31 August 2008

Gustav heading for Louisiana, Hanna heading for the Bahamas, TD9 ready to form...

Gustav underwent rapid intensification Friday evening through Saturday afternoon.  In 24 hours ending 00Z Sunday, the central pressure fell 34mb, and in 23mb in 12 hours.  It strengthened from a 60kt tropical storm to a 130kt CAT4 hurricane in 27 hours.  Unfortunately, it accomplished this while heading for, and passing over, western Cuba, causing extensive damage.

Since exiting Cuba, it has had a hard time reorganizing, though still a 100kt CAT3 hurricane.  It is heading NW at 15kts, toward the central LA coast, and landfall is expected Monday morning as a major hurricane near Marsh Island.  However, there is still uncertainty, and a hurricane warning covers the LA and MS coasts.  As far as Katrina-ravaged New Orleans goes, so far about 15,000 people have evacuated, and evacuation orders are still in place for the city.  Lake Pontchartrain can expect a 15-20 foot storm surge on Labor Day, which will certainly re-test the levee system protecting the below-sea-level city.  Other parishes in coastal LA also have mandatory evacuation orders.  As of this writing, over 3/4 of oil production in the Gulf has ceased, as platforms and rigs are evacuated and shut down for the duration of the storm.

The latest intensity is 100kts and 962mb.  It is forecast the strengthen a bit more again, perhaps to CAT4 status, before landfall.  It's currently looking ragged on satellite, lacking a clear eye, showing signs of southerly vertical shear, and has dry air wrapping around west and south of it.  The main factor in its favor is deep, warm water under it.

You will be able to track its progress toward the coast via radar loops that I'm generating... a long and short range from New Orleans, and a short-range from Lake Charles (all are available at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/atlantic/).

Hanna, still maintaining modest tropical storm intensity, is strongly sheared.  Latest intensity is 45kts and 999mb, and heading WNW at 9kts.  It's now a couple degrees north of the Turk islands, and it is expected to track slowly westward toward the Bahamas, then NW toward the southeast US coast as a hurricane.  Landfall could be sometime next weekend... however, the steering environment is incredibly complicated, and Hanna will just have to be watched for the next few days to figure out where it's going!

The easterly wave I mentioned 2 and 3 days ago near the Cape Verdes has gotten better organized and is now located near 16N 35W.  Development of this wave should be slow as it heads W at 12kts.  The next name on the list is Ike.

Please visit my tropical Atlantic headquarters.

29 August 2008

Gustav exits Jamaica, Hanna gaining strength also...

First of all, today marks the 3-year anniversary of the final, historic, and infamous landfall of Hurricane Katrina.  Katrina was a Category 3 hurricane when it came ashore near the LA/MS border.  It was responsible for 1833 deaths, and $81 billion in damage.  Though not in the running for the deadliest landfall, it did set the record for the costliest landfall, and costliest natural disaster for that matter, in US history.

Another bit of history to point out as we look ahead to the holiday weekend is the infamous Labor Day Hurricane of 1935.  This storm mostly affected the Florida Keys, and was the most intense (by pressure) US landfall on record... Camille was #2, Katrina was #3, and Andrew was #4.  It was responsible for over 400 deaths and it basically obliterated Islamorada and other towns/keys in extreme southwest Florida.  Fortunately, residential air conditioning wasn't affordable or practical yet and Florida was barely populated compared to today (during the 1950's, the state's population grew by 79%, largely because of A/C!).

Now back to 2008.  Gustav has completed its trek over Jamaica, but has already caused at least 59 deaths across Haiti, Dominican Republic, Jamaica, and Cuba.  It is now over open, deep, warm water and poised to intensify to a powerful hurricane as it heads WNW toward western Cuba, then into the Gulf of Mexico.  As of 15Z today, the intensity is 55kts and 988mb and is located 165 miles from Grand Cayman.  It has sped up a little and is now moving WNW at 7kts (has been 3-4kts lately).  All conditions and current appearance suggest rapid intensification is primed to take place.  The latest satellite images indicate that an eyewall is forming already.

So of course, the question is what about landfall?  The western tip of Cuba is the next target probably on Saturday evening as a strong hurricane.  Then the US gulf coast is next, probably Tuesday morning as a very strong and dangerous hurricane.  The current NHC forecast track is centered on the middle LA coast, but anywhere from Corpus Cristi, Houston, New Orleans, Panama City is within the 5-day average track error cone.  Coastal residents within this range should at least begin basic preparations.

Hanna is still a tropical storm as well, and like Gustav, is on an intensification trend.  TS Hanna is moving WNW at 10kts and intensity is estimated at 45kts and 1000mb.  It is forecast to continue strengthening, and slowing as it heads WNW... then by the end of the weekend, start turning SW toward the Bahamas.  A long-range model run, shown here, forecasts Hanna to then turn westward, enter the Gulf, and make landfall on LA late next week as a strong hurricane. This plot is valid Friday evening (Sept 5):  http://www.ecmwf.int/products/forecasts/d/getchart/catalog/products/forecasts/medium/deterministic/msl_uv850_z500!Wind 850 and mslp!192!North America!pop!od!oper!public_plots!2008082900!!chart.gif

Elsewhere, the easterly wave that exited the African coast yesterday is now just east of the Cape Verdes and still looks impressive on satellite.  Central pressure of the Low associated with the wave is estimated at 1007mb.  This will likely be the next named storm in a couple days: Ike.

Please visit my tropical Atlantic headquarters.

28 August 2008

Gustav heading for Jamaica, Hanna forms...

After crawling across Haiti's southwestern peninsula and almost losing tropical storm status (it weakened to 40kts and 999mb yesterday), Gustav is now back over water, but made a remarkable turn in the last 12 hours or so.  Rather than the expected westward track which would have put it along the southern edge of Cuba, it turned southwest and is now east of Jamaica and should end up passing over or SOUTH of Jamaica!  From that point, the previous forecast track remains unchanged: clip the extreme western tip of Cuba (or miss it by a little), then enter the central Gulf, then head NW toward Louisiana.  The official forecast, which agrees with many models, is for a major landfall on Labor Day in/near Louisiana.

As of 15Z, Gustav was located on the eastern tip of Jamaica, with an intensity of 60kts and 983mb... nearly a hurricane again.  It appears to be forming another eye, but the mountains of Jamaica could disrupt that later today.

The HWRF forecast is shown at (surface winds and sea level pressure):
It is forecasting an extremely intense hurricane in the Gulf and at US landfall... reaching it's peak intensity of 894mb and 137kts on Sunday evening.  If this verifies, it could rival the infamous Labor Day Hurricane of 1935.  As usual, do not focus on the exact track... the 3-5 day range has too many uncertainties, but should be used as a guideline for preparedness.  Certainly anyone in coastal LA, MS, AL should at least be preparing for this.

The disturbance that was near 20N 57W yesterday was upgraded to TD8 early this morning, then TS Hanna later this morning.  Latest intensity is 35kts and 1002mb and it's located near 20N 59W.  it is forecast to gradually intensify to hurricane status and head westward toward the US east coast in a week or so.  At its somewhat far north location, it would be easy for it get recurved by a mid-latitude trough though.

And, a new easterly wave has exited Africa (near 18W) and is already quite impressive.  It will be watched for further development.  The next name on the list is Ike.

Please visit my tropical Atlantic headquarters.

27 August 2008

Gustav temporarily weakens over Haiti...

At 03Z last night, Gustav was downgraded to a Tropical Storm, and is still at that status, as it passes over the high mountainous terrain of Haiti's southwestern peninsula.  And it's doing so very slowly (~4kts).  The flash flooding there must be terrible.
An AP report from Haiti states "rising water was threatening crops in Haiti, already a powder keg because of spiking food prices. Earlier this year, there were deadly protests over the high cost of food.  Gustav lingered over the nation's impoverished and deforested southern peninsula, threatening banana and vegetable fields.  Residents in coastal Les Cayes ignored government warnings to seek shelter, instead throwing rocks in protest of Haiti's poor economic conditions".  Not a good situation.  And now Gustav is eyeing up Cuba, Jamaica, and the Cayman Islands.

The western tip of Cuba could have a brush with an intense Gustav on Saturday, then the storm enters the central Gulf of Mexico, where it's forecast to gradually start turning toward the NW.  Presently, Louisiana is a likely target on Monday, but the situation will of course be very carefully watched and forecasts will be tweaked.

The HWRF model (WRF model that's coded to specialize in hurricanes) has the following forecast out to 5 days (the fields shown in the large plot are sea level pressure in the line contours and vorticity in the shaded contours... and in the zoomed plot are sea level pressure in the line contours and surface wind speed in the shaded contours):
LARGE: http://einstein.atmos.colostate.edu/~mcnoldy/tmp/gustav/gustav_absv_p.gif
ZOOMED: http://einstein.atmos.colostate.edu/~mcnoldy/tmp/gustav/gustav_wind_n.gif
HWRF shows a peak intensity of 901mb  and 135kts late this weekend, and a major landfall very similar to that of Camille and Katrina.  The official NHC forecast currently agrees very well with this scenario, but it's still 5-6 days out.

The easterly wave that was near 20N 56W yesterday has barely moved and is now near 20N 57W.  It's estimated at 25kts and 1009mb, and although vertical shear has made development a challenge these past few days, it is forecast to lessen and allow this system to get better organized.  The one near the Cape Verdes is lacking organized convection now, but will still be watched closely.  This is the time of year when a lot can happen at once!

Please visit my tropical Atlantic headquarters.

26 August 2008

Gustav now a hurricane...

Not only is Gustav a hurricane, it's almost a Category 2 hurricane already!  The central pressure has fallen 25mb in 24 hr, and 9mb in 12 hr.  Certainly not extremely rapid intensification (yet), but fast enough to warrant concern.  In microwave imagery and aircraft recon data, there is a small eye/eyewall too, but no open eye is yet apparent in visible or infrared imagery -- that could change in a few hours though.  You can monitor a high-resolution visible satellite loop here:

The latest intensity (15Z) is 80kts and 981mb, with significant intensification expected over the next week.  It should weaken a little bit as it passes over the southwestern peninsula of Haiti, but the ocean is so incredibly warm and deep under Gustav's predicted path (combined with little to no vertical shear), that there's no foreseeable reason that this will not be an extremely powerful hurricane in a few days.

As far as the track goes, things aren't looking good for Cuba or the US.  A major hurricane landfall on the US Gulf coast looks inevitable, but this far out, it's too hard to say where along the coast.
The GFDL model's 06Z run paints an ominous picture for Lousiana and Mississippi:
This is one model and one run, and 5 days out, but a situation worth preparing for nevertheless.

Just for the record, you first heard about what's now Gustav in my August 14 update: "
an impressive easterly wave has just exited the African coast and is just south of the Cape Verdes now.  Several long-range models develop this into a hurricane within a week".  Then again in the August 18 update: " The easterly wave I first mentioned four days ago is now near 35W and heading W at 12kts.  There is a 1009mb Low embedded within the wave, and its satellite presentation is impressive.  In the long term, it looks like continued W-WNW motion and gradually strengthening".  Gustav has been a long time in the making.

Elsewhere, we have a couple other areas of potential development.  One near 20N 56W (we've been discussing that one for a long time now), and one that recently exited Africa near the Cape Verde Islands.  The first has a 1011mb Low with it and is moving WNW, and the second has a 1008mb Low and moving WSW at 10kt.  The next names on the list are Hanna and Ike.  Ike replaces Category 3 Isidore (2002) that caused so much destruction on the northern Yucatan Peninsula, and then moved straight north into New Orleans as a tropical storm.

Please visit my tropical Atlantic headquarters.

25 August 2008

Fay gone, Gustav forms...

Long-lived Fay finally dissipated this past weekend, but not without drenching Florida and the southeast.  Past storms like Agnes '72 and Allison '01 come to mind when talking about weak systems that are slow and dump amazing amounts of rain.  You can view the estimated rainfall over the past week at http://water.weather.gov/index.php?layer[]=0&layer[]=1&layer[]=4&timetype=RECENT&loctype=STATE&units=engl&timeframe=last7days&timeYYYY=2008&timeMM=8&timeDD=25&product=observed&loc=stateFL

The easterly wave we were watching last week was upgraded to TD7 on Monday morning, then quickly upgraded again to TS Gustav, the seventh named storm of the season.  The intensity as of 21Z is 50kts and 996, tracking WNW at 12kts.  It is forecast to continue moving WNW and possibly intensify very quickly.  There is great disagreement between forecast models and the NHC forecast, so for now, I'll leave the details out.  The countries in its 3-day future are Haiti, Cuba, and possibly Jamaica.  If this storm manages to remain over ocean for longer than expected, it could become very intense given the ideal environmental conditions.

Elsewhere, there's a weak wave near 23N 56W, but vertical shear is strong over that system.

Please visit my tropical Atlantic headquarters.

19 August 2008

Fay inland over Florida and strengthening...

Fay made landfall on the Florida peninsula near Cape Romano (about halfway between Fort Meyers and Cape Sable) at 09Z this morning as a 50kt tropical storm.  However, since making landfall, it has developed an eyewall and the central pressures have fallen to 986mb (was 989mb at landfall, and 995mb a few hours prior to landfall).  Though the winds are not very strong at surface stations across the peninsula, they could start to increase in response to the decreasing pressure.

Visible satellite loop:

Radar loop:

The forecast is still uncertain.  The official forecast does bring Fay up to minimal hurricane strength, while tracking it northward over the peninsula, then westward over southern GA/AL.  http://www.nhc.noaa.gov/storm_graphics/AT06/refresh/AL0608W5+gif/094742W_sm.gif

But, as you can see here: http://euler.atmos.colostate.edu/~vigh/guidance/northatlantic/track_early1.png, there's a still a bit of model differences in the forecast track.  Some models bring it up to hurricane strength, even approaching CAT2-3 at landfall near the GA/FL border in a couple of days.

The easterly wave we've been tracking (exited Africa on Aug 13) is now at 38W and forecast to continue heading WNW and gradually strengthening.  This could be a big player in a week or so.  The next name on the list is Gustav.  

Please visit my tropical Atlantic headquarters.

18 August 2008

Fay heading for Florida...

During the weekend, Fay maintained tropical storm intensity while passing over Hispaniola and then central Cuba.  As of this writing, the circulation center has just exited Cuba and is now over very warm water south of the FL Keys.  Intensity as of 15Z today is 50kts and 1003mb, and it's moving NNW at 11kts.  SSTs under the storm are around 30C, and vertical shear is moderate: westerly at  10-15kts.

You will find a radar loop from Key West at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/fay08/Fay_18Aug08.gif

Also, you can monitor surface observations from Marathon FL at

Fay is forecast to pass directly over the Keys later today, as a tropical storm or possibly even a minimal hurricane, then continue north toward Tampa, making landfall there tomorrow morning (local) as a CAT1 hurricane.  The latest watches/warnings are shown graphically at http://icons-pe.wunderground.com/data/images/at200806_alerts.gif
After this west peninsula landfall, the long-range forecast isn't so straight-forward (some models take it on a north track inalnd over GA, others take it back over ocean and then into coastal GA/SC, while others take it for a loop off the east coast of FL, then back inland).  But let's get past this one first!

The easterly wave I first mentioned four days ago is now near 35W and heading W at 12kts.  There is a 1009mb Low embedded within the wave, and its satellite presentation is impressive.  In the long term, it looks like continued W-WNW motion and gradually strengthening.  This could be upgraded to TD7 today, and the next name on the list is Gustav.  There's also a wave right on its heels, near 25W which will also be watched closely for further organization.

Please visit my tropical Atlantic headquarters.

15 August 2008

Disturbance upgraded to Tropical Storm Fay, now near Hispaniola...

Yesterday through the present time, it tracked over the Virgin Islands, Puerto Rico, and is now over extreme eastern Dominican Republic (the eastern country on the island of Hispaniola).  Latest intensity is estimated at 35kts and 1009mb, and heading W at 14kts.  The track over Puerto Rico, Hispaniola, and eventually Cuba will certainly stall substantial intensification, but any opportunity over open water could be rapidly taken advantage of.

The track forecast has been most well-handled by the leading Canadian model, which has shown this system moving south of Cuba and into the Gulf of Mexico, while all of the others either recurved it east of Florida or up the eastern FL coast.  It's showing no rush to recurve, and is on a straight west heading, plowing right through the Greater Antilles.  Now, more and more models are indicating a path over or south of Cuba, then along or west of the FL peninsula.
A recent run from GFDL is shown here: http://moe.met.fsu.edu/cgi-bin/gfdltc2.cgi?time=2008081512-invest92l&field=Sea+Level+Pressure&hour=Animation (sea level pressure is contoured, runs out to 7 days)
This scenario has Fay passing south of Cuba, intensifying, THEN heading north toward the FL panhandle while intensifying, finally making landfall next Wednesday evening as a CAT3 hurricane.  This IS NOT an official forecast, just one model run, but something that warrants a close eye nonetheless.

The other easterly wave we've been watching for some time now is on its heels near 50W.  It's still disorganized, but is becoming more convectively active with time.

Please visit my tropical Atlantic headquarters.

14 August 2008

Depression nearly formed near Virgin Islands...

Though still not officially a Depression, the easterly wave we've been watching closely is now passing north of Barbuda and toward the Virgin Islands.  You can view a radar loop of the forming storm from the Guadeloupe radar at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/fay08/Fay_14Aug08.gif

It has entered the phase where it can intensify rather quickly, a phase visually triggered by the development of a persistent CDO, or cold dense overcast.  On an infrared satellite loop, this looks like a shield over the center, with very cold cloud-top temperatures, roughly -75C in this case.
Under this dense cloud shield aloft, a core of intense thunderstorms is organizing, perhaps even into an early eyewall (see radar loop above).

Current intensity is estimated at 30kts and 1009mb, and tracking WNW at 12kts.  The forecast is looking more and more ominous for the US, and first, the Bahamas.  Computer models indicate a track directly over the Bahamas, maybe as a CAT1 hurricane this weekend.  By early-mid next week, the southeast US coast should be on alert... from FL to NC.  There is a smaller possibility that it could slip south of Florida and cross into the Gulf.  The forecast track will of course be closely scrutinized in the coming days.

The next number/name on deck is 6/Fay.

Elsewhere, an impressive easterly wave has just exited the African coast and is just south of the Cape Verdes now.  Several long-range models develop this into a hurricane within a week.

Please visit my tropical Atlantic headquarters.

12 August 2008

Two easterly waves tracking across the basin...

Although there are no named storms at the moment, I wanted to point out a couple easterly waves.  One is centered near 54W, and the other near 31W.  Both have Lows associated with them, with approx 1008mb central pressures, and both are traveling W-WNW at 10-15kts.  You can track them in 12-hourly satellite images at:

The western one is forecast to gradually turn more westward, and be just north of Hispaniola in 4-5 days.  The eastern one is forecast to continue heading WNW-NW.  Both should strengthen, but the western one is favored... AND of more concern to the US.  By week's end, a 5-day forecast could be quite revealing: is it destined for a landfall or not?

And what exactly IS an easterly wave?  First of all, it's "easterly" because it travels from east to west, with the trade winds (the equatorial/tropical belt of winds that blow from east to west all year long).  The "wave" part has more interesting origins.  Large temperature differences between the desert and rainforest regions of continental Africa generate a strong low-level jet, or plume of enhanced winds.  This jet is unstable, and tends to break down into discrete waves, with ridges and troughs.  The troughs are what we then call "easterly waves", and are characterized by lower pressures and thunderstorms.  The jet is most active in the August-September timeframe, but is present from April through November.  As you've probably noticed, not all easterly waves develop into tropical cyclones.  Roughly 60 easterly waves track across the basin each season, but on average, only 6 or 7 of them might become tropical storms or hurricanes.

Please visit my tropical Atlantic headquarters.

05 August 2008

Edouard makes landfall...

Edouard made landfall as a 55kt tropical storm Tuesday morning around 7am CDT, between Sabine and High Island TX ... right by the Louisiana border.  Fortunately, this area is not very populated.  Jefferson County, where landfall occurred, has about 240,000 residents, compared to about 4 million in the three neighboring counties to its west.  However, in the same county, about 1 in 5 people live at or below poverty level, so even a weak storm can have a very negative effect.  Incidentally, this is almost exactly where Rita made landfall 3 years ago, but as a Category 3 hurricane with 105kt winds.

So far, no major damage reports have come out, and no deaths... just half a foot of rain and moderate gusty winds that have taken down some trees and power lines.  The rest of the basin is quiet right now, and probably will be for a little while longer.

Please visit my tropical Atlantic headquarters.

04 August 2008

Edouard forms near northern Gulf coast...

On Sunday afternoon, TD5 formed in the north central Gulf of Mexico.  It is currently just south of New Orleans and heading W at 7kts... near 28.2N 90.6W.  Intensity is 40kts and 1002mb.  It's battling some northerly wind shear and ambient dry air, which should both act to at least slow intensification.  But SSTs are quite warm under its future track.

Latest SST analysis:
Latest vertical shear analysis:

A Tropical Storm Warning and a Hurricane Watch are in effect for the northern half of the TX coast and the western half of the LA coast.  Edouard is not forecast to be a hurricane at landfall, but it's certainly not out of the realm of possibilities.  It is heading generally westward toward Houston, and should make landfall early Tuesday morning.

Please visit my tropical Atlantic headquarters.