failures were reported throughout Britain. Other gusts experienced in Britain included 76 mph at Edinburgh Blackford Hill, 75 mph at Capel Curig in Wales, 72 mph at Glasgow Bishopton, and 71 mph at Loftus, North Yorkshire.

Wunderground's weather historian, Christopher C. Burt, says that Cairngorm summit holds the U.K. record for highest wind gust, with 172 mph measured on March 20, 1986. The record wind gust at a low-level site is 141 mph at Kinnaird's Head Lighthouse, Scotland, on February 13, 1989. Damage on the Isle of Skye during this storm was such that wind speeds in excess of 150 mph were estimated.

Elsewhere in the tropics
Several of the models predict the development of a tropical depression or strong tropical disturbance 4 - 5 days from now off the coast of Africa. The NOGAPS and GFS models are predicting the Western Caribbean could see the development of a tropical depression 7 - 8 days from now, as moisture from the Eastern Pacific flows northeast into the Caribbean.

Jeff Masters