Hawaii braces for Felicia; 99L near the Cape Verdes Islands may develop
A strong tropical wave (99L) is just south of the Cape Verdes Islands, 800 miles off the coast of Africa. This morning's QuikSCAT pass showed a nearly closed surface circulation, stretched out along one axis. The satellite saw winds of up to 45 mph in a band of heavy thunderstorms well south of the Cape Verdes Islands. The islands have seen winds of only 10 - 15 mph and some occasional rain showers thus far from the disturbance. Heavy thunderstorm activity associated with 99L died down this morning, but appears to be making a comeback late this morning. Wind shear is moderate, about 10 knots, and sea surface temperatures are moderately warm, about 27 - 28°C. There is a large area of dry air to 99L's north that is interfering with the storm's organization, though.

Figure 1. Current satellite image of disturbance 99L.
Wind shear is expected to be moderate, 5 - 15 knots, through Wednesday. SSTs will remain relatively constant at 27°C, but the dry, stable air of the Saharan AIr Layer (SAL) to 99L's north will be problem for it. NHC has given 99L a moderate (30 - 50% chance) of developing into a tropical depression by Wednesday morning, which is a reasonable forecast. Most of the models show some weak development, but none of them predict 99L will become a hurricane. It is too early to say if 99L will recurve north of the Lesser Antilles Islands or not, since it will be at least 5 days before the storm makes it that far. It is unusual, though, for storms forming this far north to make it all the way across the Atlantic to hit the Lesser Antilles Islands.
The GFS and ECMWF models are predicting the possible development of a new tropical wave coming off the coast of Africa late this week.
Felicia continues to weaken, but is a flash flooding threat to Hawaii
Tropical Storm Felicia has weakened steadily over the past 24 hours, thanks to cool sea surface temperatures and increasing shear. Recent satellite loops show that strong upper-level winds from the west have pushed the storm's heavy thunderstorm activity to the northeast side of the center, exposing the surface center as a swirl of low clouds. Felicia's relatively meager heavy thunderstorm activity is steadily moving away from the center of the storm.

Figure 2. History of hurricane activity over Hawaii since 1950. Hawaii islands have been hit by only 9 tropical cyclones of tropical depression or greater strength, with 4 others passing withing 75 miles of an island. Image credit: NOAA Coastal Services Center.
Sea surface temperatures (SSTs) under Felicia are 25°C, well below the 26°C threshold typically needed to sustain a hurricane. SSTs will slowly increase to 26°C by Tuesday. Wind shear has increased to a high 30 knots, and is expected to increase further to 40 knots by Tuesday. The high shear combined with the cool SSTs should continue to weaken Felicia today. I give a 30% chance that the shear will completely rip away Felicia's heavy thunderstorm activity by the time the storm reaches Hawaii, leaving only a swirl of low-level clouds that will not cause significant flooding problems. The wind speed probabilities forecast shows about a 25% chance Felicia will still be a weak tropical storm at 3 am Hawaiian time Tuesday morning, and a 15% chance the storm will have dissipated. If Felicia does hold together that long, it would be only the tenth tropical cyclone of tropical depression or higher strength to affect the islands since 1950 (Figure 2). Large swells from Felicia are already affecting the Big Island, and a high surf warning has been posted for east-facing shores of the Big Island and other Hawaiian islands. Felicia or its remnants may bring heavy rain, flash flooding, and mud slides to the islands beginning this afternoon, and a Flash Flood Watch has been posted for most of the islands.
Links to follow:
Long range radar from the Big Island
Wundermap for Hawaii
I'll have an update Tuesday morning.
Reader Comments
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I was just looking at that. Almost all state met offices are talking about it.
WOW... That's a shame...
ya like you in that dress..
Increased rain chances.
He doesn't know how to type or proofread, all his posts are like that.
What do you know, we got a little yeller fella out there now. Maybe at least a little SE rainmaker if nothing else.
Maybe not, but I can proofread my post before I post.
Link
And so the train starts...
Is now....
Still shows 99L developing. I still think it has a chance but its obviously going to take some time.
See what you started IKE. Its all your fault for posting models.
Think that's the wave near 45-47W it shows on the first frame. Takes it into the GOM as a wave.
I can't help how he reacts. Not my fault.
99L might just be like Hurricane Irene in 2005. Kept at TS strength, then weaking it to TD strength then back to TS strength until it got near Bermuda, then got a bit stronger, became a hurricane and headed out to sea. The EURO has sort of a similiar track from Irene as well with 99L.
I still think it has a chance especially if the Euro is latching on to it. May bet he most aggressive run yet with the system. It will probably take 24-48hrs
Not showing much except, and unfortunately, an all to familiar track for 90L? up the spine of the Caribbean Islands. Not much left of it after that. I've thought from the beginning and still do think that 99L will re-curve forming just ahead of the changes.
Might be.. it's hard to pinpoint when the model starts at 75 hours lol
I think ANA will turn north before 55w.
Amen. This is day 71 with 0-0-0. The only way I'm ever saying any system is named is when the NHC does ONLY.
PS...that goes for invests too.
not showing much? it develops 3 systems
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