Leslie

Good evening all,

Thought after the past week that there may be some curiosity about Leslie in the Atlantic. 
Now that I am finally back with the living and mostly rested after the bought with Isaac and a long line of long shifts, I should put something out about the tropics, good and bad, but not so bad. 
First graphic is the future track for Leslie and this system should remain out in the central Atlantic. There may be some action for Bermuda but mostly a fish storm. (The not so bad)

Thanks to CIMSS  Cooperative Institute for Meteorological Satellite Studies
Space Science and Engineering Center  /  University of Wisconsin-Madison 

The good is that behind Leslie a plume of dust from the Saharan Air Layer (SAL) is moving off the African coast and will be crossing the central Atlantic. This should subdue any development at least for the next week. 

Thanks to CIMSS  Cooperative Institute for Meteorological Satellite Studies
Space Science and Engineering Center  /  University of Wisconsin-Madison 

That's all I have for now. I hope all my friends along the Northern Gulf of Mexico have made it through Isaac unscathed, or with as little problem as possible. 
BC

Isaac heading for the Delta !UPDATE! 6AM

After heading home early I woke and saw that there appears to be an eye wall forming on Isaac south of the Mouth of the Mississippi. The first rain bands are wrapping along the coast as well. 

The storm may be undergoing some RI (rapid intensification) due to dry air to the north wrapping into the center. the proximity to landfall should limit the degree of strengthening. 

All my friends along the northern Gulf Coast should have completed preparations. Especially those that live in coastal communities, even as far east as the Big Bend of Florida. The storm surge will be fairly significant as Isaac makes landfall and the wave action will likely cause erosion to the beaches, and in the usual places along Highway 98 across the Florida Panhandle and coastal Alabama. Lets address the numbers on Isaac first, at 11 pm Isaac was located about 190 miles southeast of the entrance of the Mississippi River. The storm is moving northwest (310) degrees near 10 mph, and maximum sustained winds are 70 mph with gusts 75 to 80 mph, using a 1.2 to 1.4 gust factor. 

Below is a list of Watches and Warnings from the last NHC advisory.

The storm surge may be the highest risk to life and property as Isaac makes landfall. The following links are for Storm Surge Exceedance, neaning above the National Geodetic Vertical Datum, not mean sea level. Then the Storm Surge Probabilities, based on the same datum. 

The track of Isaac has held fairly steady since passing just south and west of Key West last night, likely between the Marquesas Keys and the Dry Tortugas National Park around 6 pm with a minimum pressure of 997.3 at the Key West International Airport. 

The storm has been gradually intensifying during the day and is nearing category one strength. Isaac has been churning over the Gulf of Mexico for a couple of days as indicated by the seas, buoy 42003 west of Ft. Myers has measured seas around 17 feet. The forecast is for a moderate category one hurricane at landfall with 80 mph sustained and up to 100 mph gusts. 

The above is a chart of the hurricane wind speed probabilities. You will notice that the likelihood of anything stronger than category one is at the highest value, 16 percent. 

This is a much weaker storm than Katrina, but should not be underestimated. The storm winds after passage away from Key West were higher than as the storm passed south of the island. The wind field is quite large as was seen with the winds from Northern Broward county through St. Lucie Counties along the east coast of Florida last night. Please be Weather Ready, and be safe. For current watches and warnings along with the fastest updates go to your National Hurricane Center website, and for local warnings, hurricane local statements,  and preparedness guides, go to your local National Weather Service web page at the point and click site. Also remember, your best source for weather information on the web ends with .gov not .com. :-) My last midnight shift for 5 weeks with a couple of extras thrown in for fun, I am ready for sleep. Will update tomorrow if I wake up in time for the land falling event. 
Let me know how the storm has impacted you through the comments section of the blog. 
Cheers,
Bill

Issac passes Key West.

It was a typical tropical storm event for Key West today with some really good winds, some decent rains, lots of palm frond's in the street. Some tidal flooding due to bands pushing water up onto the south side of the islands. Very little damage reported so far. 
As of 11 pm Issac was about 75 miles west of Key West near the Dry Tortugas National Park. 

Maximum winds from the Hurricane Hunter aircraft was 55 knots and Issac was heading west-northwest near 14 mph. Issac should slow its forward sped a bit and gain some strength as it bears down on the Gulf Coast of Louisiana / Mississippi. The maximum in the intensity forecast  is for a moderate to high category one hurricane before landfall. my experience with the Lower Mississippi River Forecast Center, National Weather Service WFO Slidell, and the Corps of Engineers, is that they are the best in the business. While working in Ft. Worth during the floods of 2011 I believe the City of New Orleans, and the State of Louisiana will keep their communities safe with Issac. 

The NHC track is slowly shifting west again:

The wind probabilities form NHC:

Keep checking your local National Weather Service Office website for hurricane local statements that will have information on closings, shelters, and evacuations in your area. 

I'm ready for this one to end now thank you very much! 

Issac Update August 25, 11pm

Good evening all,

Sleep deprivation has not won the battle...yet!
Issac has emerged off the northern Cuban coast and is still having problems with the terrain from the mountains over eastern Cuba. From satellite interrogation we find there is a hole in the convection along the land side of the storm. This is likely due to the mountain shadow produced  by down sloping winds moving with the storm. 

The mountain shadow is very clearly shown in the latest ASCAT satellite pass. The wind barbs are red as each barb is worth 10 knots, and the color coding may help. The green would be 30 to 40 knots, dark blue 20 to 30 knots, and ligth blue 10 to 20 knots. (Remember I'm a little color blind so I hope these colors are correct)

The forecast track once again is clustered around the global and mesoscale model consensus that has been in very good agreement even with the ECMWF for the past 6 or 7 runs. Now that the storm is on the north side of Cuba there is absolutely no reason to go against it. 

The time for preparations has passed for the Keys and the storm may pass just before high tide which will put the storm tide as high as 2 to 4 feet. High tide in Key West is 732 pm, and at Pigeon Key in the middle of 7 Mile Bridge is at 637 pm. The storm should be crossing over Key West around 5 pm and may intensify into a minimal category one hurricane as it passes the Lower Keys.

Key West Tides

Marathon, Pigeon Key Tides

From the National Hurricane Center:

A HURRICANE WARNING IS IN EFFECT FOR...* THE FLORIDA KEYS INCLUDING THE DRY TORTUGAS* THE WEST COAST OF FLORIDA FROM BONITA BEACH SOUTHWARD TO OCEAN REEF* FLORIDA BAY A HURRICANE WATCH IS IN EFFECT FOR...* THE FLORIDA EAST COAST FROM GOLDEN BEACH SOUTHWARD TO OCEAN REEF* ANDROS ISLAND IN THE BAHAMAS

A TROPICAL STORM WARNING IS IN EFFECT FOR...* THE BAHAMAS* TURKS AND CAICOS ISLANDS* THE FLORIDA EAST COAST FROM SEBASTIAN INLET SOUTHWARD TO OCEAN REEF* LAKE OKEECHOBEE* THE FLORIDA WEST COAST FROM NORTH OF BONITA BEACH TO TARPON SPRINGS...INCLUDING TAMPA BAY A TROPICAL STORM WATCH IS IN EFFECT FOR...* THE FLORIDA EAST COAST NORTH OF SEBASTIAN INLET TO FLAGLER BEACH* THE FLORIDA WEST COAST AND THE FLORIDA PANHANDLE NORTH OF TARPON SPRINGS TO INDIAN PASS

The thinking is that the track has settled down and should be far enough west to make for off shore winds through Tampa Bay. This would keep the risk of storm tides lower than if Issac were to track nearer to the coast. The big question in the forecast is intensity and location at landfall. The storm will head over some warm waters for a rather long period of time even before it reaches the Keys, and then over the southeastern Gulf of Mexico. For this reason I think the intensity forecast may be pretty good and have no reason to disagree. 

Keep checking your local National Weather Service Office for local hurricane statements which should include shelter and evacuation information for your local area. 

Issac quick update

As of 09z, 5 am this morning the storm has run up against an mid level vorticity that is lingering over the Florida Straits between Cuba and the Upper Keys. This has also brought the track forecast a little to the left and keeps the core off the northern Cuban coast. 
With this in mind the storm would have a better chance to gain some "juice" as it moves northwest, and therefore NHC is going to intensify the forecast to category 1 hurricane by the 36 hour forecast period. 
This will force a hurricane warning for the entire Florida Keys and Southwest Florida Coast. 
I will have to bow to the GFS model in so much as it keep banging on the forecast with little deviation, even if the reason was totally unclear as to why. 
There are still some issues with the intensity forecast in my eye, the vorticity to the northwest of Issac, and there are some terrain issues yet to be worked out for the next 24 hours or so. 
Issac is forecast to remain in the cat one range of intensity from 36 hours through 96 hours as it crosses the northern Gulf Coast near Mobile Alabama Thursday. On the current track even though it would be necessary to issue a tropical storm warning for Sarasota southward, but the good news is that mort of the winds will be offshore before the storm weakens and moves inland. 
I will try to update later, but this boy needs some sleep after I get the morning forecast out at 6am. 

Be prepared and be safe.

BC

Issac 8.24.2012 11 pm

Well the interaction of Issac with the mountainous islands along its path has proven to be good, bad, and ugly for the storm.  The initial interaction with the southern peninsula of Haiti actually helped the center of circulation consolidate this morning due to the dry air down sloping off the mountains and into the center of Issac. This enhanced the vertical circulation and inturn produced deep convection around a vorticity, becoming the main core of the storm. (the good)

The interaction with Haiti, slowing motion of the storm, and the down sloping winds have been added to the lift inside the core this evening, subduing the deeper convection. Issac will go through some fluctuations in intensity and a gradual reformation of the core once or twice during the passage across the island. 

Latest satellite image shows another burst of convection over the core with a distinct mountain shadow due to the winds down the mountains. 

 The aircraft found a flight level wind of 64 knots, and many measure by dropsonde of 55 knots or better. With that in mind, along with model tracks, NHC has decided to move the storm to the east and intensify the system which will trigger hurricane wording across the keys and south Florida including at least some of Tampa Bay and Melbourne NWS county watch areas. 

Be prepared for the worst, and know that the intensity forecast is highly suspect at this time due to the continued interaction with the mountains of Haiti and Cuba. 
Turn to your official watch and warning authorities, National Weather Service, and the National Hurricane Center for the latest updates. 

Issac Update 3

Good morning all,

The last 24 hours have revealed that Issac is a storm without a discernible core. The satellite imagery from Thursday evening showed several vorticity centers and no cohesive core. The mid level circulation is quite impressive and quite large. 
Overnight the G-4 aircraft flew a mission over the Atlantic waters  north of Hispaniola searching for the breadth of the subtropical ridge, while the P-3 NOAA Hurricane Hunter aircraft followed recently by the AF C-130 flew through the storm searching for the center of circulation.

 The image above is the composite water vapor with visible image from CIMSS and the interesting thing is that the transverse banding is occurring in the western convective cluster. This is evident by the feather like high clouds moving out of the bright overcast. These clouds show the outflow channel in the mid and upper level of the storm and is an indication that Issac may be consolidating a bit. The initial position has been shifted southward again and is at 16.2 north, 69.6 west which puts it south of Santo Domingo.  
The environment around the storm remains very hostile for development with highly sheared ares on the northwest and northeast periphery of the circulation. 

The shear trends are still introducing higher shearing around the storm. So I certainly do not think the storm will have an easy time moving northward, due to this sheared environment, not to mention the mountains of eastern Cuba. 

The last thing I will say this morning is that the initialization of the storm keeps moving south, the flights through the storm are having an extremely hard time finding the center of circulation, and the current track based on the past few days is showing a very distinct turn to the right. All on which is based on the models being clustered. So we will side with NHC for a weak tropical cyclone with plenty of moisture. Rain and wind are on the menu for the Keys, and the Islands of the Caribbean. Beyond that we need a definitive motion vector to emerge. 

 For arguments sake, which there has been a bit of this at my location overnight, if the storm moves northwest to north, and holds together enough to regain strength over the Gulf of Mexico, we may see the models have done a great job. Otherwise, if the storm remains on a more westward track, and passes over or near Jamaica, the forecast will change dramatically. With that being said, everyone along the Gulf Coast and Caribbean should be paying close attention to your local National Weather Service Office and the National Hurricane Center websites for official forecasts, watches, and warnings. 

Issac Night 2

Good morning all,

Going out on a limb tonight with the mention of dry air, shear, and hostile environment for further development. Looking at the diagnosis tools from CIMSS Cooperative Institute for Meteorological Satellite Studies Space Science and Engineering Center  /  University of Wisconsin-Madison, I think as plenty of others do in the tropical community, that the re-positioning of the storm center is due to the sheariing environment around the storm. From the shear tendency  tools we find that the shear over the past 12 hours around the storm has doubled. As to click on the link you'll see the current graphic, click on the -3hr tab in the menu to see previous versions. 

There is clearly a large influx of dry air surrounding Issac tonight indicated by the MIMIC TPW (Morphed Integrated Microwave Imagery...Total Precipitable Water) products. 

Many people much smarter than I have been talking about the dry environment around the storm  and the potential impact to development. 

As mentioned above the latest flight into Issac has found the center is further south and the tracks will obviously be adjusted in the 5 am update so will not even try to interpolate this at this time. Take a look at the National Hurricane Center site for the updated track and probabilities in the morning. 

Many people are talking about data and the forecast in a negative way. The maximum wind speed probabilities obviously are taking the data into account as they are not very robust with the intensity forecast for the storm. 

The highest hurricane probability is 38% for a category one storm in the 36 hour period. The reason for the forecast and track of Issac is the model output. With such good agreement this has to be taken into account as well. The spread in the track forecast is non-existent with the ECMWF as the only outlying model in the group. 

The ECMWF has been right of all the other for several days, but also has a robust system moving up the eastern Gulf of Mexico. With that being said the forecast takes all this information in. The official forecast is reasonable and responsible. The upper level winds near and around the storm are shown in the following graphic.

The next 24 hours should reveal the true nature of Issac and produce a better forecast solution. The latest CHGHUR message from NHC still has chance for a 100 knot storm in 96 hours. 
So we wait a little longer for more data and the storm to either get its act together or not. 
For the latest information for official impacts and forecasts please visit your local National Weather Service Office website, or the National Hurricane Center website. Please remember that the center line of the forecast has an error. I saw some news stories today the showed the line only, which is a disservice to you. Remember Charley and the cone, the entire west coast of Florida was in the forecast cone and media didn't pay attention to what the hurricane center was putting in the forecast, they just went with what made the highest impact. It is easy to remember...use (.gov) not (.com). Your tax dollars at work. :-)

Issac

Good morning all,

Sorry I didn't update this afternoon. Working a lot of overtime due to the staffing issues here so have had limited time outside work to produce my discussion. 

Issac has become better organized over the past 24 hours at least with the convection near the center. The outflow channels are still not well formed, and the environment around the storm is becoming extremely hostile for further development. The TUTT (Tropical Upper Tropopheric Trough) mentioned in last nights discussion is still lurking over eastern Cuba and the Windward Passage. 

Image thanks to CMISS... Cooperative Institute for Meteorological Satellite Studies
Space Science and Engineering Center  /  University of Wisconsin-Madison

The TUTT is the likely culprit for the added nearly 40 knots of shear in the environment to the east of the storm. 

Image thanks to CMISS... Cooperative Institute for Meteorological Satellite Studies
Space Science and Engineering Center  /  University of Wisconsin-Madison

The trough that passed across central Florida Tuesday is hanging around and  appears to have a reinforcing push heading southeast across the northern Gulf of Mexico which may be very good for moving the forecast track of the storm more to the east.

Finally, the forecast track has already been sliding ever so slightly right of the original offering, and the latest dynamical models are even more right than the consensus. This is good because the consensus will be influenced by a preponderance of the dynamical models to one side of the existing forecast tracks. In this case to the right or east of the current tracks. 

 Without the satellite enhancements...

Image thanks to CMISS... Cooperative Institute for Meteorological Satellite Studies
Space Science and Engineering Center  /  University of Wisconsin-Madison

The dashed lines are the dynamical plots, solid are the consensus.
So I think there will  be some changes in the track over the next 24 hours. 
As for the intensity for those that know a little about weather, a -33 C dew point depression at 500 mb, with a -7 C dew point depression from POES sounding data, in the environment to the east of the system would make that a difficult environment for tropical development. This was data from Polar Orbiting Environmental Satellite program at 09Z yesterday morning. From the water vapor imagery seen above it looks like there may be even more dry air ahead of the storm. 

So we are in a wait and see situation. The models have been in pretty good agreement but there may be some changes not to the agreement, but to the tracks in all the model output. I will update again tonight. Until then keep a watch to your local National Weather Service Office, and the National Hurricane Center, for official updates on watches and warnings as Issac continues to churn toward the Leeward Islands.
Cheers,
BC

Possible evolution of 94-L

Good morning all,

94-L in the Atlantic is taking shape as the potential Tropical Storm Issac. The latest model runs are aligning very well on track with some spread in intensity forecast. However...this is all contingent on the storm developing ad conditions coming together. As of 5:00 am NHC issued the first advisory on TD-9 as the system has become better organized overnight. 

From the National Hurricane Center...www.nhc.noaa.gov


AT 500 AM AST...0900 UTC...THE CENTER OF TROPICAL DEPRESSION NINEWAS LOCATED NEAR LATITUDE 15.2 NORTH...LONGITUDE 51.2 WEST. THEDEPRESSION IS MOVING TOWARD THE WEST NEAR 20 MPH...32 KM/H...ANDTHIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT COUPLE OFDAYS. ON THE FORECAST TRACK...THE CYCLONE SHOULD MOVE THROUGH THESOUTHERN LEEWARD ISLANDS AND NORTHERN WINDWARD ISLANDS WEDNESDAYAFTERNOON...AND EMERGE OVER THE EASTERN CARIBBEAN SEA BY THURSDAYMORNING.

The system is moving quickly to the west and will update later today with more information now that the storm has been initialized for the models. It may be possible that if the TUTT (Tropical Upper Tropospheric Trough near the western Bahamas may provide some added shear which may be a qualifier to limit intensification of the system but it is looking fairly healthy, especially for a developing storm. Expect that we will see tropical storm Issac this afternoon or evening. 
Keep tuned for updates and if you live along the Caribbean, Gulf of Mexico, or East Coast of Florida, its time to check that your hurricane preparedness kit is up to date! NOW PEOPLE! :-)

Check in with your local National Weather Service Office and the National Hurricane Center, and Bill's Weather Blog for continuing updates on the evolution of TD-9 (Issac).