Another Accumulating snowfall for the Higher Elevations

In less than one week another snowfall accumulating snowfall is in store for the higher elevations of the #518 area. Just like last Saturday night-early Sunday morning's snow, locations AT and Above 1500 feet have the highest chance for see a moderate snow accumulation.

Near the 1500 foot location snowfall amounts will be near 2-3 inches, near 2000 feet, 3-5" of snow are likely and elevations > 3000 feet will likely see 5-7" of snow with a couple of locally higher amounts possible. A WINTER WEATHER ADVISORY is in effect for Thursday 27 Oct 2016 for the Adirondacks and western Catskills. The snow will mix with some sleet and perhaps briefly some freezing rain before changing over to all rain by late Thursday night

Below is a  forecast animation (from the Hi-Res WRF model) showing the expected development of the rain and snow across eastern NY State and western New England.

It looks like Thursday evening's commute home will be when the "worst" of the wintry weather will occur. Be safe if you must travel!

Sayonara Indian Summer, at least for now.....

Some much needed rain will be heading our way. It should start by late Thursday and not taper off until early Sunday. Keep the rain gear and umbrellas handy, as the rainfall will be frequent and widespread versus intermittent and scattered and it will also be locally heavy at times, too. Even though it has been dry, locally heavy rain could lead to some flooding in areas of poor drainage, low spots and urban areas.

Also it will turn much colder, as in BELOW normal cold by late Saturday into Sunday. Rain will probably mix with if not even change to snow over the higher elevations (AOA 1,500 feet) of the northern Adirondacks. It wouldn't surprise me if there were some minor accumulations here!

It will also turn windy over the weekend, winds may gust to 40-50mph across the #518wx from late Saturday right through most of Sunday.

Hurricane Matthew still remains a powerful storm

The latest advisory as of 11 PM EDT has the center of Hurricane Matthew located about 325 miles Southwest of Port  Au Prince, Haiti. It was moving North at 5 mph with maximum winds of 145 mph and a central pressure that is a bit lower now at 943 mb or 27.85". The past 48 + hours have been remarkable in terms of the storm maintaining it's Categiry 4 intensity. Often major hurricanes see fluctuations in intensity but not this storm.

The latest satellite picture shows a well defined eye of about 10 nm in diameter embedded with in a feature called a Central Dense Overcast (CDO), the bright white circular ring around the eye (refer to image below).

Another perspective of the storm's structure is an IR enhanced photo (image below) showing cloud top temperatures. The bright orange color ringing around the the eye of Matthew are cloud top temperatures of -70° C or colder, indicative of very tall/high cloud tops.

The image below is from an ASCAT satellite pass. This satellite can observe wind speed and direction. The wind barbs show a very tightly wrapped cyclonic circulation with very strong winds. The pennants or triangles are for wind speeds of 50 knots, 2 pennants on one wind barb equals 100 knots and the satellite was able to observe winds of this speed.

One of the reasons why Matthew has been able to maintain its intensity is that it is in an area of favorable divergent winds aloft and very low wind shear (image below) as well as being over extremely warm waters, where sea-surface temperatures are in the low to mid 80s.

Hurricane Warnings and Watches along with Tropical Storm Warnings and Watches are posted for Caribbean Islands and the Bahamas:

The official NHC track has Matthew moving in a general north direction. Thus the center  of Matthew will not make landfall on Jamaica and could even just pass to the west of Haiti. However, with tropical systems that move in a northerly direction the worst rainfall (and wind is to the right or east of the center. This means that parts of extreme western Haiti could experience hurricane force winds and will also likely receive very heavy rainfall. where amounts of 15-25 inches are forecast (even east to the southwest parts of the Dominican Republic) and some local amounts to 40 inches could also occur here. Needless to say rainfall totals such as these will likely produce catastrophic flooding and flash flooding. The eye of the storm is expected to make landfall on the east end of Cuba late Tuesday resulting in some slight weakening but even so Matthew is expected to remain a major hurricane as it moves across the central Bahamas during late Tuesday through Wednesday.

And by the end of this week Matthew is expected to be a few hundred miles off the Carolina's coastline. It is something that all of the East Coast states will have to watch, including all of us here in Upstate New York. I'll keep you posted.

Tropical Storm Matthew

The  Tropical-disturbance-in-atlantic-invest.html that I posted on yesterday has become Tropical Storm (TS) Matthew. The satellite loop from CIMSS (below) indicates that TS Matthew continues to slowly organize. The outflow on the north side of the storm is good and is fair to the south. The storm's proximity to the continent of South America will likely mean only a gradual intensification of the storm over the next 24 hours, nonetheless it is expected to become a minimal hurricane.

Upper air winds are favorable for a steady development based on the latest high-level wind analysis from the UW-Madison Tropical Cyclone analysis page:

The area of unfavorable shear (image below) continues to recede westward ahead of Matthew's as the storm travels toward the west  or slightly north of west motion over the next 72 hours.

Thereafter, once it nears 75° W longitude model data is  forecasting Matthew to make a hard (anti-NASCAR) right-turn.

As the spatial separation increases between the storm and the coast of South America, the system is expected to intensify at a slightly faster rate; I think that during the post-72 hour period as the storm turns north there is the potential for it to undergo a period of rapid intensification. But again for now thinking/being conservative here.

At 11 PM Matthew was located approximately about 370 miles/595 kilometers SSE of San Juan, Puerto Rico or about 370 miles ENE of the Island of Curacao. Maximum winds were 65 mph with higher gusts and the storm was moving West at 15 mph.

Tropical Storm Warnings and Watches are posted for some islands in the Lesser Antilles and along the north coast of Venezuela.

Time will tell what, if any, impacts Matthew will have on the U.S. mainland. Already, the internet is abuzz with wanna be meteorologists making unfounded posts of meteorological armageddon based on long range weather models. Make sure what you view online is from a credible source - either from the NWS, NHC or a credible meteorologist! Rest assured, I'll be keeping both eyes on this system.

Tropical Disturbance in Atlantic - Invest 97L

A  tropical disturbance (97L) in the Atlantic Ocean located about 415 miles to the east-southeast of the island of Barbados is showing signs of becoming better organized this afternoon. Hurricane hunters are tasked to do a reconnaissance of it this afternoon.

Based on satellite wind data and minimal surface reports the system doesn't appear to have a closed cyclonic circulation at the moment. Below is a visible satellite picture of the system on the left and the satellite winds on the right.

(Visible Satellite Imagery oif 97L)

(High Level Wind Analysis over and around 97L)

(Current Divergence Analysis)

Of interest is the wind field in and around the disturbance. The wind flow is anticyclonic or diverging. Divergence increases upward motion of the air (image to right) and causes a lowering of the atmospheric pressure at the surface,

 In addition to divergence, tropical systems need warm ocean waters Sea Surface Temperatures/SST) of at least 26°C/78°F for their development or intensification. The disturbance is currently over SSTs of 28°C to 30°C (image below).

(Sea Surface Temperature analysis)

The other favorable element for potential development is for little wind shear aloft. Strong shear (of 20kts or greater) disrupts a tropical system's circulation and structure. Shear can inhibit development or even weaken a tropical system. Based on the latest wind shear analysis (image below), the shear is favorable (i.e., LOW) over 97L., but to its west the shear is strong (unfavorable).

(Current Wind shear)

However many of the forecast models are forecasting this shear to relax considerably over the next two days, that is these forecast aids are indicating little shear as 97L moves into the Eastern Caribbean Sea.

The forecast model spaghetti plots for 97L are clustered around a W to WNW heading through the end of the week. Of these models that forecast intensity of tropical systems, most if not all are forecasting 97L to become at least a tropical storm. If this did occur then 97L would be christened "Matthew".

(Forecast model ensemble tracks for 97L)

Per the NHC, "Interests in the Windward and southern Leeward Islands, Bonaire,Curacao, Aruba, and along the northern coast of South America should monitor the progress of this disturbance. Regardless of whether the system is a tropical wave or tropical cyclone, heavy rains and tropical-storm-force winds in squalls are expected to spread over the Windward Islands and portions of the southern Leeward Islands, beginning tonight and continuing through Wednesday."

Credits: First 5 images from University of Wisconsin CIMSS Tropical System web site: CIMSS

Prolonged Wet Spell Still Likely

Much needed rain fall occurred across parts of the Northeast States on Wednesday morning helping to begin to ease the dry and drought conditions across parts of the region. Nonetheless a severe drought continues for most of the Northeast. Areas of west-central and western New York State as well as a good portion of Southern New England remain in moderate or severe drought as shown in the image below.

.

From the US Drought monitoring service here is the discussion regarding the Northeast's drought:

"Moderate to heavy rains, locally exceeding 5 inches, fell on areas from southwestern New England southward and eastward into the mid-Atlantic and through the central Appalachians. These rains removed dryness and drought from most of West Virginia and in the mid-Atlantic south of the Mason-Dixon line, but only scattered improvement was noted elsewhere. In eastern and northern New England, where only light rain fell, severe drought expanded through most of Massachusetts, and moderate drought covered the rest of southern New England. Rainfall deficits for the past 90 days range from 4 to 9 inches in much of this region. In addition, long-term rainfall shortages remain entrenched, with accumulated shortfalls over the past 2 years of 12 to 24 inches observed from central New England southward into northeastern Pennsylvania. Temperatures averaged a few degrees above normal this past week, exacerbating conditions."

However there is going to be a definite pattern change as it relates to our dearth of rainfall. As I mentioned in my update A Drippy Looking Long Range, the next 7 days upcoming will feature frequent bouts of  showery rains and thunderstorms with any shower or storm capable of producing torrential rain. Even though it has been dry and the rain will be absorbed by the ground, there is the chance that too much rain could fall in a short time period (like 2 hours or less) resulting in the threat for flash flooding. Definitely something to keep an eye on.  

Weather data is coming into agreement on both what periods during the next 7 days will be the rainiest and how much rainfall is possible.  For Eastern NY State and Western New England (our neck of the woods) the best chance for widespread rain  will be from Thursday into next Monday. The best chance for getting soaked will be during the afternoon hours right up through early night (10 PM or so). The exception to this will be this Saturday August 13th when the rain could start earlier and will probably continue well into the early morning hours of Sunday before it diminishes from NW to SE as Sunday moves on. This same weather data continues to indicate that precipitable water values over the next 5 days will be  near +3 standard deviations (SD) above  normal with values rising to near +4 SD on Saturday. These high deviations above normal strongly favor heavy rain. And once again several features will come together in time and place to efficiently make the heavy rain happen..

Here is the 7 DAY TOTAL AMOUNT of rain expected. (Forecast is from the Weather Prediction Center) It is for the 168 hour period from 8 AM Wed 10 Aug through next Wednesday, 8 AM 17 August:

The forecast map indicates a widespread 1.5-2 inch rain fall for us with more than a few locations getting 3 to even locally near 4". Keep in mind this the total expected rainfall for the next 7 days . BUT as for our region goes, I think that most of this heavy rain will occur in the Friday through Sunday morning period, with Saturday seeing the most rain.

A Drippy Looking Long Range

Long range forecast data as well as teleconnections and analogs are pointing to some potentially interesting weather for the Northeast states during the 10th-14th of August. We could be in for a prolonged period of wet and unsettled weather. Some of the unsettled weather could be in the form of possible strong thunderstorms. But like most severe weather threats much will depend on S.L.I.M factors, that is (wind) Shear, Lift, Instability and Moisture and how these ingredients come together in both time and place.

Severe weather possibility aside,  forecast data is indicating some high (octane) moisture swirling our way from late Wednesday into the upcoming weekend. Forecast data is indicating higher than normal precipitable water (PW) content over the Northeast US during this time period.

What is precipitable water (PW)?

PW is defined as the depth of water that would accumulate on the ground if all the moisture in the air above you fell as rain. So if PW in the column of air above has a value of let's say 1 or 2 inches then under prefect conditions you would see one or two inches of rain. PW values vary by day and season. By season there are "normal" PW values. So by comparing either the actual day's PW value or forecast value, one can assess the potential for significant precipitation.

Forecast PW departures from normal for the period Aug 10th-14th

The ensemble forecast  average is indicated on the charts above. This forecast value is then "compared" to normal PW values for the given dates. The comparison yields how many standard deviations (SD) ABOVE or BELOW normal the forecast PW values are. The greater the number of deviations the more anomalous the parameter is. The above data is taken from the GEFS forecast data sets and indicates that PW values will be near 2-3 SD above normal for much of this time, with SD increasing to +3 to +4 SD above normal on Saturday. These above normal SD values of precipitable water would tend to favor the possibility of a lot of rain, locally heavy on Wednesday, and then again from later Thursday through the first half of next Sunday the 14th.

To "wring" or condense the moisture out of the air the next weekend we'll need a lifting mechanism. . it looks like a stronger than normal (for mid-August)  low pressure system (by -2 to -3 SD; image above) will be moving across the Eastern States and provide the lift needed.

So for now the end of this week and next weekend looks like a prolonged period of wet weather is heading our way. We do need the rain, but there is the chance that some of us may wind up with too much rain in too short a period of time.

As of now forecast data sources indicate  locally heavy rainfall is possible on Wednesday with a better threat for more substantial widespread rainfall next Friday through Sunday. For now conservatively a widespread 1.5-2.5 inches could fall during this period but as always there could be locally higher amounts.

How high is the question. Small scale/mesoscale features like  thunderstorms: where do they form and how do they move could be factors in enhancing local rain fall amounts. Will these storms repeatedly form or move over the same locations?  Other features like outflow boundaries (which are caused by convection) and their interactions with other large and small scale weather features COULD lead to some local enhanced heavy rain amounts, too. This in turn could perhaps cause some local flooding issues.  The "small" and mesoscale systems are near impossible to predict days ahead but based on past experience, I think that they will show up as we get closer to the end of this week .

I'll be watching, as should you by keeping up on the latest weather forecasts.

Weather Discussion for Saturday 6 August 2016

A cold front has stalled just to the northwest of us but it will still start to move toward the southeast during this afternoon. With the air heating up and the front moving through the region during this afternoon scattered showers and a few storms are possible. Greatest instability is to the S by SE of Albany with better shear and lift to the north. For now SPC has SE NY and Southern New England (mainly south of the MASS Pike) as having the better chance for severe storms.

This better chance is based on the assumption that this area will be "heating" for a longer time frame. BUT looking at the image below you can see that skies are mostly cloudy to the south and southeast of Albany, with a few breaks. The most sunshine and warming is occurring to the north and northwest but instability in this area is not too strong.

So I have to say that it's a low confidence forecast on today's severe threat. While I am not thinking that there is going to be a widespread severe threat, I feel that most of the #518wx area does have a chance for a strong or severe storm. Storms will be widely scattered if they do occur. For the weather geeks, the morning upper air sounding for Albany (modified for expected conditions at 1 PM this afternoon) is below. Analysis of this sounding shows moderate to strong CAPE (Convective Available Potential Energy) but the profile of this CAPE is somewhat "skinny". Instability indices are mostly weak ( one or two moderate); these mostly weak indices are probably due to a weak temperature lapse rate (change of temperature with height) between about 5 thousand feet and 12 thousand feet above the ground.

(8 AM EDT 6 Aug 2016  RAOB for Albany NY. Modified for expected afternoon conditions)

IF SEVERE storms happen, the main threat: strong wind gusts (wet downbursts) of 50-60 mph and very heavy rainfall. The chance for large hail is LOW. Best chance for storms/showers (40% probability) is between 1PM and 6PM today. Once again activity will be scattered, so not all of us will get wet. Also note that some storms could produce a quick 1" to 1.5" of rain in a short time, with an isolated 2-2.5 inches even a possibility. This heavy rainfall could cause local flooding in areas of poor drainage, even isolated flash flooding, as well as ponding fo water on the roads.

Earl rather low central pressure but still not a hurricane

Usually when tropical systems in the Atlantic basin have a central pressure around  992 millibars (29.29" Hg) the maximum wind speed is at least minimal hurricane force. Earl's latest central pressure has been just below 992 mbs for the past 12-15 hours and the wind still remain in the 65-70 mph range.

Earl is still expected to become a minimal (Category 1) hurricane today. However, it is interesting to note that it has yet to become one.Two possible reasons why it has not done so (and MAY NOT do so) are: 1) It now has the Isthmus of Central America to its south. This could be disrupting inflow into the lower level of the storm along with "relatively" drier air being drawn into the storm's circulation from off the isthmus (as depicted in image below).

2) Dropsonde data (plot of temperature and dew point from a specified height above ground downward to the surface) from recon aircraft indicates dry air between about the 900 millibar surface up to approximately 760 millibars (purple circle on image below).

Dropsonde plot courtesy of: http://aircraft.myfoxhurricane.com/

On the favorable side for intensification are very warm SST (Sea Surface Temperatures) and little shear along with a small area of high pressure aloft over the cyclone providing some favorable outflow.

Tropical Storm EARL

 Reconnaissance aircraft reports indicate that the strong tropical disturbance moving rapidly west across the Caribbean Sea has developed a closed (low pressure) circulation. In addition strongest observed winds are 45 mph or tropical storm intensity thus the system is given the name EARL, the fifth named tropical cyclone of 2016 for the Atlantic Basin

EARL will make landfall on Belize late Wednesday night (3 Aug) or early morning of the 4th. It will weaken to below tropical storm intensity. By Friday it is forecast to move back over the warm waters across the Bay of Campeche, where some re-strengthening is possible before it makes a second landfall on Mexico's east coast.

In addition to strong tropical storm force winds (perhaps even localized hurricane force wind gusts), EARL will also produce storm surge flooding of 2 to 4 feet along the Belize coast at and to the north of where the center makes landfall.

EARL will also likely be a prolific rainmaker. An additional 2-4 inches of rain is expected across Jamaica. Total rainfall accumulations of 8-12 inches are forecast for Belize, Honduras, Guatemala and the Yucatan Peninsula with some 16 inch amounts possible. These rains could result in life-threatening flash floods and mud slides.

Hello Earl?

Earlier today, I posted ( Atlantic Tropics) about a tropical disturbance (97L)  moving quickly across the Caribbean Sea. Since then based on satellite and synoptic data the system has shown signs of much better organization.


The satellite "signature" itself is quite impressive. The system is taking on a much more circular appearance almost like that of a buzzsaw blade.















This is a sign that indicates that the system is developing outflow. Here is a schematic diagram of the air flow in a tropical cyclone's circulation

Image from: (From NOAA, Hurricane, Washington, DC: Superintendent of Documents, 1977)

Outflow is like a chimney, it ventilates the storm:  air currents move in at surface toward the center of the system, where they converge and rise up. As the air rises the moisture in it condenses releasing latent heat which lowers the air pressure. If this rising air wasn't ventilated from the top of the storm, the rising air would eventually cool and begin to sink. But with an outflow mechanism higher up over the storm this rising air is "removed" and allows the system to develop. The better the outflow aloft the greater the chance for the system to intensify and develop. There is a parodox of tropical system's and their intensification: the more air that is removed from the system aloft, the better the chance for the system to strengthen.

Based on the past few hours of satellite imagery I would not be surprised if 97L were at least a tropical depression come Monday. Time will tell. As of now the NHC is planning a possible aircraft reconnaissance mission for Tuesday afternoon but if recent satellite imagery continues to show better organization I wouldn't be surprised if an invest of it occurred sooner.

Atlantic Tropics

Two tropical disturbances have been working their way across the Atlantic Ocean during the past few days. One out over the far Eastern Atlantic, a couple of hundred miles to the west-southwest of the Cape Verde Islands remains poorly organized and is not expected to develop much as it continues its westward trek over the Atlantic, moving into a hostile environment of strong wind shear and dry air.

On the other hand, a strong tropical disturbance dubbed 97L, is zipping quickly west across the Caribbean Sea.

Satellite imagery of tropical disturbance 97L

While surface data indicates no "closed" circulation  center (of low pressure) with this feature at the present time, the associated area of convection is increasing in both coverage and strength. The fast forward motion of the system is currently a detriment to its development but the forward speed is expected to decrease over the next 48 hours.

As 97L moves into the Western Caribbean Sea (west of 72°W longitude) by late Tuesday (2 Aug 2016), it will begin to move into an area that from a statistical climatology perspective is very favorable for tropical systems to intensify.

Also from a climatology perspective, systems that enter the Caribbean Sea near or south of approximately 15° N latitude on a general westerly heading (both of which 97L has done), tend to "keep" this heading. Forecast model tracks support the "climatology motion", with  97L likely passing close to or more likely to the south of Jamaica.

Forecast model tracks for 97L

As for the models that predict intensity, most show 97L to become a depression once it moves west of longitude 72° W, a few indicate it becoming a tropical storm and a couple have it intensifying into a hurricane.

Very warm Sea Surface Temperatures (SSTs) of near 80° F or warmer and the forecast of favorable

environmental conditions: very moist air and little wind shear would likely favor intensification of this system into a tropical storm. If this were to happen it would be christened with the name EARL.

Thursday 14 July 2016 Severe Weather Discussion

GEEK ALERT..A TECHNICAL DISCUSSION. I JUST WANT TO "SHOW" FOLKS WHAT GOES INTO BOTH THE CREATION OF AND PREDICTION OF SEVERE WEATHER.

I hope you find it interesting.

SATRAD AND TEMPS FOR NY AND NEW ENGLAND

Map of satellite/radar/temperatures  (MAP ABOVE) Indicates that the low clouds of last night and early this morning are beginning to thin or dissipate. Where this occurs sunshine breaks out and the air is quickly warming with temperatures in the low and mid 80s. The more sun, the more the air warms and the more UNSTABLE the atmosphere becomes.

Below is the “sounding” from this morning’s balloon launch from Albany, NY. A sounding or rawindsonde is snapshot of weather conditions aloft over Albany. It’s a measurement of temperatures (red line) and moisture (green line) and wind speeds and directions (wind barbs on right side of diagram) – all this data is plotted on a diagram with the vertical axis being height above the ground and the horizontal axis being temperature. This data is very useful in many areas of local weather forecasting including convection and in gauging the possible intensity of it.

14 JULY 2016 12Z/8AM EDT SOUNDING FOR ALBANY NY

The sounding has been “modified” by “warming” it to this afternoon’s expected maximum temperature (and the expected dew point at that time). The pink area is the indication of the expected instability this afternoon, it is the Convective Available Potential Energy or CAPE. The higher the value of the cape the more unstable the atmosphere. another cape parameter is the downdraft cape or DCAPE. The higher this value the greater potential for strong downdraft/microburst winds. Other data is also calculated from the sounding including other storm motion (direction and speed), as well as, instability indices as well potential rainfall that could occur.

Looking at the modified sounding, if the atmosphere warms enough and the high CAPE values are reached then severe thunderstorms will likely occur. The high DCAPE values of > 1000 j/kg would favor strong winds. The mode of convection, (that is either supercell, clusters, pulse or lines) would likely be in the form of storm clusters or line segments based on the the BRN parameter or Bulk Richardson Number, as well as a hodograph which is a wind speed and direction analysis of the winds aloft. Below is the expected storm intensity analysis and hodograph.

FORECAST STORM MODE

STORM STRENGTH

HODOGRAPH/HODOGRAM FOR ALBANY NY FROM 8AM EDT 14 JULY BALLOON LAUNCH

A “long and nearly straight” hodograph like the one above, is supportive of cluster and/or linear convection.

In addition the storm motion from SW to NE at 15-25 mph could favor convective cells moving over the same area; this is called training. combine the possibility of l for training cells along with relatively slow storm motion and the higher than normal moisture content of the air over the region today,  very heavy rainfall could occur with today’s storms. The risk for local flooding is possible in areas of poor drainage, perhaps even flash flooding; as well as, ponding of water on roads. There is the potential for a quick 1.5-2.5 inches of rain in a very short time in any storm; maximum rainfall potential could exceed 3”, especially in slower moving cells or if training occurs.

So there you have it, how this weatherman prepares a severe weather forecast.

Possible Severe Weather for the Central US Next Days

Severe thunderstorms with large hail, damaging winds and tornadoes are quite likely across the Central U.S. today through tonight.

A severe weather outbreak is possible for the Central US today through tonightt. There are still some uncertainties as to its extent. However, if various weather features that aid in the development of severe thunderstorms, namely: Shear, Lift, Instability and Moisture [SLIM], come together in time and place, then very large and destructive hail (near or larger than softball size, i.e., > 3" in diameter), damaging wind gusts and strong, possible long-track tornadoes,could occur across the central US.

The greatest tornado threat probabilities are from south central Nebraska, south across Kansas, Oklahoma into extreme north Texas. Major metro areas included in this zone: Grand Island and Hastings in Nebraska; Salina, Wichita and Emporia, Kansas; Oklahoma City, Norman and Edmond, Oklahoma.

Another wave of severe weather is also possible across the Southern Plains east to the Lower Mississippi Valley this Thursday through Saturday.

An unsettled Saint Patrick's Day

Cold air aloft associated with an upper-air disturbance will result in scattered showers and some thunderstorms this afternoon. Storms could produce pea-sized hail and brief gusty winds. Any shower or storm could also be accompanied by brief downpours.

A hui hou to Pali

While Atlantic Hurricane Alex has formed this morning over the Northeast Atlantic, former Central Pacific Hurricane Pali is in a rapid weakening phase.

Pali initially formed on 31 December 2015, as a tropical depression about 1850 miles to the SW of Honolulu. Pali moved toward the NW and on the evening of January 7th (Local Hawaii time) became a tropical storm with winds of 45 mph while located about 800 miles SW of Honolulu. Thereafter Pali took a meandering slow track toward the west and then southwest and south southeast over the following 4 days. Gradually the TS organized and intensified into a Hurricane by late afternoon on the 11th.

Pali remained  hurricane and intensified to a Category 2 hurricane on the 12th. Thru the 13th Pali continue to meander SOUTH towards the equator. Its position was now within 3 degrees latitude north of the equator! Late on the 13th the combination of decreasing latitude (Pali was nearing the equator) and strong SW wind shear aloft cause a rapid weakening of the storm.

Today Pali is now a tropical depression near 2.5°N and 173.0°W. Pali is rapidly weakening and forecast to dissipate during the next 24 hours.

Here is a link    The Life of Hurricane Pali  to a movie on my YouTube channel of Pali's track from inception to its current demise.

From Byers and Riehl, Tropical cyclone characteristics are as follows:

1.  they have a greater chance to farm during the summer and fall seasons in either hemisphere.
2. they form over the warmer waters of subtropical and tropical ocean basins, (Usually with ocean temperatures of 26°C or >)
3. they have no warm or cold fronts associated with them.
4. pressure and other properties (winds, rain) tend to be distributed symmetrically
5. they are seldom observed within 5­° of latitude of the equator, This is because the Coriolis force is important in their development.
   
   What is the Coriolis force? It is an artifact of the earth's rotation. Basically "things" in motion on the surface of the earth experience a deflection of their motion due to the earth's rotation. In the Northern Hemisphere this deflection is to the right of the object's apparent motion. (In the Southern Hemisphere the deflection is to the left.) For a very good and brief explanation on Coriolis check out this link: What is the Coriolis Force ?

What do you know? Alex is a Hurricane !

Morning satellite pictures (Fig. 1) indicate that Alex has intensified and developed an eye and has now been classified as a hurricane in the far northeast Atlantic Ocean.

(Fig 1.) Visible satellite imagery of hurricane Alex

The Azores Meteorological Service has issued a Hurricane Warning for the islands of Faial, Pico, Sao Jorge, Graciosa, and Terceira in the central Azores, and a Tropical Storm Warning for the islands of Sao Miguel and Santa Maria in the eastern Azores.

Alex is forecast to move across the Central Azores with increasing winds expected to begin to affect the islands by late tonight. Here is the past track and forecast track for Alex is shown below in Fig. 2

(Fig. 2) Alex ' past and forecast track

After passing north of the Azore on Friday Alex is forecast to curl towrad the NNW or NW and merge with a large extratropical low south of Greenland over the weekend.

According to the NHC Alex is the first hurricane to form in the month of January since 1938, and the first hurricane to occur in this month since Alice of 1955.

Out of Season Subtropical Storm in the Atlantic

The Atlantic Ocean has its first named (sub)tropical cyclone of the year. Alex has formed over the far eastern subtropical waters of the Atlantic Ocean. Last week on the 7th of January the National Hurricane Center (NHC) issued a special Tropical Weather Outlook (TWO), highlighting that an intense extratropical storm could acquire subtropical or tropical features within a week or so as it moved over the warmer waters of the subtropical eastern Atlantic, Ocean.

NHC TWO from Jan 7 2016

Quick Discourse on extratropical, tropical and subtropical lows

EXTRATROPICAL (XT) LOWS develop when potential energy is released due to warm and cold air masses interacting with each other. (Meteorologists call this baroclinicity). XT lows have fronts within their circulation (cold fronts/warm fronts). Winds can be light or very strong. In the more intense XT lows winds can be at or above hurricane force. In addition, the pattern of wind and precipitation with respect to the center of the low can be asymmetrical, that is not necessarily concentrated near the center of the storm. Lastly the core of the storm, especially aloft, exhibits cold temperatures. XT lows can form over land or over the ocean. They also tend to form in mid or high latitudes.

TROPICAL CYCLONES (TC) form over warm ocean waters with a water temperature of 25C-26C or higher. They develop over the subtropical and tropical oceans of the world mostly during the summer and fall months.Tropical cyclones are warm core systems. The energy that allows them to intensify is the latent heat that is released when moisture in the air condenses.  TCs have NO frontal features. Temperatures warm steadily as one gets to the center of the TC. Wind and precipitation tend to be symmetrical with respect to the storm; the most intense rain and wind are near the center. (If the TC becomes a hurricane then center or EYE is often dominated by light or even calm winds and minimal cloud cover and rain).

SUBTROPICAL CYCLONES (STC) are more or less hybrid systems. They often form in one of two ways. One is when an upper air storm with cold air aloft moves over warm SSTs. Cold air over warmth is unstable and thus thunderstorms and cloud formation increases.These type of ST lows tend to be rather large in circulation with a broad area of light winds and cloudy skies in the center. The strongest winds tend to be well removed from the center along with the more intense precipitation.

The second way a ST low can form is when an XT low moves over warm SSTs  (in this case as cool as 19C-24C).  and thunderstorms increase near the center of the low. The system then "warms" and begins to lose its frontal features. These types of ST lows tend to be relatively small in size.usually no more than 300 miles in diameter and some have had diameters as small as 100 miles across (midget cyclones).

If an STC moves over SSTs of 25-26C or greater it can develop a warm core and in turn  become completely warm core or tropical.

About Subtropical Storm Alex

Our newest subtropical storm (STS) Alex has evolved and developed from the latter scenario. On January 6 and 7 2016 and intense XT storm developed between the Bahamas and Bermuda. For the next 5 days it tracked east-northeast across the central subtropical Atlantic Ocean.

Track of Low that became Subtropical Storm Alex

 In time it began to move over marginal warm SSTs and started to lose its XT features and fronts. The SST map below from Environment Canada shows the water temperatures along the track of the low and the current location of  STS Alex. SSTs are 22-24C along and beneath the storm.

Sea Surface Temperatures across the North Atlantic and in the vicinity of STS Alex

STS Alex is forecast to gradually turn NE then N-NNW over the next few days. It will be moving over colder water temperatures so transitioning to warm core or tropical is not expected.

Official NHC track for STS Alex

 However, a surge of very cold air over Eastern North America will move out across the Atlantic and interact with Alex. Once again baroclinic elements will come together and Alex will once again intensify as rejuvenated extratropical storm impacting the shipping lanes of the North Atlantic.

Below is an infrared satellite of Alex over the Eastern Atlantic. Sat pic from Environment Canada

Satellite picture of STS Alex

From the NHC's forecast storm discussion from 5 PM AST 13 Jan: Alex is the first tropical or subtropical storm to form in January since an unnamed system did so in 1978, and is only the fourth known to form in thismonth in the historical record that begins in 1851.

Fascinating! Tomorrow I'll talk more about Alex and on Hurricane Pali in the Central Pacific, far far to the southwest of Hawaii, As a matter of fact Pali is closer to the equator than it is to Hawaii.

January 10, 2016 Mild, Wet and Wild Weather Day....

Wild weather day up here across Upstate New York :

  Record warmth: High of 55° Albany and 65° in Poughkeepsie both record high temperatures for this date

Selected high temperatures for Jan 10th 2016

There was a rapidly NNE moving squall line between 1-4 PM that impacted eastern NY State and Western New England  with thunderstorms producing wind gusts of  35-50 mph in places and some small hail too

Also had a plethora of rainbow reports and pictures, too. Here are 3 of the many pictures

Tom Cowin/Troy, NY

Gwen Ivins/Location Unknown

David Wood/Troy, NY

By morning we'll be be 20-25 across most of the region. Lake effect snow showers already over the NW portions of the Adirondacks and they'll be spreading east and south through the night and Monday. Hope you enjoyed today's very brief January thaw!