The Northeast Weather Blog...

Coastal Storm...

Posted by: Zachary Labe, 07:49 PM GMT del 24 Settembre 2008

Invest 94L (Coastal Storm)...

Satellite Picture...

(Courtesy of Penn State EWall)

First Thoughts...
My forecast has stayed pretty consistent the last couple of days with this complex scenerio. And so far I do not think I need to make any changes. The EURO model is still my model of choice as sort of an analog adding to my forecast. I was not sure if I was going to be able to create a new blog, but I decided that this was going to be a high impact event for late this week into the weekend. The sections below should take care of all forecasts and impacts for this event. A few things really excite me about this possibility because we are already beginning to potentially see where storm tracks may set up for the winter. Many people say it is too early for definite storm tracks to be patternized like those in September, but I think this may be a picture of what we may face down the road. Currently this storm is an Invest, 94L, and sitting off the Carolina's coastline moving westward towards inland. It is fighting some dry air and light shear, but still I cannot rule out a chance it develops into a tropical system or subtropical system. This sort of reminds me of Subtropical Storm Andrea which sat off the southeast coastline and caused lots of beach erosion and gusty winds. But this low pressure will move inland and cause areas of heavy rain also. I am looking at a storm track up the east coast as a trough pulls it north and then northeastward. Impacts with this storm I think will be quite similar to what many faced with Tropical Storm Hanna in terms of wind, rain, and wave action. Should be an interesting beach weekend with already surf being reported quite high near Ocean City, MD. Tight pressure gradient will also be felt as the high pressure pulls to the northeast in Northern New England currently. I hope to have people relay storm reports in this blog across the region and help to add to current forecast ideas. This blog is still under construction. Have a great day!!!

Current Advisories...

(Courtesy of NOAA)

Daily impacts...
This is going to be an extended period of high-impact weather coming late this week into the first half of the weekend with heavy rain, gusty winds, some severe weather, and coastal flooding. This will last from Thursday through Saturday night for effects on the Pennsylvania area. I decided not to make rain or wind maps for this storm, since I did not have the time today. But anyways here is my forecast for each of the impacts.

Heavy rain- Rainfall will be one of the primary threats from this event here in Pennsylvania. Now I have seen from the past that QPF is high overestimated across the Middle Atlantic during tropical events, so I am going to take a more reasonable forecast with a widespread 1-2inches for southcentral, to eastern, to northeastern Pennsylvania. There will be isolated higher amounts, but I am not anticipating any extended periods of very heavy rain. It should be a steady, moderate, stratiform type rainfall. Orographic lift may aid some rain totals in the Poconos and the southcentral mountains. Highest totals will be found along MD, DE, and NJ border counties.

Winds- Winds aloft will be quite strong, but they will have a hard time mixing down to the surface. Higher elevations of the southcentral Mountains, such as South Mountain will have some pretty strong winds with gusts near 45mph on the highest of the ridge tops. Laural highlands will also get gusty winds. Most valley locations will escape from the stronger winds. Now areas along the coastline will also see strong winds with gusts near 50mph, but not too much strong than that. With subtropical systems, the wind shield in not as compact as a purely tropical system.

Severe Weather- As with any system with somewhat tropical origins there is always the chance of an isolated tornado or wet downburst. We saw that this was the case with Hanna in Allentown, PA where an EF-1 unexpectedly touched down. Overall though I really do not anticipate any severe weather reports in the region, but I just wanted to highlight that the threat is there.

Storm Surge- A steady onshore flow for several days will result in consistent pushing of water over the beaches, especially during high tide. Waves will be in the general 5-10ft height during the height of the storm and a very higher waves will remain offshore. I think a 1-3ft water rise can be expected for areas along the Chesapeake. There will be less of a storm surge than there was with Hanna.

Overall this storm is less of a threat than Hanna was as there will be less severity of the impacts. This system is also subtropical, so the organization of the system is a little different. Typically the wind shield with subtropical systems is larger, but weaker. Also there usually is less of heavy rain rates with subtropical systems. So we will have to see what this storm does and if 93L has any impacts on the Northeast. Check back for more updates throughout the next couple of days.

"Radar for Central Pennsylvania"

"Radar for Eastern Pennsylvania"

Current Surface Map...

(Courtesy of Penn State EWall)

Current Weather Map...
A surge of high anomalies of moisture with PWATs near 2inches is quicking advancing north-northwest over the southeast and Middle Atlantic. Dewpoints will be on the rise along with a cirrus cloud deck overnight Wednesday night. As the subtropical low continues to linger off the North Carolina coastline, it will start to have winds turn easterly with a strong onshore flow for Thursday bringing in cooler temperatures with also a low LIFR stratus deck with ceilings as low as 500ft. High pressure will continue to move northeastward off towards to Canadian Maritimes, but a tight pressure gradient will develop. GFS 925mb charts indicate that winds aloft will near 45knots, but it does not look likely the most of those winds will mix down to the surface. Ridgetops though with elevations of 1500ft will feel some strong winds on Thursday and coastal areas may also see some strong winds. Moisture will continue to funnel in off the Atlantic and several shields of rainfall will develop varying slightly in intensity. The center of the low will begin to pull to the north and then northeastward as a cold front approaches from the west with another trough. The front will be very slow moving. For Friday the low pressure should be over the Tidewaters of Virginia causing the heaviest rainfall to fall to the northwest of the center which will be right along the area just east of the Appalachians and sort of close to the I-95 corridor. Winds will remain easterly, but begin to calm down throughout the day. Low stratus may keep a hold on the temperatures with them possibily in the 50s for highs on Friday. The heaviest time period for rain will be Friday night and then by Saturday the rain begins to die out, but low stratus will remain over the region. This entire storm system will be very similar to typical coastal lows in months such as late April and May. Some of the other sections in this blog will contain more details on the impacts. But above is the general setup.

Current Water Vapor Loop...

(Courtesy of Penn State EWall)

Computer model forecasts...
Looking at the computer models I still feel the EURO has the best feel for this storm with location and strength of the low pressure system. The NAM also seemed to forecast this system pretty well, but slightly too strong when coming ashore. GFS seems to be suffering from some major convective feedback errors with just blotches of high QPF all over the map. I like the HPC rainfall map as it incorporates the orographic lifting mechanism for parts of southcentral Pennsylvania.

SREF model also seems to have a good hold on precipitation totals, possibly a little too far west though on some of the high QPF. This has been quite a complex scenerio so I would not be surprised to see a few surprises along the way with this storm. Looks like highest rainfall totals will be in counties such as Adams, Franklin, York, Lancaster, Chester, Delaware, Philadelphia, Bucks, and Montgomery. Franklin and Adams Counties will get some of that extra orographic lift added to their precipitation totals. I would not be surprised to see an isolated 4inch rainfall total reported. A concern of mine though right now is that the precipitation shield is pretty small right now near the subtropical low, but it is expanding, so I guess we will have to wait and see. Looking at the model soundings from the GFS it prints out a max rainfall total of nearly 4inches at Philadelphia International Airport... Link. I think though some of that total is due to the convective feedback errors the model is suffering.

Final Thoughts...
Looking ahead towards late this weekend, I am looking like I will not have the time to get another blog out until next Tuesday. So this final thoughts section will cover the forecasts from Sunday through Tuesday and beyond into the long term. From busy period again starting early next week as a very strong cold front works into the region behind this coastal storm. High pressure moves over the region for Monday bringing once again cooler than normal temperatures along with dry humidity levels. Another cold front quickly approaches for Tuesday with a very, very deep and amplified trough over much of the Midwest and Northeast with some of the coolest weather of the season. Models have been back and forth with solutions from a Appalachian runner type storm system with heavy rain, or another east coast coastal storm. This reminds me of a winter time type scenerio. This storm system may impact midweek. The deep trough will cause some very low isothermal layers with possibily the 0C line as far south as Pennsylvania. After high pressure moves over the region after what ever storm system forms, then we could see some widespread killing frosts over the region. I still am holding to my forecast of an early October frost or freeze widespread over Pennsylvania. NAO levels remain towards negative and very high PNA levels remain over the western Rockies with a anomalious large ridge with warmer than normal temperatures. Global models like the GFS and EURO have been forecasting this scenerio for quite a while now. So overall the long term pattern looks quite unsettled and cool. Also I just want to lastly mention, I cannot rule out a few snowflakes across far Northern England during this time period as upper levels and lower levels support ice crystal growth down to elevations of 4,000ft. So very interesting period is ahead. Winter is coming for those of you who do not want to admit it, lol. Have a great day!!!

Forecast Model Links
-NAM model 12z...Link
-GFS model 12z...Link
-NMM model 12z...Link
-SREF model 9z...Link

Severe Weather Links
-Atmospheric Soundings Skewt T charts...Link
-SPC Mesoscale Analysis Pages...Link
-Public Spotter Reports for State College NWS...Link
-Severe Weather Model Forecast indices...Link
-Severe Weather Parameter Definitions...Link

Flooding Links
-Automated Pennsylvania Rainfall Recording Stations...Link
-Flash Flooding Guidance...Link
-HPC Forecasts for Excessive Rainfall...Link
-Hydrology Predictions for Lakes, Rivers, and Streams...Link

Categories: Tropics

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101. Zachary Labe 01:22 PM GMT del 28 Settembre 2008
TheRasberryPatch- The cutoff low has moved slightly farther north and the precipitation remains with it. So now it is spinning in the typical counter-clockwise flow. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

102. pittsburghnurse 01:37 PM GMT del 28 Settembre 2008
Mornin' Blizz. Yes, we did wring out a nice amount of rain here in the Burgh. We were an inch short, and an inch is what we got. Happy camper here. What's this about a cold December? What about snow? I love December snow. Member Since: Ottobre 14, 2006 Posts: 1 Comments: 638

103. Zachary Labe 01:47 PM GMT del 28 Settembre 2008
pittsburghnurse- Good morning!!! Glad to hear you received some rain out that way. Hasn't it been like 18days since Pittsburgh saw measurable rain. As for this winter overall I think it will be colder than normal with average snowfall maybe even a little above average. I also think this year percentages for a white christmas are higher than historical means across the state. Also looking at all of the models and teleconnections it appears like December will be the coldest month of the winter, so with cold comes the snow. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

104. JDinWPA 02:12 PM GMT del 28 Settembre 2008
Morning Bliz. We are still holding at a trace of rain. Had some pretty good misting going this morning. lol. Hit and miss. Approximately how cold would a colder than average December be? 5 - 10 degrees? More? I always wish for a green Christmas because either I'm traveling or someone is traveling to my house. Besides white Christmases are the norm here anyway. It's nice to have a break in the monotony! lol.

105. Zachary Labe 02:24 PM GMT del 28 Settembre 2008
JDinWPA- Wow, that rain over the southern part of your county must have really held stationary. Many areas saw up to 1inch of rain in southwestern and western Pennsylvania. If I would have to take an estimate I would say 3-5degrees colder than normal for December. 10degrees would nearly be record breaking cold. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

106. TheRasberryPatch 05:52 PM GMT del 28 Settembre 2008
getting a heavy thunderstorm at the moment. 0.50" the last 20 mins. as the rain gauge is saying 'its raining cats and dogs' Member Since: Gennaio 26, 2007 Posts: 72 Comments: 5637

108. Zachary Labe 08:10 PM GMT del 28 Settembre 2008
TheRasberryPatch- 1.49inches of rainfall total this weekend. It was quite a washout. I did not get up to Hawk Mountain today as the ridges were shrouded in fog and it rained a majority of the day. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

109. TheRasberryPatch 09:55 PM GMT del 28 Settembre 2008
Blizz - I got 1.00" since midnight and most of that came this afternoon. between 2pm and 3pm i got 0.72" of rain. 1.74" of rain since Thursday when the rain started and 1.37" for the weekend Member Since: Gennaio 26, 2007 Posts: 72 Comments: 5637

110. Zachary Labe 10:21 PM GMT del 28 Settembre 2008
TheRasberryPatch- Except for extreme northwestern and western Pennsylvania, almost everybody saw some pretty decent measurable rainfall nearly 1inch+. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

111. TheRasberryPatch 11:33 PM GMT del 28 Settembre 2008
Blizz - it was definitel some beneficial rain. we really haven't had much for septmeber, except from hanna. now on to the week and some upcoming cold air? frost? Member Since: Gennaio 26, 2007 Posts: 72 Comments: 5637

112. cchamp6 11:37 PM GMT del 28 Settembre 2008
Blizz, Raining again!! Still coming down. .85" today, 2.52" since friday and 10.25" since Hanna. Needless to say, the ground is saturated. Member Since: Dicembre 21, 2006 Posts: 5 Comments: 1543

113. cchamp6 11:57 PM GMT del 28 Settembre 2008
AHHHHH, correction 1.30" today and pouring down. Member Since: Dicembre 21, 2006 Posts: 5 Comments: 1543

114. Zachary Labe 12:20 AM GMT del 29 Settembre 2008
TheRasberryPatch- Yep that was a great beneficial rain for the last week in September. Can you believe October is just around the corner this week? Any leaves changing your way yet? Maples are really turning red here, even the mature ones. Yep I am still expecting areas of frost in our area for end of next week. It will not be a freeze, but should be a mid to upper 30s frost. cchamp6- Wow, that is something. I wonder if this wet pattern will continue for your area through the rest of fall. Typically fall is the driest of seasons across much of the nation. Thanks for your report! Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

115. cchamp6 01:01 AM GMT del 29 Settembre 2008
Stopped raining 1.46", 10.86 on the month. Member Since: Dicembre 21, 2006 Posts: 5 Comments: 1543

116. TheRasberryPatch 01:08 AM GMT del 29 Settembre 2008
Blizz - no signs of autumn here. leaves on the trees are green. back in before hanna they were starting to change, but that was probably because of very dry conditions. I didn't cut my grass from July 31 until Sept. 11. the leaves are very green right now. i don't even see any change going through Hershey. the only signs i see would be soybean is brown and the corn is dry ready to be cut. Member Since: Gennaio 26, 2007 Posts: 72 Comments: 5637

117. Fshhead 06:05 AM GMT del 29 Settembre 2008
Nice link you dropped off in my blog. THANX man, the place sounds really cool... It POURED here today for a few hours. Parking lot at work was under water LOL I am guessing our tropical visitor from down south came a knockin'? Have not been keeping a close eye on it cause of all the political stuff going on right now & the NHC said it would not develop but, that Fla probably was going to get some rain out of it. LOL Man did we ever.... Member Since: novembre 19, 2005 Posts: 9 Comments: 9960

118. Zachary Labe 10:20 AM GMT del 29 Settembre 2008
cchamp6- 1.49inches remains the total here. TheRasberryPatch- Well that is interesting, maples and birch are really just beginning to shed some of their color this weekend here. Fshhead- Yep, I thought that sounded to be pretty neat. It seems like Florida is always getting tropical visitors this time of year. I bet you guys down there in Florida are counting down the days until tropical season is over. Thanks for stopping by! Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

119. Zachary Labe 07:08 PM GMT del 29 Settembre 2008
*New blog coming tomorrow. Member Since: Dicembre 14, 2007 Posts: 253 Comments:** 14299

120. TheRasberryPatch 08:21 PM GMT del 29 Settembre 2008
Blizz - i am up on a hill a bit and i can see the south facing mountains facing harrisburg and when the sun shines on it you see all green. no signs of autumn from south facing mountains. Member Since: Gennaio 26, 2007 Posts: 72 Comments: 5637

121. Zachary Labe 09:19 PM GMT del 29 Settembre 2008
TheRasberryPatch- I will try to get some pictures to post in the next couple of days. Mountain does not have many maples, mainly oaks. Mountain changes color very late in season. Last year it was in mid November. Also not too many birch around these areas, but up in the coal regions they have all turned. Seems valley maples that are mature and even newly planted have started to turn red. Here is the fall foliage report from last week... Link. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

122. hurigo 10:21 PM GMT del 29 Settembre 2008
Hey Blizz, I woke up this morning to the radio advising something about record rainfalls in Philly. Was I dreaming? Member Since: Ottobre 9, 2005 Posts: 97 Comments: 6610

123. Zachary Labe 10:26 PM GMT del 29 Settembre 2008
hurigo- Lol, I cannot find anything about record rains for Philadelphia. They have had 4.13inches of rain for September, which is above normal, but not record breaking. But other than that I do not think I can answer your question. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

124. hurigo 10:33 PM GMT del 29 Settembre 2008
Thanks for the facts, Blizz. Maybe I was somewhere in between dream land and reality. So, did anyone in your great wide state have any troublesome affects from no-named Carolina storm? Member Since: Ottobre 9, 2005 Posts: 97 Comments: 6610

125. Zachary Labe 10:35 PM GMT del 29 Settembre 2008
hurigo- Nope, at least I haven't heard any. It was a nice beneficial rain with one or two spots maxing out with 5inches of rain. But the ground was able to handle it. Also I wanted to thankyou for the friendly introduction about my blog to Hurugo's blog. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

126. hurigo 10:38 PM GMT del 29 Settembre 2008
Oh, you are most welcome, Blizz. I do so much enjoy your blog. As a northern southerner, I find it most helpful. Glad to know I can call on you to translate some of the difficult meteorological "stuff." Member Since: Ottobre 9, 2005 Posts: 97 Comments: 6610

127. Zachary Labe 10:40 PM GMT del 29 Settembre 2008
hurigo- Lol, thanks again. I have to go, appears like a beautiful evening is in store with a cool crisp temperature. Sun is already down below the mountain so getting dark already. Sort of sad, but yet I love this season. New blog tomorrow morning. Have a nice evening! Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

128. jthal57 10:56 PM GMT del 29 Settembre 2008
Blizzard- my trek out to State College was interesting. We saw a variety of fall colors traveling on I-80 from the Poconos out through the middle of the state. Things are more colorful in most places than here in Northampton County. Conditions were mostly cloudy all day in Happy Valley. I believe that is Mount Nittany shrouded in clouds?

129. Zachary Labe 11:30 PM GMT del 29 Settembre 2008
jthal57- Good evening!!! I remember last year traveling up rt. 322 and it seemed in the Middle Susquehanna Valley region and the Happy Valley area it seemed fall colors are always quite early. Thanks for the picture! Mountains were shrouded in fog here too. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

130. WeatherBobNut 12:21 AM GMT del 30 Settembre 2008
Good evening Blizz, what a difference a year makes! As i said earlier to you about my wife and kid out swimming a year ago...well, this Oct 2nd, looks like highs will be in the 50's....BIG change. This looks to me that this winters pattern may be the east be in a strong trough and we get a favorable storm track that sets up in the perfect location, right up the eastern seaboard. From studies that i've done in many past falls, every time it got this cool so early, we had a great snowy winter season ahead. I see the euro has a nice eastern storm around the 11th-13th....we'll see how that pans out...looking forward to your new blog in the morning. ttysoon. -Weather Bob

131. Zachary Labe 12:25 AM GMT del 30 Settembre 2008
WeatherBobNut- This troughing pattern really dominated most of the summer and even Spring and now Fall. Seems like an extended period of negative NAO for the most part. *I was typing up my new blog this evening for tomorrow and was taking a look at a few forecast grids for New England. Look what I came upon... Link. 10 Miles SW Keene Valley NY... Friday: A chance of rain and snow showers. Cloudy, with a high near 41. Chance of precipitation is 50%. Friday Night: A chance of snow showers. Cloudy, with a low around 26. Chance of precipitation is 30% This is the first forecast of snow in the NWS grids I have seen so far this fall. Member Since: Dicembre 14, 2007 Posts: 253 Comments:** 14299

132. weathergeek5 12:34 AM GMT del 30 Settembre 2008
I do have a feeling this fall and winter nor'easters will be in the news quite a few times. Member Since: Dicembre 25, 2005 Posts: 0 Comments: 1721

133. Zachary Labe 12:41 AM GMT del 30 Settembre 2008
weathergeek5- I sure hope so at least. I am ready for a 02-03 type winter. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

134. weathergeek5 12:57 AM GMT del 30 Settembre 2008
I am wanting a 1995-1996 winter. Member Since: Dicembre 25, 2005 Posts: 0 Comments: 1721

135. Zachary Labe 01:01 AM GMT del 30 Settembre 2008
weathergeek5- Yea that would be nice too, lol. So how much rain did your area end up with during this past cut-off low. I saw some nasty thunderstorms training over extreme southeastern Pennsylvania. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

136. weathergeek5 01:37 AM GMT del 30 Settembre 2008
We had some storms yesterday there were a few claps of thunder but not too bad. Member Since: Dicembre 25, 2005 Posts: 0 Comments: 1721

137. Zachary Labe 01:47 PM GMT del 30 Settembre 2008
weathergeek5- Similar conditions occured here too. Member Since: Dicembre 14, 2007 Posts: 253 Comments: 14299

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Cornell University- Atmospheric Sciences Student; Central PA SKYWARN Storm Spotter; American Meteorological Society Member; PA CoCoRaHS Branch Member

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Elevation:	520 ft
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