Caribbean Wave Poised to Move into Gulf

Tropical Depression One failed to become Tropical Storm Ana earlier this year; however a tropical wave in the Western Caribbean Sea now appears to have the potential to become TD 2 and possibly even TS Ana. The tropical low has been spinning of the coast of Central America, and has developed a large area of thunderstorms over the past 24 hours. The National Hurricane Center has recently given the system a medium (30-50%) chance of developing into a tropical cyclone in the next 48 hours. The wave is expected to bring heavy rains over the Yucatan Peninsula as it moves to the northwest and crosses over into the Southern Gulf of Mexico. Much to the chagrin of the residents of the Gulf Coast, sea surface temperatures (SSTs) in the gulf are in the mid 80s, and conditions are expected to be somewhat favorable for development. If the wave can survive as it crosses the Yucatan, we could be looking at Tropical Storm Ana by the beginning of next week.

Update (6/27/09, 11:53 AM): The tropical wave still does not have a well defined circulation and has lost some of its thunderstorms. Therefore, as the NHC predicted, it is very unlikely that this storm will be named before moving over the Yucatan.

Update (6/28/09, 3:22 PM): The NHC has given this system a low (less than a 30%) chance of developing into a tropical cyclone over the next 48 hours. It remains very disorganized and has lost a bit of thunderstorm of activity. However, it may strengthen as it emerges over the warm waters of the Gulf of Mexico.

Update (6/29/2009, 11:09 AM): The system has lost all of its thunderstorm activity and is no longer expected to develop into a tropical cyclone.

Sea of Tranquility

No, this title does not reference the famous landing site of Apollo 11; instead that title could be used to describe the tropical Atlantic Ocean since the opening of Hurricane Season 2009, on June 1st. The National Hurricane Center has not had much of a chance to issue their slew of new and experimental products. In fact, my least favorite phrase has found its way into the Tropical Weather Outlook almost on a daily basis. "TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS." Does this mean that we are in for that average season that NOAA predicted? Does this mean that the eastern seaboard of the United States can finally take a deep breath this summer? Not quite. Here are some examples of some significant hurricane seasons within the past 20 years that started off slowly out of the gate.

1992 Hurricane Season
This season wasn't exactly the most active season on record. In fact only seven named storms and four hurricanes formed that year. However, it only takes one storm to make an impact. The first named storm of that year didn't form until August 16, but it made its presence felt. A tropical wave emerged from the Eastern Atlantic and became a little tropical storm that you might of heard of, Andrew. That little storm became a powerful Category 5 storm that slammed into Florida while becoming the costliest hurricane in US history. Katrina in 2005, has since past Andrew in that category. Nonetheless, Andrew proved that a quiet first two months does not correlate to a quiet season for the United States.

1998 Hurricane Season
Coming off of a record setting El Nino event, the first few months of the 1998 season were anomalously quiet. In fact, the first hurricane of the season, Bonnie, did not form until late August. However, unlike the 1992 season, this season evolved into one of the most active seasons of the decade. Storms such as the aforementioned Bonnie, Georges, and Mitch devastated the Atlantic Basin. Mitch in particular grew to a powerful category five storm that devastated Central America with its torrential rains. Up to 75 inches of rain fell into mountainous regions of Honduras and over 10,000 people were left dead in Mitch's wake.

Now, does this mean we are in for the same fate as those in Florida in 1992 and Central America in 1998? Absolutely not. In fact there is a good chance that we made indeed have only an average season this year. Just remember the peak of the Atlantic Hurricane Season is still a few months away, and as the great Yankee catcher Yogi Berra once said, "It's not over until it's over."

NOAA's 2009 Hurricane Season Outlook

Last week, I was fortunate enough to be working at the National Weather Service when we were briefed on NOAA's season predictions. The Tropical Prediction Center is calling for a near average season this year with only 9-14 named storms and 4-7 hurricanes.

As I mentioned, I was fortunate to get a chance to listen to some of the scientists who made these predictions explain their outlook. They showed us that the Atlantic is indeed cooler than average for this time of year. Additionally, they explained that we are moving into a shift towards an El Nino pattern. During an El Nino year, there tends unfavorable conditions for tropical cyclone development due to an increase in the amount of wind shear across the Atlantic basin

However, right now we are in an ENSO-neutral pattern which definitely creates some uncertainty because we don't know exactly when the less favorable conditons will set in. However, El Nino is far from the only factor that affects these natural phenomina. Through my undergraduate research, I have learned that the NAO, the Gulf of Mexico's loop current, and even the amount of dust that blows off of the African coast can affect how many storms form in any given year. Therefore, it would not be unheard of to see more or even less activity this year.

If I had to make a prediciton, I would aim a few storms higher than the NHC going with 12-17 named storms. I leave you with this final note: The last time the atlantic tropical cyclone count was in the single digits was way back in 1997, when a record setting El Nino pattern was in place.

Happy hurricane hunting to all of my fellow tropical nuts, and most of all stay safe everyone!

TD One Kicks Off the Season Early

At 11AM EDT, or three days and thirteen hours before the official beginning of the 2009 Atlantic Hurricane Season, the National Hurricane Center issued a public advisory on its first storm of the season. Tropical Depression One formed from a small low pressure system that had been spinning over the Gulf Stream for the past few days. Yesterday, the NHC did not expect this system to develop, but convection arose around the circulation low pressure system last night and early this morning. TD One is expected to become Tropical Storm Ana before it becomes extratropical over the cold waters of the N. Atlantic. Fortunately, TD One is not expect to impact any land masses as it moves NE away from the United States.

Update (6/29/09 6:30 PM): The NHC issued its final advisory on TD One which has lost its tropical characteristics over the cold waters of the northern Atlantic today. It seems like we are just going to have to wait until the official start of the season before we see Ana form. I'll try my best to keep posting whenever there is a storm in the Atlantic this season.

(satellite image courtesy of NOAA and the National Hurricane Center)

Collegian Discourages Volunteer Organization

This letter is in response to the Wednesday, March 4 critique of the Campus Weather Service’s Weather Page.

The Daily Collegian receives the Weather Page from the Penn State Department of Meteorology volunteer organization, the Campus Weather Service (CWS). The Department of Meteorology is considered to have the best programs in the country and is known for being academically rigorous. The New York Times entrusts its full-page weather spread to the Communications Group in the Department of Meteorology. Also, the Department houses the Pennsylvania State Climatology Office.

One of the CWS’s five branches focuses solely on producing the forecast for The Daily Collegian. Teams of five to ten student meteorologists work approximately two hours each night, Sunday to Thursday, to generate an accurate, free product for The Daily Collegian newspaper. The final product provides students at the University Park Campus with a four-day outlook, a forecast discussion, and almanac/climate information.

Over the past several years, the editors of The Daily Collegian have drastically cut the Weather Page removing sections like the Special Weather Feature. On numerous occasions, The Daily Collegian has printed the wrong forecast, changed the graphics, or given credit to the wrong shift members.

On Wednesday, Collegian editors and managers removed Saturday’s forecast, chopped off the last few sentences of the forecast discussion, and removed the names of the individuals who created the product as a means to make room for more news stories on the page.

Sadly, The Daily Collegian is removing information from the most accurate forecast in the State College area. The shift managers and vice-president of The Daily Collegian branch of the CWS have maintained statistics on forecasts generated by each shift, and compared the forecasts against the numerical weather prediction models and professional service providers. Through the statistics, the branch has found that the CWS forecast is consistently the most accurate in Happy Valley. This accuracy stems from the fact that CWS focuses on one location and not the entire nation. The professional service providers cannot devote the resources to a site-specific forecast.

I hope that the editors of The Daily Collegian will reconsider before they criticize members of the Campus Weather Service in the future.

February 2009 – Pennsylvania Weather Recap

Please note that the following summary was written for the Pennsylvania State Climate Office. Give credit to the Climate Office's "The Pennsylvania Observer" publication.

In Punxsutawney, Pa, the world's most famous groundhog, Punxsutawney Phil, spotted his shadow on February 2nd which is supposed to translate to six more weeks of winter. With the weather Pennsylvanians experienced at the beginning of the month, this long range forecast seemed mighty believable.

Much of the eastern part of the Commonwealth saw significant snow accumulation on February 3rd through the 4th as the first Nor' Easter of the year slid up the coast. Stations in the southeastern Pennsylvania region reported snowfall totals averaging from 4” to 6” (10-15cm) with isolated bands of snow totaling 8” to 10” (20-25cm). After the system moved out of the region, cold air from Canada moved into the Commonwealth on February 5th and 6th pushing lows down to the negative digits in some parts. Bradford Regional Airport (KBFD) recorded a low temperature of -11F/-24C during the evening hours of February 5th.

Things drastically changed by the weekend of February 7th as warmer air moved into the region preceding the next low pressure system. The warming trend continued through February 11th with temperatures reaching highs in the low 50s (10-12C) to upper 60s (near 20C) across much of the Commonwealth. Philadelphia International Airport (KPHL) reported a high temperature of 69F/21C on February 11th. New record highs were set for Williamsport, Harrisburg, Allentown, Reading, and Philadelphia on both the 11th and 12th.

Temperatures remained above freezing while the low moved through Pennsylvania during the nighttime hours of the 11th and 12th. Although snow and ice were not a problem, winds ravaged the Commonwealth. The Storm Prediction Center’s records showed twenty severe weather reports of wind damage from just the western part of Pennsylvania. The average gusting winds associated with the system ranged from 50 to 60mph (20-25m/s).

Pleasant conditions developed across the Commonwealth making for an enjoyable Valentine’s Day and President’s Day weekend. This pattern changed on the 18th and 19th as a low-pressure system trekked northeast along the Appalachian Mountains bringing light to moderate snow showers to Pennsylvania. Much of the Commonwealth received 0.5 to 5 inches (1-12cm) of snow with the liquid equivalent ranging from 0.1 to 0.6 inches (3-18mm).

On George Washington’s birthday, February 22nd, a clipper system passed through the region bringing snow to the western half of the Commonwealth. After a minor cool down from the 23rd to the 25th, much of Pennsylvania saw a return to above-average temperatures.
For the month of February, the Commonwealth had maximum and minimum temperatures that did not depart much from the mean (most sections were within 1F/0.4C of normal). However, precipitation was a different story.

Much of the region measured below normal precipitation. Harrisburg was 2.33 inches below the average for the month. The National Weather Service Cooperative Observer site located at Chalk Hill in Fayette County recorded the maximum total precipitation of 3.52 inches for the month of February. The maximum total snowfall recorded was 34 inches in Laurel Summit, Somerset County.

Nor'easter Anyone???

Could this be our first Nor'easter of the season? I feel it is pretty safe to say that we will see a nor'easter Monday night into Tuesday for this coming week, but there is one big question. Who is getting the snow and how much will they get? This may seem like a classic question, but the models have sent this storm all over the maps. I hope that by Sunday night some of my concerns are addressed by the model runs. Plan for an in depth discussion and possibly the weather blog's first podcast sometime this weekend.

Messy Winter Storm Coming!

Good evening everyone. We have a very interesting weather situation unfolding during the course of the day tomorrow through Wednesday for the State College area (and rest of Northeast). And of course, this winter storm system will not be clear-cut at all (just like every other one this season). Yet again, Central PA will not see JUST snow with this event as a change to sleet/frz rn for some portions of the area seems likely. So, let's take a look at what is currently going on:
Above is the current surface weather map for the US (courtesy of the HPC division of NOAA). We have a nice dome of 1036mb High pressure moving over the plains currently. This will move through the northern part of the country tonight and tomorrow bringing fresh cold air with it. To the south, in 4 corners region, lies the storm that will move NE tomorrow and bring snow with it.

The problem with the forecast (as always) is how much warm air gets brought into the upper levels of the atmosphere. We will have fresh cold air at the surface but the High pressure system will be moving out into the Atlantic during the day on Wednesday. This is not a great set-up for a major snowstorm. However, there is still a lot of potential here and certainly the possibility of a satisfying storm for the State College area.

The models have finally trended together and are close on a solution. They are not in total agreement but they are a whole lot closer than a day or 2 days ago. We'll take a look at the GFS, NAM/WRF, and the CMC (using the 12z runs for continuity...and the fact that the 18z runs are not the greatest).

12z GFS (for KUNV): Moderate snow develops after midnight on Tuesday night as the LOW moves through TN. Thicknesses are 539 dm which is barely cold enough to support snow BUT the 850 mb temps are nicely below freezing at -4.9 degrees C. As the snow intensifies toward daybreak on Wednesday, warm air is making an intrusion in the upper levels and thicknesses go up to 540 dm which is right on the border for snow (850 mb temps are borderline but still below freezing). The LOW is now over Norther VA and exits over Cape May during the afternoon on Wed. We get about .7o inches of QPF from this run which would be just over 7" of snow if it remained all snow. What concerns me is the placement of the 850 mb LOW. It goes over Northwestern PA and you don't want to be on the S side of the 850 mb LOW if you want to get the best snows. This tells me that the GFS says we will go over to sleet for a bit even though thicknesses remain marginal. Verbatim, the GFS gives us 4-8" (probably more on the 4/5" range with sleet mixing in).

850mb Heights 48 HR Forecast (HPC/NOAA)

12z NAM/WRF (for KUNV): The NAM is a bit slower than the GFS and brings precip in around daybreak (or a bit before) on Wednesday. The overall idea of the NAM is very similar to the GFS except the LOW tracks a bit further North which ends up giving us a little more warm air to deal with. Thicknesses climb to 541 at one point during the storm and the NAM even shows the surface warming to 32.1 degrees F. I find this hard to believe giving the good cold air damming situation and the fresh cold air we will be getting tomorrow. I'm confident that we will never get above freezing at the surface. Basically, the NAM wants to through a mostly sleet storm at us with about 1-3" of snow on the front end. As usual, the NAM is wetter with .90 inches of QPF. I think this is a bit overdone (although we do have a nice SW flow).

6 Hr Precip/850mb Temps 54hr Prog NAM (HPC/NOAA)

12z CMC (for KUNV): The CMC is the furthest north of the 3 models and tracks the LOW through KY, WV, over Allentown PA, and over Boston. As such, we REALLY warm the mid-levels of the atmosphere and go to sleet and most likely freezing rain for a lot of the storm. Storm QPF totals look about the same as the GFS.

My thinking: I'm going to go with a blend of the GFS and NAM and lean a bit more toward the GFS at this point. I think the NAM is too overdone with the QPF (it usually is) and I also think it gets rid of the cold air too quickly (also another bias of the model). The GFS to me has been the most consistent all along for this storm and in addition, the SREF ensemble mean leans toward the GFS as well.

Bottom line: Snow will develop around or a bit after midnight on Tuesday night and continue until about mid afternoon on Wednesday. We will definitely start off as all snow and probably pick up a quick 2-4" inches before any change over occurs. I DO think KUNV will go to sleet for a time and cut down on accumulations. I hope I'm wrong but it's hard for me to buy into all snow with the track of the 850 mb low. Around daybreak I think KUNV changes to a mix of snow and sleet and we pick up about 1-3" of that mess. And as the system moves out maybe and inch or two of snow. So, in the end, my call is for 4-7" of snow/sleet accumulation in State College. Best guess amount is 5".

Have a good night!

PS For those in the NYC area. I think NW of I-287 will see about 3-6". Far NW NJ and the Poconos will see 4-8" (local 10" in the Poconos). And NYC itself will see about 2-4" (mostly at the beginning of the storm).

Winter Storm on the Way!

I hope everyone had a great holiday season and New Year! I know I did! I had the opportunity to travel to Pasadena, CA and the Rose Bowl with the Penn State Blue Band. It was an awesome experience. Now on to the weather.

We have certainly had our share of sleet storms and wintry mix in State College this winter. We seem to have trouble getting a good 4-8" all snow event. Each time we have moisture coming our way, the LO has come to close to the area and we end up with warm air intruding in the upper levels while Cold Air Damming (CAD) in our area remains strong at the surface. Result: SLEET. Well, this drought may be about to end on Friday night and Saturday!

Currently, we have a nice dome of cold air (-10 degrees C at 850mb) moving over our area. We will then see the southern and northern jet streams partially phase and create a nice area of LO pressure over the Southern Ohio Valley on late Friday. The LO will move East through VA on Saturday and off the DE and NJ coast by early Sunday morning. There is fairly good agreement among the models at the current time with the latest (0z) NAM coming into line with the 12z and 18z GFS runs. Below is the 54 hr NAM from the 0z suite:

At this point, it looks like the cold air will hold strong and the track of the LO will be far enough south for KUNV to remain all snow. The 850mb LO is a little to close for comfort but soundings show all snow at this point.

Overall, I am extremely confident about this storm system being a good snow event for a line 50 miles either side of I-80 through PA and NJ. As an early call, I'm going to forecast 3-6" for that area with localized amounts in the 6-8" range. The NAM usually overdoes precip and I don't like it's ~.75 QPF. Yes this system has southern stream moisture with it, but I can't see that much liquid. I like the GFS's QPF output a lot better. .5 inches and a little greater seems much more reasonable.

I hope the 0z run of the GFS doesn't through a curveball into the equation. The only outlier is the Euro which is usually better in longer range situations anyway. So, for now, I like my early forecast and think KUNV will remain all snow (the NWS even had a Winter Storm Watch out early this afternoon). Precip should end at state college before midnight on Saturday night.

Have a good one everyone!