Ana Downgraded to a Tropical Depression: National Weather Activity on a Downward Trend, Finally

The long weather weekend that couldn’t decide which season it was in is finally coming to a close. Today alone, we had one of the earliest tropical storm landfalls on record, a blizzard, and in excess of 60 severe weather reports…the last two of these happening in South Dakota alone! A storm that produced an EF-3 in Cisco, TX killed one person, and damage in many parts of the Plains continues to pile up. The one minor piece of good news for both those in the Carolinas and for forecasters is that Ana has been downgraded to a tropical depression and the last advisory from the NHC has been written. Tonight, there is a possibility that the Weather Prediction Center will write summaries for both a blizzard and an ex-tropical storm.

The NWS Watch and Warning map today as edited by Joseph Cooper.

The NWS Watch and Warning map today as edited by Joseph Cooper.

In terms of the lifespan operationally, it is now over. Ana’s subtropical and tropical life lasted just two days, but the forecasts go back at least a week. Drawing back to the Florida Straights and the Bahamas both upper level and surface components came together in near perfect harmony, or at least as good as tropical vibrations go in May. Ana fought with dry air and less than sufficient water temperatures throughout many of those short hours, but just like Olaf in summer, Ana persisted. Ana taught us that sometimes the list of necessary conditions for development came sometimes come with an asterisk.

Radar imagery from Wilmington, NC over the last couple of days. From Brian McNoldy, Univ. of Miami, Rosenstiel School

Radar imagery from Wilmington, NC over the last couple of days. From Brian McNoldy, Univ. of Miami, Rosenstiel School

When Ana made landfall at 6 AM near Myrtle Beach this morning, rainfall totals were in surplus of 4″ in areas surrounding Cape Fear, NC. The heaviest rainfall stayed off shore, but rainfall continues to fall between Wilmington and southern Pamlico Sound. Rainfall amounts of up to 3″ in addition to what has already fallen could fall in eastern North Carolina and SE Virginia overnight into tomorrow. Surf will remain choppy near Eastern North Carolina and the Mid-Atlantic. The combination of Ana’s remaining energy and the energy of the incoming trough will open the door for a short-lived and weak tornado or two in eastern North Carolina and SE Virginia over the next few days.

Luckily no major damage has been reported with Ana. The saving grace seems to have been the cooler waters off the coast of the Carolinas and friction. Minor power outages that were caused by falling limbs are quickly being restored. Flooding and road closures will also be alleviated with time.

From Wikipedia, subject to errors and updates.

From Wikipedia, subject to errors and updates.

Meteorologically, Ana got a pressure that pushed a couple of millibars below 1000 and winds of 60 mph. I would not be surprised to see the final report of Ana slight upgrades in these categories on Saturday. The forecast was well done from the start. Going forward, the trough to the west is expected to pick Ana’s remnants up and accelerate them to the northeast. Ana’s remnant’s will be somewhere east of Boston on Tuesday without impacts there.

Tonight, I’ll leave you not with another Frozen joke, but with a stellar image from Thomas Zimmerman that well summarizes the relationship that we as life here on this green planet have with forces of nature.

050915 Grinnell, KS

Grinnell, KS on May 9th, 2015

With at least this weather system calming down, I have to recognize the forecasters of the NWS that are putting up with these messy systems even when their own homes have been damaged by hail and floods this past weekend. Hopefully there will be more fair conditions for everyone this week.

Until next time, stay safe! Hopefully the rest of the season is this forgiving…

–Jonathan, @JonathanBelles

 

Tropical Storm Ana is Beginning to Bring Rain and Wind to the Carolina Coast

Tropical storm Ana continues to outperform as a May tropical storm. Winds of 40-50 mph are starting to bear down on the Carolina coast near Cape Fear and in the coastal waters. Radar imagery this afternoon and evening continues to show winds at 2-4 kft in the 60-70 mph range, but it is doubtful that they will reach the surface. Light to moderate rain has been intermittent this Mother’s Day eve, but unfortunately the worst is to come. The Hurricane Hunters are flying tonight in what looks to be a very healthy storm. The impacts of dry air have lessened, and the cooler air aloft seems to be allowing Ana to hold steady, even allowing an eye-like feature to poke through on IR satellite this afternoon.

Reflectivity and Velocity from KLTX as of 7:45 PM ET. Blue values on velocity, right, are suggestive of winds in the 60 mph range (+/- 5 mph)

Reflectivity and Velocity from KLTX as of 7:45 PM ET. Blue values on velocity, right, are suggestive of winds in the 60 mph range (+/- 5 mph)

Latest Information (8 PM ET)

Maximum sustained winds: 50 kt/60 mph (NHC)
Minimum central pressure: 1001 mb (3 mb increase from yesterday)
Location: 33.1N 78.2W/NW at 3 mph (Recon Fix)
**A Tropical Storm Warning is in effect for South Santee River, SC to Cape Lookout, NC

Synopsis: 

An eye-like feature or some local subsidence has appeared as an empty gyre region on Wilmington’s radar and as an intermittent warm spot throughout today on infrared imagery. Dry air seems to have taken a back seat to shear this afternoon. It was clear that Ana’s core was tilted toward the east or northeast with height this afternoon likely due to shear, but new convection seems to have uprighted the system. Microwave imagery continues to show that there is some mismatch between the low level and mid level centers. Shear clocked in at 20 kts on the 18Z SHIPS, and SST’s came in at around 74°F and cooling. Both of these are not necessarily favorable for development. It has to be reasoned that the upper level temperatures have to be cooler than average in order to get the needed temperature contrast between surface and troposphere to produce new convection. I also have to wonder if there are any non-tropical processes still going on at a minor scale. A slow transition back to those processes will occur in 48 hours.

Evening water vapor over Tropical Storm Ana.

Evening water vapor over Tropical Storm Ana.

Impacts:

–Rainfall: 2-4″ of additional rainfall in possible between Myrtle Beach and Pamlico Sound, but much higher totals are possible over the Atlantic and coastal areas. This system is expected to be a slow mover, which means that isolated locations may see significantly higher totals. Satellite estimates show that upwards of 6” has fallen over water in the last 24 hours, and this rainfall rate could move ashore overnight. A flood watch is in effect for coastal areas. The highest rainfall totals will be near the NC/SC borderlands and points northward along the NC coast. Rain will not be persistent until late tonight.
–Wind: Sustained winds of 40 mph or higher are occurring just off shore and are possible in the coastal waters and the Carolinas coast through Sunday evening, with winds gusting to 60 mph near the landfall point along the coast. Winds may be intermittent in nature tonight, becoming more sustained toward daybreak and into the afternoon. Tropical storm force sustained winds will begin in coastal NC/SC near the border soon, extending inland less than 25 miles from Charleston to Jacksonville, NC. Radar indicates winds up to 60 mph at 3,000ft, which could mix down in the form of gusts overnight.
–Rip Currents/Surge: There is a high risk of rip currents this weekend mainly on the northern side of the low pressure system. 4-8 foot waves will accompany these currents with the highest 1/3rd of these waves up to 14 feet. Avoid the beach and the waters through this weekend. Water could rise as much as 2 feet along the Atlantic coastline of North Carolina through Sunday evening. Beach erosion is  an issue due to the longevity of this system.
–Mariners: A tropical storm warning continues through the weekend. Winds to tropical storm force, waves to 8 feet, and otherwise bad conditions are expected. A few gusts could reach 50 kt. Waves may reach 14 feet close to the center of circulation in the worst case scenario.
–Tornadoes: SPC has placed coastal NC south of Cape Hatteras in a marginal risk for tornadoes in the front right quadrant as Ana approaches land tomorrow. The threat of tornadoes and damaging winds extends into northeastern inland SC and inland NC on overnight, and then up to Cape Hatteras and Pamlico Sound tomorrow through Tuesday morning. Any tornadoes will be weak and short-lived.

*Experimental* product from the NHC that shows rainfall over the past 24 hours. The core of 4-6" may make some headway toward the Carolina coast overnight.

*Experimental* product from the NHC that shows rainfall over the past 24 hours. The core of 4-6″ may make some headway toward the Carolina coast overnight.

Forecast: 

It can only be reasoned that Ana will have to weaken as it moves off of the Gulf Stream into the cooler shelf waters. Winds should come down to 40-50 mph before landfall near Myrtle Beach or the NC/SC border tomorrow morning or early afternoon – a track that is pretty well set now. This will NOT lessen the amount of rainfall any one spot will get, but it will lessen impacts from wind and possibly surge from current intensity. You’ll notice below that there is a secondary maximum at 60 hrs (Monday/Tuesday) over the Mid-Atlantic. The trough that is currently causing the moderate risk of severe weather over the plains states will be arriving at the Appalachians by then, and will scoop Ana up and out of the Carolinas by Sunday and the Mid-Atlantic by Tuesday. Winds often increase in these systems as they become non-tropical.

Model intensities through 5 days. Courtesy Tropical Atlantic.

Model intensities through 5 days. Courtesy Tropical Atlantic.

Bottom Line: It’ll be a pretty gross couple of days starting tonight in the Carolinas into early this week along the east coast. Rainfall looks to be the main issue now with some places possibly seeing 4-6″ around North Myrtle Beach and into coastal SE NC. I’ll leave you all with this night-time visible imagery from last night.

Day-Night Band VIIRS imagery from overnight on the 9th of May.

Day-Night Band VIIRS (visible) imagery from overnight on the 9th of May.

If this weather isn’t your sort of thing, and maybe Ana has given you ideas about snowmen, you can head to the Rockies. If you like or fear severe weather instead, you can get that too in the central and southern Plains today and from Chicago to Brownsville over the next couple of days. Plenty to choose from, and plenty to learn from. That’s why I’m here. Have a good night, and wherever you are stay safe! You may also want to join Mark on Hurricane Track as he rides out this storm near Wrightsville Beach, NC @HurricaneTrack on twitter. Pictures and ustream from the coast.

–Jonathan, @JonathanBelles, Updating throughout the evening!

Ana is Transitioning to a Tropical Storm: Rainy Mother’s Weekend on the Beaches Shaping Up

Ana’s subtropical origins are slowly being relinquished. Satellite imagery today has shown that dry air has wrapped all the way around Ana’s core, but seems to have assisted the subtropical cyclone in reorganization. Over the last few hours RGB imagery has shown that the naked center, which was disorganized to begin with, has tucked itself or redeveloped under the convective band that has developed on the eastern semicircle. You can note in the IR imagery below that when that occurred, convective activity shot up. Cloud top temperatures dropped into the mid to upper -50°C’s or -60°C’s.

IR imagery of STS Ana this evening (8 PM ET).

IR imagery of STS Ana this evening (8 PM ET).

Latest Information (9 PM ET)

Maximum sustained winds: 50 kt/60 mph (ATCF, backed up by recon)
Minimum central pressure: 997 or 998 mb (From recon, 7 mb drop from yesterday)
Location: 31.9N 77.3W/Stationary (Recon Fix)
**A Tropical Storm Warning is in effect for South Santee River, SC to Cape Lookout
**A Tropical Storm Watch is in effect for Edisto Beach South Carolina to South of South Santee River

*Note that the Hurricane Hunters have found winds as high as 55 kt/65 mph at FL/SFMR without tapping into the best convection

Synopsis: 

Today was probably a rather boring day on the Carolina coast for those that know there is a storm off the coast with just some light rain and a slightly breezier condition. That is the effect of the dry air that wrapped around the western side of Ana last night into today. Ana is beginning to fight that dry air tonight by reorganizing and using the decently warm waters below. It is also a decent approach to think that environmental temperatures aloft have to colder than typical in order to foster thunderstorms over rather marginal, but decent sea surface temperatures.

Reconnaissance data up until 9:35 PM ET.

Reconnaissance data up until 9:35 PM ET.

Recon this evening has shown some hurricane force winds at flight level, however the highest winds on SFMR in most of this storm are in the 40’s. In the deepest convection, SFMR was found to be in the low 60’s, which supports intensification but not on the large scale. This to me means that there may be some baroclinic/non-tropical processes still in play. This mismatch will likely be reduced in the next 24 hours. These winds will mix down to the surface from the 5000 ft level (Flight Level) with thunderstorms on occasion.

Subtropical Storm Ana from the International Space Station

Subtropical Storm Ana from the International Space Station

Impacts:

–Rainfall: 2-4″ of additional rainfall in possible between Charleston and Virginia Beach, but much higher totals are possible over the Atlantic. This system is expected to be a slow mover, which means that isolated locations may see significantly higher totals. The highest rainfall totals will be near the NC/SC borderlands and points northward along the NC coast. Rain will not be persistent until late tomorrow as dry air still has to work its way out.
–Wind: Sustained winds of 40 mph or higher are possible in the coastal waters and the Carolinas coast through Sunday, with winds gusting to 60 mph near the landfall point. Gusts may be higher if intensification continues. Winds may be intermittent in nature. Tropical storm force sustained winds will begin in coastal NC/SC near the border tomorrow afternoon.
–Rip Currents/Surge: There is a high risk of rip currents this weekend mainly on the northern side of the low pressure system. 6-9 foot waves will accompany these currents with the highest 1/3rd of these waves up to 15 feet. Avoid the beach and the waters through this weekend. Water could rise as much as 2 feet along the Atlantic coastline of North Carolina through Sunday afternoon. Beach erosion will become an issue due to the longevity of this system.
–Mariners: A tropical storm warning continues through the weekend. Winds to tropical storm force, waves to 8 feet, and otherwise bad conditions are expected. A few gusts could reach 50 kt. Waves may reach 15 feet close to the center of circulation in the worst case scenario.
–Tornadoes: SPC has placed coastal NC south of Cape Hatteras in a marginal risk for tornadoes in the front right quadrant as Ana approaches land on this weekend. The threat of tornadoes and damaging winds extends into northeastern inland SC and inland NC on Sunday. Any tornadoes will be weak and short-lived.

Forecast: 

Although I’m not sure if it is a trend or a sudden jump since we did not have recon this afternoon, but I can only think that slow intensification is possible until Ana slips off into the cooler shelf waters closer to land. Shear is expected to increase over the next day, which may negate any help that the cold upper level temps and meager SST’s. Pending this latest jump in intensity, the trend should thus be for a plateau in intensity or minor intensification. Some weakening is forecast as Ana gets into the cooler waters, and then more so as Ana moves ashore. As Ana reacquires, non-tropical characteristics in the mid-Atlantic, it will likely re-intensify to a strength comparable to a tropical storm.

Due to the reason I mentioned above, and the lopsided nature of Ana in terms of convective activity, I think that NHC may delay the call for a tropically natured TC until tomorrow. The cyclone phase diagrams from FSU show that tomorrow will likely be the last day for Ana to become tropical, and I believe that it will transition to a tropical storm tonight or tomorrow. The radius of maximum winds should continue to decrease, which may also assist in slight intensification.

Cyclone Phase diagrams from Florida State University. From the GFS model at 18Z.

Cyclone Phase diagrams from Florida State University. From the GFS model at 18Z. Movement from C (Current) to the bottom right of the image is suggestive of a more tropical system.

In terms of the track forecast, a majority of the models bring the very center of what will be Tropical Storm Ana to the coastline of NC or SC between Myrtle Beach and Wilmington as a moderate tropical storm on Sunday afternoon. Due to the slow motion of this system, tropical storm force winds will move into the borderlands of NC/SC tomorrow afternoon intermittently.  This motion is due to high pressure building in to the Mid-Atlantic tomorrow, which will guide Ana to the NW and slowly accelerate her toward the coast. By late Sunday, the trough that is causing the very messy weather in the plains states will be in place nearing the Appalachians  to escort Ana to the northeast at an even quicker pace.

Bottom Line: 

Ana has at least temporarily undergone an intensification phase that is in part due to the transformation from subtropical to tropical. As Ana sits over the Gulf Stream Current a hundred miles east of the Carolina coast, slight intensification is possible. The track forecast brings tropical storm conditions to the coastal areas of the Carolinas tomorrow afternoon, and conditions will deteriorate there tomorrow and in inland North Carolina and Virginia through Monday. The biggest threats are coastal erosion and heavy rain along the coastline. I would not plan too much outdoor activity this weekend if you are in the Carolinas.

Stay safe, and have a good night. As always, you follow me on twitter @JonathanBelles

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