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Update On 93L/Provisional Tropical Storm Alex: "Less Than 20% Chance Of Becoming A Hurricane"
From the Wunder Blog:
A modest region of intense thunderstorms (Invest 93L)
is over the central Caribbean, a few hundred miles south of Hispaniola.
This disturbance has the best chance to become Tropical Storm Alex of
any system we've seen so far this year. We don't have any buoys near
93L, but pressures at the ground stations surrounding the storm are not
falling. A pass of the ASCAT satellite
over the Central Caribbean at 9:45 pm EDT last night revealed a modest
wind shift associated with 93L, but nothing at all close to a surface
circulation. Top surface winds seen by ASCAT were 15 - 20 mph. Water vapor satellite loops
show that 93L is embedded in a large region of moist air. The
atmosphere over the Caribbean has moistened over the past day, which
should aid development of 93L. Wind shear
is a low 5 - 10 knots. The high wind shear associated with the strong
winds of the subtropical jet stream are over the northern Caribbean,
too far north to interfere with development, but close enough to
provide good upper-level outflow for the storm. Visible satellite loops
show high level cirrus clouds streaming away from 93L to the northeast,
evidence of the upper-level outflow channel that is developing to the
storm's north. Sea Surface Temperatures are plenty warm, a record 29 -
30°C. The Madden-Julian oscillation (MJO) currently favors upward motion over the Caribbean, which will act to increase the chances of tropical storm formation this week. The Madden-Julian oscillation
is a pattern of enhanced rainfall that travels along the Equator from
west to east. The pattern has a wet phase with large-scale rising air
and enhanced thunderstorm activity, followed by a dry phase with
large-scale sinking air and suppressed thunderstorm activity. Each
cycle lasts approximately 30 - 60 days. When the Madden-Julian
oscillation is in its wet phase over a hurricane-prone region, the
chances for tropical storm activity are greatly increased. The main
negative for 93L continues to be lack of spin. The University of Wisconsin 850 mb relative vorticity analysis
is showing that spin at 850 mb (roughly 5,000 feet in altitude) has
increased over the past day, but 93L needs to acquire additional spin
before it can grow more organized. I speculate that it is this lack of
spin that contributed to the loss of much of 93L's heavy thunderstorm
activity last night. The storm is now going through a cycle where it is
building another respectable mass of heavy thunderstorms, and the
increased inflow of low-level air that will feed these thunderstorms
will likely enhance 93L's spin today. The Hurricane Hunters are on call
to investigate 93L on Wednesday afternoon.
Figure 1. Morning visible satellite image of the central Caribbean disturbance 93L.
Forecast for 93L
NHC
is giving 93L a 40% chance of developing into a tropical depression by
Thursday morning, which is a reasonable forecast. Given the storm's
current lack of spin and relatively modest amount of heavy
thunderstorms, the earliest I'd expect 93L to become a tropical
depression would be Wednesday afternoon, with Thursday more likely.
Wind shear is expected to be low, less than 10 knots, over the central
and western Caribbean this week. Water temperatures will be warm, dry
air absent, and the MJO favorable. I don't see any major impediments to
the storm becoming a tropical depression by Thursday, and it is a bit
of a surprise to me that the computer models have been reluctant to
develop 93L. The GFS, NOGAPS, and UKMET models do not develop 93L, and
the ECMWF model doesn't develop 93L until after it crosses the Yucatan
Peninsula and enters the Gulf of Mexico in a about a week. The current
(2am EDT) run of the GFDL model predicts 93L will be a weak tropical
storm in the Gulf of Mexico in five days; its previous run had 93L as a
major hurricane in the Gulf. Given all this model reluctance and the
current disorganization of 93L, I give the storm a low (less than 20%
chance) of becoming a hurricane in the Caribbean. Expect 93L to bring
flooding rains of 3 - 6 inches to Jamaica, eastern Cuba, and
southwestern Haiti today through Wednesday. These rains will spread to
the Cayman Islands and central Cuba by Thursday, and western Cuba and
Mexico's Yucatan Peninsula on Friday. The current run of the SHIPS model
has 93L slowing down late this week to a forward speed of just 6 knots
(7 mph) from its current speed of about 10 mph, in response to a
weakening in the steering currents. A trough of low pressure is
expected to swing down over the Eastern U.S. early next week. If this
trough is strong enough and 93L develops significantly, the storm could
get pulled northwards and make landfall along the northern Gulf of
Mexico coast in the oil spill region. This is the solution of the
Canadian GEM model. If 93L stays weak and/or the trough is not so
strong, the storm would get pushed west-northwestwards towards the
Texas coast. This is the solution of the ECMWF model. The amount of
wind shear in the Gulf of Mexico next week is highly uncertain. There
is currently a band of high shear near 30 knots over the Gulf, and some
of the models predict this shear will remain over the Gulf over the
next 7 - 10 days. However, other models predict that this band of high
shear will retreat northwards and leave the Gulf nearly shear-free. The
long-term fate of 93L remains very murky. My main concerns at this
point are the potential for 3 - 6 inches of rain in Haiti over the next
two days, and the possibility 93L could become a hurricane in the Gulf
of Mexico next week.
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Nice to see that BP sponsors the weather channels also :)
http://www.youtube.com/watch?v=4sRHd5pngWE
Clear weather...good.
Has to traverse a large area of upper level shear flowing SW to NE over the SE end of Cuba.
Projected tracks of the moment have high levels of diversity with 2 models taking the storm (if it becomes one) over the oil gusher.
http://www.skeetobiteweather.com/picservice.asp?t=m&m=93
Patience. The gulf will get a big one in July. I'm thinking 40% of the underwater plumes and 30% of the surface slick will be washed ashore and sprayed about in the 8-10 foot storm surge that comes along with a cat 4-5 storm.
Hispaniola and southern Cuba have mountain ranges that can cripple or stop this little storm.
TBT brings the asshat!
Truth be told, I can't wait for the network news coverage, the specials, etc. This type of thing sets our useless teevee era media personalities in double-down mode, bringing their end ever closer. I had already made a run to Costco for a mega pack of nukable popcorn, but it will save 'till July.
Good news indeed.
This hurricane season will amount to nothing solely because our storeroom is full and we are fully prepared for a catastrophic season. It's just the way.
If we had one can of SPAM and a pint of water on our shelves, we'd get CAT 5 after CAT 5.
Only tempers the situation; a tropical storm is powerful enough to push, spread and mix the oil onshore, over boom, in home.