Weak Mid-Atlantic Disturbance Turns Into Named Storm

After a brief increase in development chances yesterday from the NHC, it seemed as if the subtropics were going to be dormant for at least a few more days. And then development chances shot up this morning, and then Tropical Storm Claudette was born this afternoon. This was well forecast by the mesoscale models whether Claudette wanted to be late to the party or not as far back as 48 hours ago. The system evolved over North Carolina as a frontal system with a slight dip in central pressure on Saturday evening. Since then, the system went over the loop current with 80°F+ water surface temperatures. Fronts dissolved overnight and a tropical cyclone…with 50 mph was born.

071315 Claudette RGB Loop

It wasn’t too much of a surprise that this system had winds of 45-50 mph. The mesoscale models had a weak tropical storm while the system was over the eastern US. Even the global models had a weak reflection of a warm-cored system with a closed center. HRRR notably had development and/or intensification pegged by yesterday afternoon. The below ASCAT imagery from this morning confirmed that thought process. Because of the small spatial size of this system, it is no shock that the smaller scale models did better this time around when compared to the global models.

ASCAT imagery from 14z this morning

ASCAT imagery from 14z this morning

Current Information: 

  • Winds: 50 mph
  • Pressure: 1004 mb
  • Movement: NE at 17 mph

The good news for eastern Canada is that Claudette is quickly moving into an area of strong and intensifying shear. Combined with considerably cooler water, this tropical storm will become post-tropical by Wednesday at the latest. Satellite imagery is already showing an exposed center. Claudette is expected to continue to accelerate toward the northeast and toward the eastern end of Nova Scotia and Newfoundland.

Even as this system is quickly removed from our memory as a short-lived tropical system by midweek, it does bring up a good point for what will likely be a season of non-MDR/non-deep tropics type systems. With the large convective squall line crossing the Midwest and central Appalachians today, one has to think that these continental systems may be a decent source of (sub)tropical systems this year. At the very least, there is a cool front coming down the Appalachians this week with embedded shortwaves/energy that should be watched for both severe weather and maybe even tropical weather. In fact, this system ends up in exactly the same spot in 84 Hours. Obviously this time it looks frontal however.

18z NAM at 84 Hr

18z NAM at 84 Hr

It will be interesting to see how far south that front comes. Some indications show that this front could come as far south as south Georgia with increasing weekend rain chances and decreasing temperatures for Georgia, Florida, and the Carolinas. Getting into that new phase will probably result in more severe pulse-type systems than normal.

Current Squall Line in the US

More than 500 reports have been recorded at the SPC between yesterday and today[below] from central Minnesota to North Carolina. These reports will probably continue into the Carolinas and much of the southeast through Wednesday. The moderate risk continues into the overnight hours in a secondary line well to the northwest, close to the location where the current squall line began.

071315 SPC Reports

 

News: You may see a few changes in how this site is arranged over the next few weeks, and you can now find me on Instagram!

Hope to see you there and on Twitter as always, @JonathanBelles. Quite a roller coaster this trough is. Hopefully you’ll join me for the ride! I’ll be watching the rediscovery of Pluto tomorrow as well with New Horizons.

–Jonathan

The Atlantic is Clear, But The Tropics are Very Active Out West

The second month of the hurricane season continues to be inactive in the Atlantic, but July is shaping up as a very active month for the western two-thirds of the Pacific.  It has been more than two weeks since Tropical Storm Bill crossed the United States. The Atlantic seems to have collected every piece of meteorological calmness it can: high vertical wind shear, basin-wide dry air, and some cooler waters in the development region. There is a large contrast in the Pacific Ocean where three tropical cyclones are already crossing the basin and one disturbance may have some impacts on Hawaii in the next week. I’ll get to that forecast, but first I want to start in the Atlantic.

Atlantic water vapor imagery from July 6th

Atlantic water vapor imagery from July 6th. Expand loop by clicking on satellite image

On the water vapor image above there are a few things to note (in no particular order):

  1. There are two upper level lows, one north of the Turks and Caicos and the other in the eastern Gulf of Mexico. These are well developed, and they both keep a lid on tropical development. Both ULL are expected to crawl west of west-southwestward over the next few days. Both will slide unfavorable dry and sheared air into the Gulf, Western Atlantic, and Caribbean.
  2. The jet is anticipated to lay across the Caribbean this week with 100 kt of shear. You can see the effects of a currently much weaker shear just east of the Lesser Antilles, but much stronger high level winds (30-40 kt at 100-200mb) are currently in place. Some divergence is assisting this activity.
  3. Extended Saharan air layer and otherwise dry air across the basin. This is visible on the loop above in the reddish-brown color. Large plumes of this dry air are coming from Africa and continue to travel across the Atlantic with tropical waves and the ULL. You can see the extent of the dust in the modeled image below. Even the thinner, or blue/light purple, dust can be seen in the skies above the Caribbean and Gulf coasts as a haze.Sunsets and sunrises are likely red in the heartland of the US where this dust is mixing with smoke from fires in Canada. The more thick the dust layer is the more detrimental that layer is to tropical cyclones
Dust across the Atlantic as modeled by NASA for this evening.

Dust across the Atlantic as modeled by NASA for this evening. Provided by WeatherBell

It is pretty obvious that tropical cyclone activity will remain low through at least five days , and probably through 10 days. The NHC agrees with this sentiment. A secondary source for development may be the MCS train that has been traveling toward the east coast through the southeastern US. The waters in the Gulf of Mexico are very warm and supportive for development should atmospheric conditions get more favorable.

Gulf of Mexico water temperatures in Celsius.

Gulf of Mexico water temperatures in Celsius.

The Active Pacific

Counting below from China eastward there are three tropical cyclones: TS Linfa, Typhoon Chan-Hom, and Typhoon Nangka. All three are forecast or are currently causing troubles from the islands of the western Pacific and/or the Chinese mainland. The typhoons are both expected to intensify as the move west-northwestward. Nangka is expected to cross waters to the north of Guam midweek.

070615 Wide Pacific IR

Much farther east, the central pacific hurricane center will likely be busier toward midweek as well. Move two blobs southeast of the Hawaiian chain and you can see an organizing invest 96E. That system currently has a high chance of development. Current forecast models bring this system to the north of the islands toward the end of the week as a minimal tropical storm. Slow development is expected with 96E. The next name on the CPHC name list is “Ela”.

Long Term Signals (and Geek Signals): 

Note: If you have no knowledge of atmospheric waves, read this recent blog post by the National Hurricane Center first: https://noaanhc.wordpress.com/2015/06/25/the-ups-and-downs-of-predicting-tropical-cyclone-formation-the-role-of-atmospheric-waves/

The long term wave signals that climatologist and meteorologists like to use for long term forecasts are very supportive for Pacific activity through this week, but fall flat as the signal is investigated farther east. Below are the Madden-Julian Oscillation from the GFS and Euro Ensembles. Note that the signals are opposite in propagation direction, but the end result is a nearly muted (within the center circle) for favorability in any basin. For the Atlantic we want to see the signal in the left side of the diagram. For Pacific cyclones, we want to see the signal in the upper part of the diagram. Note that the distance from the center of the diagram is a direct representation of the favorability of the MJO signal. Looking at the diagrams, they both show very favorable signals for the western Pacific. We have three tropical cyclones there now. If the GFS is correct, activity will be increased slightly toward Oceania closer to July 20th, but if the Euro ensembles are correct then the eastern Pacific may see a slight increase in activity next week. The Atlantic shouldn’t seek much of any help from this signal.

070615 MJO Signal

The Kelvin wave forecast shows a slight increase in activity for the eastern Pacific and western Atlantic basins during the middle of the month. Important: These global waves are only creditable for general trends in tropical activity. The Atlantic will have to moisten and shear will have to lessen before any substantial activity can occur. My current forecast is for no tropical activity through July 15th with a fairly high confidence.

More updates as always on twitter @JonathanBelles,

Stay safe,

–Jonathan

Tropical Storm Bill: Cross Country Rain Maker

The second tropical storm of the 2015 Atlantic Hurricane Season will likely be known as the second drought buster that did more harm than good, and then kept going. Just about two weeks ago, a previously upper level system moved into central Gulf of Mexico from the far western Caribbean and had worked its way down to the surface with tropical storm force winds. Even as a warm-colored blob on the hurricanes.gov webpage, scatterometry wind analyses showed that tropical storm force winds expanded into a sizable portion of the Gulf. The eastern semicircle of 91L was very much like a tropical storm with the aforementioned winds and plentiful convection. It took numerous hurricane hunter flights in order to close off a closed low, which didn’t happen until June 15th.

Note: This post may contain some opinions, and these are my opinions alone. They do not reflect the opinion of any government, public or private agency.

Full Bill track. Data from NOAA, track from Wikipedia

Full Bill track. Data from NOAA, track from Wikipedia

Leading up to this nearly late classification, there were some wranglings on social media about the social science applications of the definition of a tropical cyclone. In this instance, the “closed surface wind circulation about a well-defined center” (NHC) was deemed by many as being in the way of offering tropical storm advisories onshore and marine areas. Coastal flood warnings, gale warnings, and flood watches were replaced in part by tropical storm warnings upon formation 155 miles SSE of Galveston, TX. This is sort of the reverse of the Hurricane Sandy situation. NHC continues to work on these policies, and we should see changes in the next couple of years.

Even while we were pretending that this was a tropical storm without a name, the forecast for this system was well done with the exception of one slight westward jog as named Tropical Storm Bill approached the coast around midday on June 16th. These jogs are pretty hard to forecast. The two driving points during this tropical system’s approach was the flood potential and potential for Bill to go well inland as a tropical cyclone. Satellite imagery below showed that Bill had a characteristic strong feeder band on the eastern and southern sides.  That band also reignited with severe weather and other convective activity as it approached the mid-Atlantic.

Bill’s Bath in Texas

Flood watches of a few flavors were issued in the days leading up to landfall. As Bill made landfall on Matagorda Island just before noon, a strong feeder band set up shop in extent from just west of Houston to southeast of Corpus Christi mainly offshore. As advised by the WPC’s final advisory, the top ten rainfall amounts from Bill were:

  • 12.53″ in Healdton, OK
  • 12.50″ in Montague, TX
  • 11.77″ in Ganado, TX
  • 11.52″ in Newport, OK
  • 10.09″ in Burneyville, OK
  • 9.51″ in Kirbyville, TX
  • 9.17″ in Sealy, TX
  • 9.03″ at Alice Int’l Airport, TX
  • 8.63″ in Sulphur, OK
  • 8.57″ in El Campo, TX

Rainfall amounts of 4″ or more fell in 8 states.

7 day rainfall ending on June 23rd at 7am CT.

7 day rainfall ending on June 23rd at 7am CT. Click for full size

Water rose roughly 3 feet above normal as Bill came ashore at Port Lavaca, TX according to the landfall notice. Two deaths in the United States are at least indirectly attributed to flood waters including a two-year old boy and an 80-year-old woman. Both deaths were in Oklahoma. The woman may have tried to drive through flood waters which, in combination with a very wet May, were caused by Bill. Source: http://bigstory.ap.org/article/0a20616725b9472393a01026e1ffb05f/midwest-braces-remnants-bill-texas-spared-worst

Tropical Storm Bill Moving through TX and OK. Radar Loop from Brian McNoldy, Univ. of Miami, Rosenstiel School

Tropical Storm Bill Moving through TX and OK. Radar Loop from Brian McNoldy, Univ. of Miami, Rosenstiel School

The Long Tracker

As a tropical cyclone, Bill tracked across six states and affected more than a dozen additional states. It’s final track point as a tropical depression lies in Kentucky, roughly 550 miles from the Gulf of Mexico and more than 950 miles away from its initial landfall point! If you wanted a really good drinking game about a week ago, I would have kindly suggested that you drank every time the words “brown ocean” were tweeted by scientists. This philosophy is the thought that saturated ground could be somewhat favorable for development or at least uninhibitive to tropical cyclones. The theory says that saturated ground and provide both a heat and a humidity source that inland tropical cyclones typically lose as they move inland. You can see this theory in play in Tropical Storm Fay (2008) over Florida and Tropical Storm Erin (2007) over Oklahoma. Models did a decent job at pegging the steady nature of the strength of this system through the southern Plains and into the Ohio Valley. There were two distinct pressure drops well inland possibly due to this process. One of the these pressure drops occurred as Bill approached the Red River. The OK Mesonet data is below:

Radar, pressure, and winds from the Oklahoma Mesonet and NWS

Radar, pressure, and winds from the Oklahoma Mesonet and NWS

As Bill moved across the Mississippi River, it became truly just a rainmaker for most. It not only helped relieve drought in the southern Plains, whether they needed it or not, Bill also helped relieve drought in the southern Midwest. Bill had at least one more trick up its sleeve as it crossed the country. Along with the flood warnings that followed Bill to the east coast, there was enough energy in front of Bill to re-energize the characteristic stronger eastern semi-circle. Although not entirely due to Bill, the mid-Atlantic and mid-Appalachians saw more than 250 severe wind reports on June 20th into the morning of the 21st. These reports, below in verification of the SPC outlook, also saw a few reports of tornadoes and hail.

SPC 12z Outlook and verification on June 20th, 2015

SPC 12z Outlook and verification on June 20th, 2015

You can see the eastern side of the remnants of Bill explode as it approaches the east coast and then decay as it moves into the northern Atlantic on the below NASA satellite imagery. Baltimore, Washington, and Richmond all had severe weather warnings of one kind or another. You can also see how clear the rest of the tropics were (and remain) and how much stronger the Mesoscale Convective System was in comparison to this named system. This loop reminds us that a name is not necessarily a sign of strength, especially during the spring in comparison to the plains severe storms.

Remembering Bill

Just like Erin and Fay, Bill will likely be remembered for being a long tracking rainstorm rather than a 60 mph tropical storm that formed quickly in the Gulf of Mexico. Ana and Bill also drive home the point that it only takes 1 or 2 landfalls to make a season memorable for a certain area, even in an El Niño. These two storms are likely the first time two consecutive tropical cyclones to make landfall in the US since 2008. With five months left in this season, it is important to remember that it only takes one to cause problems. Let’s hope that the third system is a charm and stays out to sea. It’ll likely take a while until the damage toll is realized, at least from flooding alone.

I’ll be watching for our next system. Let me know if I missed anything, or what you would like to see here.

Thanks, Jonathan (@JonathanBelles)

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