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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Sorry, didn't get the extra "S" out of dessert before the quote LOL.
Did someone say hurricane party? I fully plan on a big bash when the long overdue day of judgment comes to Savannah. I guess you could say partying is how we deal with grief and tragedy around here.
We'll be rolling on River Street when the big blow comes. :)
TWOAT will be out momentarily
There is absolutely no way.
We will be very lucky if somewhere isn't struck by a Cat 4 or worse. The ocean heat content will be very high by the time a system comes in this general direction and 4 days of a good upper level environment will have no trouble producing a major hurricane.
no argument , it might even be back to yellow, I'm just stating my opinion.
Nope. It doesn't even deserve an orange.
Bet the NHC doesn't give an encouraging update on it.
More organize that for sure has a close Low Red at 2AM TWO since NHC is very conservative and they want to see the convection firing around that Low.
I think so to red at 2 am 98.99998% sure
What we thought was a roar
Was merely a snore
The lion Atlantic is slumbering...
NHC
How ironic:
NHC Intellectual Property
LOL!!
Agreed.
99L goes from being a sure candidate for ana to complete and utter crap.
a tiny low heading toward the lesser antilies suddenly develops convection around barbados, and even though it is weakening now, don't be surprised if DMAX invigorates it further.
And, the GFS has predicted a monster storm to hit either the central gulf coast, NYC, North or South Carolina, and Bermuda, depending on the model run.
looks like something should spin up sometime soon, but i have no idea when or where ana will finally form.
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT MON AUG 10 2009
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
THE BROAD AREA OF LOW PRESSURE LOCATED JUST TO THE WEST-SOUTHWEST
OF THE SOUTHERN CAPE VERDE ISLANDS IS MOVING WESTWARD AT 10 TO 15
MPH. SHOWER AND THUNDERSTORM ACTIVITY REMAINS LIMITED THIS
EVENING. HOWEVER...THIS SYSTEM STILL HAS SOME POTENTIAL TO BECOME
A TROPICAL DEPRESSION DURING THE NEXT DAY OR SO. THERE IS A MEDIUM
CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.
A SMALL AREA OF LOW PRESSURE ASSOCIATED WITH A TROPICAL WAVE IS
PRODUCING DISORGANIZED SHOWERS AND THUNDERSTORMS NEAR THE WINDWARD
ISLANDS. DEVELOPMENT OF THIS SYSTEM...IF ANY...IS EXPECTED TO BE
SLOW TO OCCUR AS IT MOVES WESTWARD AT 10 TO 15 MPH. LOCALLY HEAVY
RAIN AND GUSTY WINDS SHOULD CONTINUE TO SPREAD OVER PORTIONS OF THE
WINDWARD ISLANDS THROUGH TUESDAY MORNING. THERE IS A LOW CHANCE...
LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
$$
FORECASTER ROBERTS/BROWN
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT MON AUG 10 2009
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
THE BROAD AREA OF LOW PRESSURE LOCATED JUST TO THE WEST-SOUTHWEST
OF THE SOUTHERN CAPE VERDE ISLANDS IS MOVING WESTWARD AT 10 TO 15
MPH. SHOWER AND THUNDERSTORM ACTIVITY REMAINS LIMITED THIS
EVENING. HOWEVER...THIS SYSTEM STILL HAS SOME POTENTIAL TO BECOME
A TROPICAL DEPRESSION DURING THE NEXT DAY OR SO. THERE IS A MEDIUM
CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.
A SMALL AREA OF LOW PRESSURE ASSOCIATED WITH A TROPICAL WAVE IS
PRODUCING DISORGANIZED SHOWERS AND THUNDERSTORMS NEAR THE WINDWARD
ISLANDS. DEVELOPMENT OF THIS SYSTEM...IF ANY...IS EXPECTED TO BE
SLOW TO OCCUR AS IT MOVES WESTWARD AT 10 TO 15 MPH. LOCALLY HEAVY
RAIN AND GUSTY WINDS SHOULD CONTINUE TO SPREAD OVER PORTIONS OF THE
WINDWARD ISLANDS THROUGH TUESDAY MORNING. THERE IS A LOW CHANCE...
LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
$$
FORECASTER ROBERTS/BROWN
While the QS shows a closed low definitely with 99L, does the low seem broad to you guys?
Nope its orange still.
Same as before, mainly because 99L is closed and well defined.
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